file which includes the original illustrations4 ,see #cafbg-;h4htm or #cafbg-;h4zip3 7https3_/_/www4gutenberg4org_/cache_/epu b_/#cafbg_/pg#cafbg-;images4html7 or 7https3_/_/www4gutenberg4org_/files_/#ca fbg_/cafbg-;h4zip7 ,the ,contemporary ,science ,series4 ,edited by ,havelock ,ellis4 ,,volcanoes3 ,,past ,,and ,,present4 ,illustration3 ,fig4 #a4--;,eruption of ,vesuvius1 #ahgb-ahgc ,,volcanoes3 ,,past ,,and ,,present4 by ,,edward ,,hull1 ,m4,a41 ,,ll4,d41 ,f4,r4,s4 ,examiner in ,geology to the ,university of ,london4 ,with #da ,illustrations and #d ,plates of ,rock-,sections4 ,london3 ,walter ,scott1 ,limited1 #bd1 ,warwick ,lane1 ,paternoster ,row4 #ahib4 ,,by ,,the ,,same ,,author4 ,the ,coal-fields of ,great ,britain3 their ,history1 ,structure1 and ,resources4 #dth edit4 7#ahha47 ,e4 ,stanford4 ,the ,physical ,history of the ,british ,isles4 ,with a ,dissertation on the ,origin of ,western ,europe and of the ,atlantic ,ocean4 7#ahhb47 ,e4 ,stanford4 ,the ,physical ,geology and ,geography of ,ireland4 #bnd edit4 7#ahia47 ,e4 ,stanford4 ,treatise on the ,building and ,ornamental ,stones of ,great ,britain and ,foreign ,countries4 7#ahgb47 ,macmillan and ,co4 ,memoir on the ,physical ,geology and ,geography of ,arabia-,petra1 ,palestine1 and adjoining ,districts4 7#ahhf47 ,committee of the ,palestine ,exploration ,fund4 ,mount ,seir1 ,sinai1 and ,western ,palestine4 ,being a ,narrative of a ,scientific ,expedition1 #ahhc-hd4 7#ahhe47 ,committee of the ,palestine ,exploration ,fund4 ,text-book of ,physiography4 7#ahhh47 ,c4 ,w4 ,deacon and ,co4 ,sketch of ,geological ,history4 7#ahhg47 ,c4 ,w4 ,deacon and ,co4 ,,preface4 ,it has not been my object to present in the following pages even an approximately complete description of the volcanic and seismic phenomena of the globe2 such an undertaking would involve an amount of labour which few would be bold enough to attempt2 nor would it be compatible with the aims of the ,contemporary ,science ,series4 ,i have rather chosen to illustrate the most recent conclusions regarding the phenomena and origin of volcanic action1 by the selection of examples drawn from the districts where these phenomena have been most carefully observed and recorded under the light of modern geological science4 ,i have also endeavoured to show1 by illustrations carried back into later geological epochs1 how the volcanic phenomena of the present day do not differ in kind1 though they may in degree1 from those of the past history of our globe4 ,for not only do the modes of eruption of volcanic materials in past geological times resemble those of the present or human epoch1 but the materials themselves are so similar in character that it is only in consequence of alterations in structure or composition which the original materials have undergone1 since their extrusion1 that any important distinctions can be recognised between the volcanic products of recent times and those of earlier periods4 ,i have1 finally1 endeavoured to find an answer to two interesting and important questions3 7#a7 ,are we now living in an epoch of extraordinary volcanic energy8--a question which such terrible outbursts as we have recently witnessed in ,japan1 the ,malay ,archipelago1 and even in ,italy1 naturally suggest2 and 7#b7 ,what is the ultimate cause of volcanic action8 ,on this latter point ,i am gratified to find that my conclusions are in accordance with those expounded by one who has been appropriately designated the ,nestor of ,modern ,geology1 ,professor ,prestwich4 ,within the last few years the study of the structure and composition of volcanic rocks1 by means of the microscope brought to bear on their translucent sections1 has added wonderfully to our knowledge of such rocks1 and has become a special branch of petrological investigation4 ,commenced by ,sorby1 and carried on by ,allport1 ,zirkel1 ,rosenbusch1 ,von ,lasaulx1 ,teall1 and many more enthusiastic students1 it has thrown a flood of light upon our knowledge of the mutual relations of the component minerals of igneous masses1 the alteration these minerals have undergone in some cases1 and the conditions under which they have been erupted and consolidated4 ,but nothing that has been observed has tended materially to alter conclusions arrived at by other processes of reasoning regarding volcanic phenomena1 and for these we have to fall back upon observations conducted in the field on a more or less large scale1 and carried on before1 during1 and after eruptions4 ,macroscopic and microscopic observations have to go hand in hand in the study of volcanic phenomena4 ,e4 ,h4 ,,contents4 ,,part ,i4 ,,introduction4 ,,page ,chap4 ,i4 ,historic ,notices of ,volcanic ,action #a-i ,,ii4 ,form1 ,structure1 and ,composition of ,volcanic ,mountains #aj-ai ,,iii4 ,lines and ,groups of ,active ,volcanic ,vents #bj-bi ,,iv4 ,mid-ocean ,volcanic ,islands #cj-dj ,,part ,,ii4 ,,european ,,volcanoes4 ,chap4 ,i4 ,vesuvius #da-fj ,,ii4 ,etna #fa-fh ,,iii4 ,the ,lipari ,islands1 ,stromboli #fi-ge ,,iv4 ,the ,santorin ,group #gf-hc ,v4 ,european ,extinct or ,dormant ,volcanoes #hd-ia ,,vi4 ,extinct ,volcanoes of ,central ,france #ib-aab ,,vii4 ,the ,volcanic ,district of the ,rhine ,valley #ac-abe ,,part ,,iii4 ,,dormant ,,or ,,moribund ,,volcanoes ,,of ,,other ,,parts ,,of ,,the ,,world4 ,chap4 ,i4 ,dormant ,volcanoes of ,palestine and ,arabia #abf-ace ,,ii4 ,the ,volcanic ,regions of ,north ,america #acf-ade ,,iii4 ,volcanoes of ,new ,zealand #adf-aec ,,part ,,iv4 ,,tertiary ,,volcanic ,,districts ,,of ,,the ,,british ,,isles4 ,chap4 ,i4 ,antrim #aed-aei ,,ii4 ,succession of ,volcanic ,eruptions #afj-aga ,,iii4 ,island of ,mull and ,adjoining ,coast #agb-agf ,,iv4 ,isle of ,skye #agg-agi ,v4 ,the ,scuir of ,eigg #ahj-ahd ,,vi4 ,isle of ,staffa #ahe-ahf ,,part ,v4 ,,pre-,,tertiary ,,volcanic ,,rocks4 ,chap4 ,i4 ,the ,deccan ,trap-series of ,india #ahg-ahi ,,ii4 ,abyssinian ,table-lands #aij-aic ,,iii4 ,cape ,colony #aid-aie ,,iv4 ,volcanic ,rocks of ,past ,geological ,periods of the ,british ,isles #aif-aii ,,part ,,vi4 ,,special ,,volcanic ,,and ,,seismic ,,phenomena4 ,chap4 ,i4 ,the ,eruption of ,krakatoa in #ahhc #bja-baf ,,ii4 ,earthquakes #bag-bbd ,,part ,,vii4 ,,volcanic ,,and ,,seismic ,,problems4 ,chap4 ,i4 ,the ,ultimate ,cause of ,volcanic ,action #bbe-bce ,,ii4 ,lunar ,volcanoes #bcf-beb ,,iii4 ,are we ,living in an ,epoch of ,special ,volcanic ,activity8 #bec-beg ,,appendix4 ,a ,brief ,account of the ,principal ,varieties of ,volcanic ,rocks #bei-bfe ,index #bfh ,,illustrations4 ,fig4 #a4 ,eruption of ,vesuvius1 #ahgb-gc ,frontispiece #b4 ,cotopaxi ,page #af #c4 ,volcanic ,cone of ,orizaba #ba ,map of the ,world1 showing ,active and ,extinct ,volcanoes #bc #d4 ,teneriffe1 seen from the ,ocean #ca #e4 ,view of the ,summit of ,teneriffe #ce #f4 ,probable ,aspect of ,vesuvius at ,beginning of ,christian ,era #dc #g4 ,view of ,vesuvius before #agfg #ej #h4 ,map of ,district bordering ,bay of ,naples #eb #i4 ,view of ,vesuvius in #ahgb #ec #aj4 ,ideal ,section through ,etna #fc #aa4 ,map of the ,lipari ,islands #gj #ab4 ,the ,island of ,vulcano in ,eruption #ga #ac4 ,ideal ,section through ,gulf of ,santorin #gf #ad4 ,bird's-eye ,view of ,gulf of ,santorin #gi #ae4 ,ground ,plan of ,rocca ,monfina #hj #af4 ,geological ,section of ,tiber ,valley at ,rome #hh #ag4 ,generalised ,section ,through the ,vale of ,clermont #ic ,fig4 #ah4 ,view of ,puy de ,dme and ,neighbouring ,volcanoes ,page #ie #ai4 ,mont ,demise1 seen from the ,s4,e4 #ajc #bj4 ,sketch ,map of ,rhenish ,area in the ,miocene ,epoch #aad #ba4 ,the ,volcanic ,range of the ,siebengebirge #aag #bb4 ,section of ,extinct ,crater of the ,roderberg #abj #bc4 ,plan and ,section of the ,laacher ,see #abb #bd4 ,extinct ,craters in the ,jauln #acj #be4 ,mount ,shasta #aci #bf4 ,forms of ,volcanic ,tuff-,cones1 ,auckland #adh #bg4 ,the ,white ,rocks1 ,portrush1 ,co4 ,antrim #aeg #bh4 ,section across the ,volcanic ,plateau of ,antrim #aei #bi4 ,section at ,templepatrick #afa #cj4 ,cliff above the ,giant's ,causeway #afc #ca4 ,the ,giant's ,causeway1 ,co4 ,antrim #afe #cb4 ,the ,chimneys1 ,north ,coast of ,antrim #aff #cc4 ,section at ,alt na ,searmoin1 ,mull #age #cd4 ,view of the ,scuir of ,eigg from the ,east #aha ,map of ,volcanic ,band of the ,moluccas #bjj #ce4 ,map of the ,krakatoa ,group of ,islands #bjc #cf4 ,section from ,verlaten ,island through ,krakatoa #bjd ,fig4 #cg4 ,isoseismals of the ,charleston ,earthquake ,page #bbc #ch4 ,photograph of the ,moon's ,surface #bda #ci4 ,portion of the ,moon's ,surface #bdc ,,plates4 ,i4 ,,ii4 ,magnified ,sections of ,vesuvian ,lavas4 ,,iii4 ,,iv4 ,magnified ,sections of ,volcanic ,rocks4 ,volcanoes3 ,past and ,present4 ,,part ,i4 ,,introduction4 ,,chapter ,i4 ,,historic ,,notices ,,of ,,volcanic ,,action4 ,there are no manifestations of the forces of ,nature more calculated to inspire us with feelings of awe and admiration than volcanic eruptions preceded or accompanied1 as they generally are1 by earthquake shocks4 ,few agents have been so destructive in their effects2 and to the real dangers which follow such terrestrial convulsions are to be added the feelings of uncertainty and revulsion which arise from the fact that the earth upon which we tread1 and which we have been accustomed to regard as the emblem of stability1 may become at any moment the agent of our destruction4 ,it is1 therefore1 not surprising that the ancient ,greeks1 who1 as well as the ,romans1 were close observers of the phenomena of ,nature1 should have investigated the causes of terrestrial disturbances1 and should have come to some conclusions upon them in accordance with the light they possessed4 ,these terrible forces presented to the ,greeks1 who clothed all the operations of ,nature in poetic imagery and deified her forces1 their poetical and mystical side2 and as there was a deity for every natural force1 so there was one for earthquakes and volcanoes4 ,vulcan1 the deformed son of ,juno 7whose name bears so strange a resemblance to that of the first artificer in iron of the ,bible1 ,tubal ,cain71 is condemned to pass his days under ,mount ,etna1 fabricating the thunderbolts of ,jove1 and arms for the gods and great heroes of antiquity4 ,the ,pythagoreans appear to have held the doctrine of a central fire 7meson pyr7 as the source of volcanic phenomena2 and in the ,dialogues of ,plato allusion is made to a subterranean reservoir of lava1 which1 according to ,simplicius1 was in accordance with the doctrine of the ,pythagoreans which ,plato was recounting4#a ,thucydides clearly describes the effect of earthquakes upon coast-lines of the ,grecian ,archipelago1 similar to that which took place in the case of the earthquake of ,lisbon1 the sea first retiring and afterwards inundating the shore4 ,pliny supposed that it was by earthquake avulsion that islands were naturally formed4 ,thus ,sicily was torn from ,italy1 ,cyprus from ,syria1 ,euboea from ,boeotia1 and the rest2 but this view was previously enunciated by ,aristotle in his ,peri kosmou1 where he states that earthquakes have torn to pieces many parts of the earth1 while lands have been converted into sea1 and that tracts once covered by the sea have been converted into dry land4 ,but the most philosophical views regarding terrestrial phenomena are those given by ,ovid as having been held by ,pythagoras 7about ,b4,c4 #ehj74 ,in the ,metamorphoses his views regarding the interchange of land and sea1 the effects of running water in eroding valleys1 the growth of deltas1 the effect of earthquakes in burying cities and diverting streams from their sources1 are remarkable anticipations of doctrines now generally held4#b ,but what most concerns us at present are his views regarding the changes which have come over volcanic mountains4 ,in his day ,vesuvius was dormant1 but ,etna was active2 so his illustrations are drawn from the latter mountain2 and in this connection he observes that volcanic vents shift their position4 ,there was a time1 he says1 when ,etna was not a burning mountain1 and the time will come when it will cease to burn2 whether it be that some caverns become closed up by the movements of the earth1 or others opened1 or whether the fuel is finally exhausted4#c ,strabo may be regarded as having originated the view1 now generally held1 that active volcanoes are safety-valves to the regions in which they are situated4 ,referring to the tradition recorded by ,pliny1 that ,sicily was torn from ,italy by an earthquake1 he observes that the land near the sea in those parts was rarely shaken by earthquakes1 since there are now orifices whereby fire and ignited matters and waters escape2 but formerly1 when the volcanoes of ,etna1 the ,lipari ,islands1 ,ischia1 and others were closed up1 the imprisoned fire and wind might have produced far more violent movements4#d ,the account of the first recorded eruption of ,vesuvius has been graphically related by the younger ,pliny in his two letters to ,tacitus1 to which ,i shall have occasion to refer further on4#e ,these bring down the references to volcanic phenomena amongst ancient authors to the commencement of the ,christian era2 from all of which we may infer that the more enlightened philosophers of antiquity had a general idea that eruptions had their origin in a central fire within the interior of the earth1 that volcanic mountains were liable to become dormant for long periods1 and afterwards to break out into renewed activity1 that there existed a connection between volcanic action and earthquakes1 and that volcanoes are safety-valves for the regions around4 ,it is unnecessary that ,i should pursue the historical sketch further4 ,those who wish to know the views of writers of the ,middle ,ages will find them recorded by ,sir ,charles ,lyell4#f ,the long controversy carried on during the latter part of the eighteenth century between ,neptunists1 led by ,werner on the one side1 and ,vulcanists1 led by ,hutton and ,playfair on the other1 regarding the origin of such rocks as granite and basalt1 was finally brought to a close by the triumph of the ,vulcanists1 who demonstrated that such rocks are the result of igneous fusion2 and that in the cases of basalt and its congeners1 they are being extruded from volcanic vents at the present day4 ,the general principles for the classification of rocks as recognised in modern science may be regarded as having been finally established by ,james ,hutton1 of ,edinburgh1 in his ,theory of the ,earth1#g while they were illustrated and defended by ,professor ,playfair in his work entitled1 ,illustrations of the ,huttonian ,theory of the ,earth1#h although other observers1 such as ,desmarest1 ,collini1 and ,guettard1 had in other countries come to very clear views on this subject4 ,the following are some of the more important works on the phenomena of volcanoes and earthquakes published during the present century3--#i #a4 ,poulett ,scrope1 ,f4,r4,s41 ,considerations on ,volcanoes 7#ahbe74 ,this work is dedicated to ,lyell1 his fellow-worker in the same department of science1 and was undertaken1 as he says1 in order to help to dispel that signal delusion as to the mode of action of the subtelluric forces with which the ,elevation-,crater theory had mystified the geological world4 ,the second edition was published in #ahgb4 #b4 ,this was followed by the admirable work1 ,on the ,extinct ,volcanoes of ,central ,france1 published in #ahbf 7#bnd edition1 #aheh71 and is one of the most complete monographs on a special volcanic district ever written4 #c4 ,dr4 ,samuel ,hibbert1 ,history of the ,extinct ,volcanoes of the ,basin of ,neuwied on the ,lower ,rhine 7#ahcb74 ,dr4 ,hibbert's work is one of remarkable merit1 if we consider the time at which it was written4 ,for not only does it give a clear and detailed account of the volcanic phenomena of the ,eifel and the ,lower ,rhine1 but it anticipates the principles upon which modern writers account for the formation of river valleys and other physical features2 and in working out the physical history of the ,rhine valley below ,mainz1 and its connection with the extinct volcanoes which are found on both banks of that river1 he has taken very much the same line of reasoning which was some years afterwards adopted by ,sir ,a4 ,ramsay when dealing with the same subject4 ,it does not appear that the latter writer was aware of ,dr4 ,hibbert's treatise4 #d4 ,leopold von ,buch1 ,description ,physique des ,iles ,canaries 7#ahbe71 translated from the original by ,c4 ,boulanger 7#ahcf72 ,geognostische ,reise 7,berlin1 #ahji71 #b vols42 and ,reise durch ,italien 7#ahji74 ,from a large number of writings on volcanoes by this distinguished traveller1 whom ,alexander von ,humboldt calls dem geistreichen ,forscher der ,natur1 the above are selected as being the most important4 ,that on the ,canaries is accompanied by a large atlas1 in which the volcanoes of ,teneriffe1 ,palma1 and ,lancerote1 with some others1 are elaborately represented1 and are considered to bear out the author's views regarding the formation of volcanic cones by elevation or upheaval4 ,the works dealing with the volcanic phenomena of ,central and ,southern ,italy are also written with the object1 in part at least1 of illustrating and supporting the same theoretical views2 with these we have to deal in the next chapter4 #e4 ,dr4 ,charles ,daubeny1 ,f4,r4,s41 ,description of ,active and ,extinct ,volcanoes1 of ,earthquakes1 and of ,thermal ,springs1 with remarks on the causes of these phenomena1 the character of their respective products1 and their influence on the past and present condition of the globe 7#bnd edition1 #ahdh74 ,in this work the author gives detailed descriptions of almost all the known volcanic districts of the globe1 and defends what is called the chemical theory of volcanic action--a theory at one time held by ,sir ,humphrey ,davy4 #f4 ,wolfgang ,sartorius von ,waltershausen1 ,der tna4 ,this work possesses a melancholy interest from the fact that its distinguished author did not live to see its publication4 ,von ,waltershausen1 having spent several years in making an elaborate survey of ,etna1 produced an atlas containing numerous detailed maps1 views1 and drawings of this mountain and its surroundings1 which were published at ,weimar by ,engelmann in #aheh4 ,a description in ,,ms4 to accompany the atlas was also prepared1 but before it was printed1 the author died1 on the #afth ,october #ahgf4 ,the ,,ms4 having been put into the hands of the late ,professor ,arnold von ,lasaulx by the publisher of the atlas1 it was subsequently brought out under the care of this distinguished petrologist1 who was so fully fitted for an undertaking of this kind4 #g4 ,sir ,charles ,lyell in his ,principles of ,geology#aj devotes several chapters to the consideration of volcanic phenomena1 in which1 being in harmony with the views of his friend1 ,poulett ,scrope1 he combats the elevation theory of ,von ,buch1 as applied to the formation of volcanic mountains1 holding that they are built up of ashes1 stones1 and scori blown out of the throat of the volcano and piled around the orifice in a conical form4 ,together with these materials are sheets of lava extruded in a molten condition from the sides or throat of the crater itself4 #h4 ,professor ,j4 ,w4 ,judd1 ,f4,r4,s41 in his able work entitled1 ,volcanoes3 ,what they are1 and what they teach1#aa has furnished the student of vulcanicity with a very complete manual of a general character on the subject4 ,the author1 having extensive personal acquaintance with the volcanoes of the south of ,europe and the volcanic rocks of the ,british ,isles1 was well equipped for undertaking a work of the kind2 and in it he supports the views of ,lyell and ,scrope regarding the mode of formation of volcanic mountains4 #i4 ,sir ,archibald ,geikie1 ,f4,r4,s41 in his elaborate monograph#ab on the ,tertiary ,volcanic ,rocks of the ,british ,isles1 has recorded his views regarding the origin and succession of the plateau basalts and associated rocks over the region extending from the north of ,ireland to the ,inner ,hebrides2 and in dealing with these districts in the following pages ,i have made extensive use of his observations and conclusions4 #aj4 ,report published by the ,royal ,society on the ,eruption of ,krakatoa--drawn up by several authors 7#ahhe7--;and the work on the same subject by ,chev4 ,verbeek1 and published by the ,government of the ,netherlands 7#ahhf74 ,in these works all the phenomena connected with the extraordinary eruptions of ,krakatoa in #ahhc are carefully noted and scientifically discussed1 and illustrated by maps and drawings4 #aa4 ,the ,charleston ,earthquake of ,august #ca1 #ahhf1 by ,captain ,clarence ,edward ,dutton1 ,u4,s4 ,ordnance ,corps4 ,ninth ,annual ,report of the ,united ,states ,geological ,survey1 #ahhg-hh1 with maps and illustrations4 #ab4 ,amongst other works which may be consulted with advantage is that of ,mr4 ,t4 ,mellard ,reade on ,the ,origin of ,mountain ,ranges2 the ,rev4 ,osmond ,fisher's ,physics of the ,earth2 ,professor ,g4 ,h4 ,darwin and ,mr4 ,c4 ,davison on ,the ,internal ,tension of the ,earth's ,crust1 ,philosophical ,transactions of the ,royal ,society1 vol4 #agh2 ,mr4 ,r4 ,mallet1 ,on the ,dynamics of ,earthquakes1 ,trans4 ,roy4 ,irish ,academy1 vol4 xxi42 ,professor ,o',reilly's ,catalogues of ,earthquakes1 ,trans4 ,roy4 ,irish ,academy1 vol4 xxviii4 7#ahhd and #ahhh72 and ,mr4 ,a4 ,ent4 ,gooch ,on the ,causes of ,volcanic ,action 7,london1 #ahij74 ,these and other authorities will be referred to in the text4 #a ,see ,julius ,schwarez ,on the ,failure of ,geological ,attempts made by the ,greeks4 7,edition #ahhh47 #b ,vidi ego1 quod fuerat quondam solidissima tellus1 ,esse fretum4 ,vidi factas ex quore terras3 ,et procul pelago conch jacuere marin2 ,et vetus inventa est in montibus anchora sumnis4 ,quodque fuit campus1 vallem de cursus aquarum ,fecit2 et eluvie mons est deductus in quor3 ,eque paludosa siccis humus aret arenis2 ,quque sitim tulerant1 stagnata paludibus hument4 ,hic fontes ,natura novos emissit1 at illuc ,clausit3 et antiquis concussa tremoribus orbis ,fulmina prosiliunt4444 --,lib4 xv4 #bfb4 #c ,nec1 qu sulfureis ardet fornacibus1 tne ,ignea semper erit2 neque enim fuit ignea semper4 ,nam1 sive est animal tellus1 et vivit1 habetque ,spiramenta locis flammam exhalantia multis2 ,spirandi mutare vias1 quotiesque movetur1 ,has finire potest1 illas aperire cavernas3 ,sive leves imis venti cohibentur in antris2 ,saxaque cum saxis4444 --,ibid41 #cdj4 #d ,strabo1 lib4 vi4 #e ,tacitus1 lib4 vi4 #af1 #bj4 #f ,principles of ,geology1 #aath edition1 vol4 i41 ch4 #c4 #g #b vols41 ,edin4 7#agie74 #h ,edin4 7#ahjb74 #i ,a more extended list of early works will be found in ,daubeny's ,volcanoes 7#ahdh74 #aj #aath edition 7#ahgb74 #aa #dth edition 7#ahhh74 #ab ,the ,history of ,volcanic ,action during the ,tertiary ,period in the ,british ,isles1 ,trans4 ,roy4 ,soc41 ,edin4 ,vol4 xxxv1 7#ahhh74 ,,chapter ,,ii4 ,,form1 ,,structure1 ,,and ,,composition ,,of ,,volcanic ,,mountains4 ,the conical form of a volcanic mountain is so generally recognised1 that many persons who have no intelligent acquaintance with geological phenomena are in the habit of attributing to all mountains having a conical form1 and especially if accompanied by a truncated apex1 a volcanic origin4 ,yet this is very far from being the fact1 as some varieties of rock1 such as quartzite1 not unfrequently assume this shape4 ,of such we have an example in the case of ,errigal1 a quartzite mountain in ,donegal1 nearly #cjjj feet high1 which bears a very near approach in form to a perfect cone or pyramid1 and yet is in no way connected1 as regards its origin or structure1 with volcanic phenomena4 ,another remarkable instance is that of ,schehallion in ,scotland1 also composed of quartz-rock2 and others may be found amongst the ranges of ,islay and ,jura1 described by ,sir ,a4 ,geikie4#a ,notwithstanding1 however1 such exceptions1 which might be greatly multiplied1 the majority of cone-shaped mountains over the globe have a volcanic origin4#b ,the origin of this form in each case is entirely distinct4 ,in the case of quartzite mountains1 the conical form is due to atmospheric influences acting on a rock of uniform composition1 traversed by numerous joints and fissures crossing each other at obtuse angles1 along which the rock breaks up and falls away1 so that the sides are always covered by angular shingle forming slopes corresponding to the angle of friction of the rock in question4 ,in the case of a volcanic mountain1 however1 the same form is due either to accumulation of fragmental material piled around the cup-shaped hollow1 or crater1 which is usually placed at the apex of the cone1 and owing to which it is bluntly terminated1 or else to the welling up from beneath of viscous matter in the manner presently to be described4 ,views of ,sir ,humphrey ,davy and ,l4 von ,buch4--,the question how a volcanic cone came to be formed was not settled without a long controversy carried on by several naturalists of eminence4 ,some of the earlier writers of modern times on the subject of vulcanicity--such as ,sir ,humphrey ,davy and ,leopold von ,buch--maintained that the conical form was due to upheaval by a force acting from below at a central focus1 whereby the materials of which the mountain is formed were forced to assume a qu-qu versal position--that is1 a position in which the materials dip away from the central focus in every direction4 ,but this view1 originally contested by ,scrope and ,lyell1 has now been generally abandoned4 ,it will be seen on reflection that if a series of strata of ashes1 tuff1 and lava1 originally horizontal1 or nearly so1 were to be forced upwards into a conical form by a central force1 the result would be the formation of a series of radiating fissures ever widening from the circumference towards the focus4 ,in the case of a large mountain such fissures1 whether filled with lava or otherwise1 would be of great breadth towards the focus1 or central crater1 and could not fail to make manifest beyond dispute their mechanical origin4 ,but no fissures of the kind here referred to are1 as a matter of fact1 to be observed4 ,those which do exist are too insignificant and too irregular in direction to be ascribed to such an origin2 so that the views of ,von ,buch and ,davy must be dismissed1 as being unsupported by observation1 and as untenable on dynamical grounds4 ,as a matter of fact1 the elevatory theory1 or the elevation-crater theory1 as it is called by ,scrope1 has been almost universally abandoned by writers on vulcanicity4 ,principal ,varieties of ,volcanic ,mountains as regards ,form4--,but whilst rejecting the elevatory theory1 it is necessary to bear in mind that volcanic cones and dome-shaped elevations have been formed in several distinct ways1 giving rise to varieties of structure essentially different4 ,two of the more general of these varieties of form1 the crater-cone and the dome1 are found in some districts1 as in ,auvergne1 side by side4 ,the crater-cone consists of beds or sheets of ashes1 lapilli1 and slag piled up in a conical form1 with a central crater 7or cup7 containing the principal pipe through which these materials have been erupted2 the dome1 of a variety of trachytic lava1 which has been extruded in a molten1 or viscous1 condition from a central pipe1 and in such cases there is no distinct crater4 ,there are other forms of volcanic mountains1 such as those built up of basaltic matter1 of which ,i shall have to speak hereafter1 but the two former varieties are the most prevalent2 and we may now proceed to consider the conditions under which the crater-cone volcanoes have been formed4 ,crateriform ,volcanic ,cones4--,of this class nearly all the active volcanoes of the ,mediterranean region--,etna1 ,vesuvius1 ,stromboli1 and the ,lipari ,islands--may be considered as representatives4 ,they consist essentially of masses of fragmental material1 which have from time to time been blown out of an orifice and piled up around with more or less regularity 7according to the force exerted1 and direction of the prevalent winds71 alternating with sheets of lava4 ,in this way mountains several thousand feet in height and of vast horizontal extent are formed4 ,the fragmental materials thus accumulated are of all sizes1 from the finest dust up to blocks many tons in weight1 the latter being naturally piled around nearest to the orifice4 ,the fine dust1 blown high into the air by the explosive force of the gases and vapours1 is often carried to great distances by the prevalent winds4 ,thus during the eruption of ,vesuvius in ,a4,d4 #dgb showers of ashes1 carried high into the air by the westerly wind1 fell over ,constantinople at a distance of #gej miles4#c ,these loose1 or partially consolidated1 fragmental materials are rudely stratified1 and slope downwards and outwards from the edge of the crater1 so as to present the appearance of what is known as the dip of stratified deposits which have been upraised from the horizontal position by terrestrial forces4 ,it was this excentrical arrangement which gave rise to the supposition that such volcanic ash-beds had been tilted up by a force acting in the direction of the volcanic throat1 or orifice of eruption4 ,the interior wall of ,monte di ,somma1 the original crater of ,vesuvius1 presents a good illustration of such fragmental beds4 ,i shall have occasion further on to describe more fully the structure of this remarkable mountain2 so that it will suffice to say here that this old prehistoric crater1 the walls of which enclose the modern cone of ,vesuvius1 is seen to be formed of irregular beds of ash1 scori1 and fragmental masses1 traversed by numerous dykes of lava1 and sloping away outwards towards the surrounding plains4 ,of similar materials are the flanks of ,etna composed1 even at great distances from the central crater2 the beds of ash and agglomerate sometimes alternating with sheets of solidified lava and traversed by dykes of similar material of later date1 injected from below through fissures formed during periods of eruptive energy4 ,numerous similar examples are to be observed in the ,auvergne region of ,central ,france and the ,eifel4 ,and here we find remarkable cases of breached cones1 or craters1 which will require some special description4 ,standing on the summit of the ,puy de ,dme1 and looking northwards or southwards1 the eye wanders over a tract formed of dome-shaped hills and of extinct crater-cones rising from a granitic platform4 ,but what is most peculiar in the scene is the ruptured condition of a large number of the cones with craters4 ,in such cases the wall of the crater has been broken down on one side1 and we observe that a stream of lava has been poured out through the breach and overflowed the plain below4 ,the cause of this breached form is sufficiently obvious4 ,in such cases there has been an explosion of ashes1 stones1 and scori from the volcanic throat1 by which a cone-shaped hill with a crater has been built up4 ,this has been followed by molten lava welling up through the throat1 and gradually filling the crater4 ,but1 as the lava is much more dense than the material of which the crater wall is composed1 the pressure of the lava outwards has become too great for the resistance of the wall1 which consequently has given way at its weakest part and1 a breach being formed1 the molten matter has flowed out in a stream which has inundated the country lying at the base of the cone4 ,in one instance mentioned by ,scrope1 the original upper limit of the lake of molten lava has left its mark in the form of a ring of slag on the inside of the breached crater4#d ,craterless ,domes4--,these differ essentially both in form and composition from those just described1 and have their typical representatives in the ,auvergne district1 though not without their analogues elsewhere1 as in the case of ,chimborazo1 in ,south ,america1 one of the loftiest volcanic mountains in the world4 ,illustration3 ,fig4 #b4--;,cotopaxi1 a volcano of the ,cordilleras of ,quito1 still active1 and covered by snow down to a level of #ad1hjj feet4 ,below this is a zone of naked rock1 succeeded by another of forest vegetation4 ,owing to the continuous extrusion of lava from the crater1 the cone is being gradually built up of fresh material1 and the crater is comparatively small in consequence4--7,a diagrammatic view after ,a4 von ,humboldt47 ,taking the ,puy de ,dme1 ,petit ,suchet1 ,cliersou1 ,grand ,sarcoui in ,auvergne1 and the ,mamelon in the ,isle of ,bourbon as illustrations1 we have in all these cases a group of volcanic hills1 dome-shaped and destitute of craters1 the summits being rounded or slightly flattened4 ,we also observe that the flanks rise more abruptly from their bases1 and contrast in outline with the graceful curve of the crater cones4 ,the dome-shaped volcanoes are generally composed of felsitic matter1 whether domite1 trachyte1 or andesite1 which has been extruded in a molten or viscous condition from some orifice or fissure in the earth's crust1 and being piled up and spreading outwards1 necessarily assumes such a form as that of a dome1 as has been shown by experiment on a small scale by ,dr4 ,e4 ,reyer1 of ,grtz4#e ,the contrast between the two forms 7those of the dome and the crater-cone7 is exemplified in the case of the ,grand ,sarcoui and its neighbours4 ,the former is composed of a species of trachyte2 the latter of ashes and fragmental matter which have been blown out of their respective vents of eruption into the air1 and piled up and around in a crateriform manner with sides of gradually diminishing slope outwards1 thus giving rise to the characteristic volcanic curve4 ,the two varieties here referred to1 contrasting in form1 composition1 and colour of material1 can be clearly recognised from the summit of the ,puy de ,dme1 which rises by a head and shoulders above its fellows1 and thus affords an advantageous standpoint from which to compare the various forms of this remarkable group of volcanic mountains4 ,cotopaxi 7,fig4 #b7 has been generally supposed to be a dome2 but ,whymper1 who ascended the mountain in #ahhj1 shows that it is a cone with a crater1 #b1cjj feet in largest diameter4 ,he determined the height to be #ai1fac feet above the ocean4 ,its real elevation above the sea is somewhat masked1 owing to the fact that it rises from the high plain of ,tapia1 which is itself #h1ijj feet above the sea surface4 ,the smaller peak on the right 7,fig4 #b7 is that of ,carihuairazo1 which reaches an elevation of over #af1jjj feet4 ,chimborazo1 in ,columbia1 province of ,quito1 is one of the loftiest of the chain of the ,andes1 and is situated in lat4 #a #cj' ,s41 long4 #gh #eh' ,w4 ,though not in a state of activity1 it is wholly composed of volcanic material1 and reaches an elevation of over #bj1jjj feet above the ocean2 its sides being covered by a sheet of permanent snow to a level of #b1fjj feet below the summit4#f ,seen from the shores of the ,pacific1 after the long rains of winter1 it presents a magnificent spectacle1 when the transparency of the air is increased1 and its enormous circular summit is seen projected upon the deep azure blue of the equatorial sky4 ,the great rarity of the air through which the tops of the ,andes are seen adds much to the splendour of the snow1 and aids the magical effect of its reflection4 ,chimborazo was ascended by ,humboldt and ,bonpland in #ahjb almost to the summit2 but at a height of #ai1cjj feet by barometrical measurement1 their further ascent was arrested by a wide chasm4 ,boussingault1 in company with ,colonel ,hall1 accomplished the ascent as far as the foot of the mass of columnar trachyte1 the upper surface of which1 covered by a dome of snow1 forms the summit of the mountain4 ,the whole mass of the mountain consists of volcanic rock1 varieties of andesite2 there is no trace of a crater1 nor of any fragmental materials1 such as are usually ejected from a volcanic vent of eruption4#g ,lava ,crater-,cones4--,a third form of volcanic mountain is that which has been built up by successive eruptions of basic lava1 such as basalt or dolerite1 when in a molten condition4 ,these are very rare1 and the slope of the sides depends on the amount of original viscosity4 ,where the lava is highly fused its slope will be slight1 but if in a viscous condition1 successive outpourings from the orifice1 unable to reach the base of the mountain1 will tend to form a cone with increasing slope upwards4 ,mauna ,loa and ,kilauea1 in the ,hawaiian ,group1 according to ,professor ,j4 ,d4 ,dana1 are basalt volcanoes in a normal state4 ,they have distinct craters1 and the material of which the mountain is formed is basalt or dolerite4 ,the volcano of ,rangitoto in ,auckland1 ,new ,zealand1 appears to belong to this class4 ,basalt is the most fusible of volcanic rocks1 owing to the augite and magnetite it contains1 so that it spreads out with a very slight slope when highly fused4 ,trachyte1 on the other hand1 is the least fusible owing to the presence of orthoclase felspar1 or quartz2 so that the volcanic domes formed of this material stand at a higher angle from the horizon than those of basaltic cones4 #a ,scenery and ,geology of ,scotland 7#ahfe71 p4 #bad4 #b ,humboldt says3 ,the form of isolated conical mountains1 as those of ,vesuvius1 ,etna1 the ,peak of ,teneriffe1 ,tunguagua1 and ,cotopaxi1 is certainly the shape most commonly observed in volcanoes all over the globe4--,views of ,nature1 translated by ,e4 ,c4 ,ott and ,h4 ,g4 ,bohn 7#ahej74 #c ,it is supposed that after the disastrous explosion of ,krakatoa in #ahhc the fine dust carried into the higher regions of the atmosphere was carried round almost the entire globe1 and remained suspended for a lengthened period1 as described in a future page4 #d ,another remarkable case is mentioned and figured by ,judd1 where one of the ,lipari ,isles1 composed of pumice and rising out of the ,mediterranean1 has been breached by a lava-stream of obsidian4--,loc4 cit41 p4 #abc4 #e ,reyer has produced such dome-shaped masses by forcing a quantity of plaster of ,paris in a pasty condition up through an orifice in a board2 referred to by ,judd1 loc4 cit41 p4 #abe4 #f ,whymper determined the height to be #bj1dih feet2 ,reiss and ,stbel make it #bj1gjc feet4 ,whymper thinks there may be a crater concealed beneath the dome of snow4--,travels amongst the ,great ,andes of the ,equator1 by ,edward ,whymper 7#ahib74 #g ,whymper states that there is a prevalent idea that ,cotopaxi and a volcano called ,sangai act as safety-valves to each other4 ,sangai reaches an elevation 7according to ,reiss and ,stbel7 of #ag1dfd feet1 and sends intermittent jets of steam high into the air1 spreading out into vast cumulus clouds1 which float away southwards1 and ultimately disappear4--,ibid41 p4 #gc4 ,,chapter ,,iii4 ,,lines ,,and ,,groups ,,of ,,active ,,volcanic ,,vents4 ,the globe is girdled by a chain of volcanic mountains in a state of greater or less activity1 which may perhaps be considered a girdle of safety for the whole world1 through which the masses of molten matter in a state of high pressure beneath the crust find a way of escape2 and thus the structure of the globe is preserved from even greater convulsions than those which from time to time take place at various points on its surface4 ,this girdle is partly terrestrial1 partly submarine2 and commencing at ,mount ,erebus1 near the ,antarctic ,pole1 ranging through ,south ,shetland ,isle1 ,cape ,horn1 the ,andes of ,south ,america1 the ,isthmus of ,panama1 then through ,central ,america and ,mexico1 and the ,rocky ,mountains to ,kamtschatka1 the ,aleutian ,islands1 the ,kuriles1 the ,japanese1 the ,philippines1 ,new ,guinea1 and ,new ,zealand1 reaches the ,antarctic ,circle by the ,balleny ,islands4 ,this girdle sends off branches at several points4 7,see ,map1 p4 #bc47 ,illustration3 ,fig4 #c4--,volcanic cone of ,orizaba 7,cittaltepeth71 in ,mexico1 now extinct2 the upper part snow-clad1 and at its base forest vegetation2 it reaches a height of #af1cjb ,parisian feet above the sea4--7,after ,a4 von ,humboldt47 7a47 ,the linear arrangement of active or dormant volcanic vents has been pointed out by ,humboldt1 ,von ,buch1 ,daubeny1 and other writers4 ,the great range of burning mountains of the ,andes of ,chili1 ,peru1 ,bolivia1 and ,mexico1 that of the ,aleutian ,islands1 of ,kamtschatka and the ,kurile ,islands1 extending southwards into the ,philippines1 and the branching range of the ,sunda ,islands are well-known examples4 ,that of the ,west ,indian ,islands1 ranging from ,grenada through ,st4 ,vincent1 ,st4 ,lucia1 ,martinique1 ,dominica1 ,guadeloupe1 ,montserrat1 ,nevis1 and ,st4 ,eustace1#a is also a remarkable example of the linear arrangement of volcanic mountains4 ,on tracing these ranges on a map of the world#b 7,map1 p4 #bc71 it will be observed that they are either strings of islands1 or lie in proximity to the ocean2 and hence the view was naturally entertained by some writers that oceanic water1 or at any rate that of a large lake or sea1 was a necessary agent in the production of volcanic eruptions4 ,this view seems to receive further corroboration from the fact that the interior portions of the continents and large islands such as ,australia are destitute of volcanoes in action1 with the remarkable exceptions of ,mounts ,kenia and ,kilimanjaro in ,central ,africa1 and a few others4 ,it is also very significant in this connection that many of the volcanoes now extinct1 or at least dormant1 both in ,europe and ,asia1 appear to have been in proximity to sheets of water during the period of activity4 ,thus the old volcanoes of the ,haurn1 east of the ,jordan1 appear to have been active at the period when the present ,jordan valley was filled with water to such an extent as to constitute a lake two hundred miles in length1 but which has now shrunk back to within the present limits of the ,dead ,sea4#c ,again1 at the period when the extinct volcanoes of ,central ,france were in active operation1 an extensive lake overspread the tract lying to the east of the granitic plateau on which the craters and domes are planted1 now constituting the rich and fertile plain of ,clermont4 ,illustration3 ,map ,of ,the ,world ,showing ,active ,and ,extinct ,volcanoes 7,large ,dots7 ,such instances are too significant to allow us to doubt that water in some form is very generally connected with volcanic operations2 but it does not follow that it was necessary to the original formation of volcanic vents1 whether linear or sporadic4 ,if this were so1 the extinct volcanoes of the ,british ,isles would still be active1 as they are close to the sea-margin1 and no volcano would now be active which is not near to some large sheet of water4 ,but ,jorullo1 one of the great active volcanoes of ,mexico1 lies no less than #abj miles from the ocean1 and ,cotopaxi1 in ,ecuador1 is nearly equally distant4 ,kilimanjaro1 #ah1hha feet high1 and ,kenia1 in the equatorial regions of ,central ,africa1 are about #aej miles from the ,victoria ,nyanza1 and a still greater distance from the ocean2 and ,mount ,demavend1 in ,persia1 which rises to an elevation of #ah1dfd feet near the southern shore of the ,caspian ,sea1 a volcanic mountain of the first magnitude1 is now extinct or dormant4#d ,such facts as these all tend to show that although water may be an accessory of volcanic eruptions1 it is not in all cases essential2 and we are obliged1 therefore1 to have recourse to some other theory of volcanic action differing from that which would attribute it to the access of water to highly heated or molten matter within the crust of the earth4 7b47 ,leopold von ,buch on ,rents and ,fissures in the ,earth's ,crust4--,the view of ,leopold von ,buch1 who considered that the great lines of volcanic mountains above referred to rise along the borders of rents1 or fissures1 in the earth's crust1 is one which is inherently probable1 and is in keeping with observation4 ,that the crust of the globe is to a remarkable extent fissured and torn in all directions is a phenomenon familiar to all field geologists4 ,such rents and fissures are often accompanied by displacement of the strata1 owing to which the crust has been vertically elevated on one side or lowered on the other1 and such displacements 7or faults7 sometimes amount to thousands of feet4 ,it is only occasionally1 however1 that such fractures are accompanied by the extrusion of molten matter2 and in the ,north of ,england and ,scotland dykes of igneous rock1 such as basalt1 which run across the country for many miles in nearly straight lines1 often cut across the faults1 and are only rarely coincident with them4 ,nevertheless1 it can scarcely be a question that the grand chain of volcanic mountains which stretches almost continuously along the ,andes of ,south ,america1 and northwards through ,mexico1 has been piled up along the line of a system of fissures in the fundamental rocks parallel to the coast1 though not actually coincident therewith4 7c47 ,the ,cordilleras of ,quito4--,the structure and arrangement of the ,cordilleras of ,quito1 for example1 are eminently suggestive of arrangement along lines of fissure4 ,as shown by ,alexander von ,humboldt1#e the volcanic mountains are disposed in two parallel chains1 which run side by side for a distance of over #ejj miles northwards into the ,state of ,columbia1 and enclose between them the high plains of ,quito and ,lacunga4 ,along the eastern chain are the great cones of ,el ,altar1 rising to an elevation of #af1chc feet above the ocean1 and having an enormous crater apparently dormant or extinct1 and covered with snow2 then ,cotopaxi 7,fig4 #b71 its sides covered with snow1 and sending forth from its crater several columns of smoke2 then ,guamani and ,cayambe 7#ai1jjj feet71 huge truncated cones apparently extinct2 these constitute the eastern chain of volcanic heights4 ,the western chain contains even loftier mountains4 ,here we find the gigantic ,chimborazo1 an extinct volcano whose summit is white with snow2 ,carihuairazo#f and ,illiniza1 a lofty pointed peak like the ,matterhorn2 ,corazon1 a snow-clad dome1 reaching a height of #ae1hga feet2 ,atacazo and ,pichincha1 the latter an extinct volcano reaching an elevation of #ae1ibj feet2 such is the western chain1 remarkable for its straightness1 the volcanic cones being planted in one grand procession from south to north4 ,this rectilinear arrangement of the western chain1 only a little less conspicuous in the eastern1 is very suggestive of a line of fracture in the crust beneath4 ,and when we contemplate the prodigious quantity of matter included within the limits of these colossal domes and their environments1 all of which has been extruded from the internal reservoirs1 we gain some idea of the manner in which the contracting crust disposes of the matter it can no longer contain4#g ,between the volcanoes of ,quito and those of ,peru there is an intervening space of fourteen degrees of latitude4 ,this is occupied by the ,andes1 regarding the structure of which we have not much information except that at this part of its course it is not volcanic4 ,but from ,arequipa in ,peru 7lat4 #af ,s471 an active volcano1 we find a new series of volcanic mountains continued southwards through ,tacora 7#ai1gdj feet71 then further south the more or less active vents of ,sajama 7#bb1iae feet71 ,coquina1 ,tutupaca1 ,calama1 ,atacama1 ,toconado1 and others1 forming an almost continuous range with that part of the desert of ,atacama pertaining to ,chili4 ,through this country we find the volcanic range appearing at intervals2 and still more to the southwards it is doubtless connected with the volcanoes of ,patagonia1 north of the ,magellan ,straits1 and of ,tierra del ,fuego4 ,mr4 ,david ,forbes considers that this great range of volcanic mountains1 lying nearly north and south1 corresponds to a line of fracture lying somewhat to the east of the range4#h 7d47 ,other ,volcanic ,chains4--,a similar statement in all probability applies to the systems of volcanic mountains of the ,aleutian ,isles1 ,kamtschatka1 the ,kuriles1 the ,philippines1 and ,sunda ,isles4 ,nor can it be reasonably doubted that the western ,american coast-line has to a great extent been determined1 or marked out1 by such lines of displacement2 for1 as ,darwin has shown1 the whole western coast of ,south ,america1 for a distance of between #bjjj and #cjjj miles south of the ,equator1 has undergone an upward movement in very recent times--that is1 within the period of living marine shells--during which period the volcanoes have been in activity4#i 7e47 ,the ,kurile ,islands4--,this chain may also be cited in evidence of volcanic action along fissure lines4 ,it connects the volcanoes of ,kamtschatka with those of ,japan1 and the linear arrangement is apparent4 ,in the former peninsula ,erman counted no fewer than thirteen active volcanic mountains rising to heights of #ab1jjj to #ae1jjj feet above the sea4#aj ,in the chain of the ,kuriles ,professor ,john ,milne counted fifty-two well-defined volcanoes1 of which nine1 perhaps more1 are certainly active4#aa ,they are not so high as those of ,kamtschatka2 but1 on the other hand1 they rise from very deep oceanic waters1 and have been probably built up from the sea bottom by successive eruptions of tuff1 lava1 and ash4 ,according to the view of ,professor ,milne1 the volcanoes of the ,kurile chain are fast becoming extinct4 7f47 ,volcanic ,groups4--,besides the volcanic vents arranged in lines1 of which we have treated above1 there are a large number1 both active and extinct1 which appear to be disposed in groups1 or sporadically distributed1 over various portions of the earth's surface4 ,i say appear to be1 because this sporadic distribution may really be resolvable 7at least in some cases7 into linear distribution for short distances4 ,thus the ,neapolitan ,group1 which might at first sight seem to be arranged round ,vesuvius as a centre1 really resolves itself into a line of active and extinct vents of eruption1 ranging across ,italy from the ,tyrrhenian ,sea to the ,adriatic1 through ,ischia1 ,procida1 ,monte ,nuovo and the ,phlegran ,fields1 ,vesuvius1 and ,mount ,vultur4#ab ,again1 the extinct volcanoes of ,central ,france1 which appear to form an isolated group1 indicate1 when viewed in detail1 a linear arrangement ranging from north to south4#ac ,another region over which extinct craters are distributed lies along the banks of the ,rhine1 above ,bonn and the ,moselle2 a fourth in ,hungary2 a fifth in ,asia ,minor and ,northern ,palestine2 and a sixth in ,central ,asia around ,lake ,balkash4 ,these are all continental1 and the linear distribution is not apparent4 #a ,for an interesting account of this range of volcanic islands see ,kingsley's ,at ,last4 ,the grandest volcanic peak is that of ,guadeloupe1 rising to a height of #ejjj feet above the ocean1 amidst a group of fourteen extinct craters4 ,but the most active vent of the range is the ,souffrire of ,st4 ,vincent4 ,in the eruption of #ahab this mountain sent forth clouds of pumice1 scori and ashes1 some of which were carried by an upper counter current to ,barbados1 one hundred miles to the eastward1 covering the surface with volcanic dust to a depth of several inches4 #b ,an excellent1 and perhaps the most recent1 map of this kind is that given by ,professor ,prestwich in his ,geology1 vol4 i4 p4 #baf4 ,one on a larger scale is that by ,keith ,johnston in his ,physical ,atlas4 #c ,memoir on the ,physical ,geology and ,geography of ,arabia ,petra1 ,palestine1 etc41 published for the ,committee of the ,palestine ,exploration ,fund 7#ahhf71 p4 #aac1 etc4 #d ,this mountain was ascended in #ahcg by ,mr4 ,taylor ,thomson1 who found the summit covered with sulphur1 and from a cone fumes at a high temperature issued forth1 but there was no eruption4--,journ4 ,roy4 ,geographical ,soc41 vol4 viii4 p4 #aji4 #e ,humboldt1 ,atlas der ,kleineren ,schriften 7#ahec74 #f ,ascended by ,whymper ,june #bi1 #ahhj4 ,he found the elevation to be #af1eae feet4 #g ,the arrangement of the volcanoes of ,peru and ,bolivia is also suggestive of a double line of fissure1 while those of ,chili suggest one single line4 ,the volcanoes of ,arequipa1 in the southern part of ,peru1 are dealt with by ,dr4 ,f4 ,h4 ,hatch1 in his inaugural dissertation1 ,ueber die ,gesteine der ,vulcan-,gruppe von ,arequipa 7,wien1 #ahhf74 ,the volcanoes rise to great elevations1 having their summits capped by snow4 ,the volcano of ,charchani1 lying to the north of ,arequipa1 reaches an elevation of #ah1chb ,parisian feet4 ,that of ,pichupichu reaches a height of #ag1cee ,par4 feet4 ,the central cone of ,misti has been variously estimated to range from #ag1bdj to #ai1jjj ,par4 feet4 ,the rocks of which the mountains are composed consist of varieties of andesite4 #h ,d4 ,forbes1 ,on the ,geology of ,bolivia and ,southern ,peru1 ,quarterly ,journal of the ,geological ,society1 vol4 xvii4 p4 #bb 7#ahfa74 #i ,darwin1 ,structure and ,distribution of ,coral ,reefs1 second edition1 p4 #ahf4 #aj ,erman1 ,reise um die ,welt4 #aa ,milne1 ,cruise amongst the ,kurile ,islands1 ,geol4 ,mag41 ,new ,ser4 7,august #ahgi74 #ab ,see ,daubeny1 ,volcanoes1 ,map ,i4 #ac ,sir ,a4 ,geikie has connected as a line of volcanic vents those of ,sicily1 ,italy1 ,central ,france1 the ,n4 ,e4 of ,ireland1 the ,inner ,hebrides and ,iceland1 of which the central vents are extinct or dormant1 the extremities active4 ,,chapter ,,iv4 ,,mid-,,ocean ,,volcanic ,,islands4 ,oceanic ,islands4--,by far the most extensive regions with sporadically distributed volcanic vents1 both active and extinct1 are those which are overspread by the waters of the ocean1 where the vents emerge in the form of islands4 ,these are to be found in all the great oceans1 the ,atlantic1 the ,pacific1 and the ,indian2 but are especially numerous over the central ,pacific region4 ,as ,kotzebue and subsequently ,darwin have pointed out1 all the islands of the ,pacific are either coral-reefs or of volcanic origin2 and many of these rise from great depths2 that is to say1 from depths of #ajjj to #bjjj fathoms4 ,it is unnecessary here to attempt to enumerate all these islands which rise in solitary grandeur from the surface of the ocean1 and are the scenes of volcanic operations2 a few may1 however1 be enumerated4 ,illustration3 ,fig4 #d4--,the ,peak of ,teneriffe 7,pic de ,teyde7 as seen from the ocean4--7,from a photograph47 7a47 ,iceland4--,in the ,atlantic1 ,iceland first claims notice1 owing to the magnitude and number of its active vents and the variety of the accompanying phenomena1 especially the geysers4 ,as ,lyell has observed1#a with the exception of ,etna and ,vesuvius1 the most complete chronological records of a series of eruptions in existence are those of ,iceland1 which come down from the ninth century of our era1 and which go to show that since the twelfth century there has never been an interval of more than forty years without either an eruption or a great earthquake4 ,so intense is the volcanic energy in this island that some of the eruptions of ,hecla have lasted six years without cessation4 ,earthquakes have often shaken the whole island at once1 causing great changes in the interior1 such as the sinking down of hills1 the rending of mountains1 the desertion by rivers of their channels1 and the appearance of new lakes4 ,new islands have often been thrown up near the coast1 while others have disappeared4 ,in the intervals between the eruptions1 innumerable hot springs afford vent to the subterranean heat1 and solfataras discharge copious streams of inflammable matter4 ,the volcanoes in different parts of the island are observed1 like those of the ,phlegran ,fields1 to be in activity by turns1 one vent serving for a time as a safety-valve for the others4 ,the most memorable eruption of recent years was that of ,skaptr ,jokul in #aghc1 when a new island was thrown up1 and two torrents of lava issued forth1 one #de and the other #ej miles in length1 and which1 according to the estimate of ,professor ,bischoff1 contained matter surpassing in magnitude the bulk of ,mont ,blanc4 ,one of these streams filled up a large lake1 and1 entering the channel of the ,skapt1 completely dried up the river4 ,the volcanoes of ,iceland may be considered as safety-valves to the region in which lie the ,british ,isles4 7b47 ,the ,azores1 ,canary1 and ,cape de ,verde ,groups4--,this group of volcanic isles rises from deep ,atlantic waters north of the ,equator1 and the vents of eruption are partially active1 partially dormant1 or extinct4 ,it must be supposed1 however1 that at a former period volcanic action was vastly more energetic than at present2 for1 except at the ,grand ,canary1 ,gomera1 ,forta ,ventura1 and ,lancerote1 where various non-volcanic rocks are found1 these islands appear to have been built up from their foundations of eruptive materials4 ,the highest point in the ,azores is the ,peak of ,pico1 which rises to a height of #gjaf feet above the ocean4 ,but this great elevation is surpassed by that of the ,peak of ,teneriffe 7or ,pic de ,teyde7 in the ,canaries1 which attains to an elevation of #ab1bbe feet1 as determined by ,professor ,piazzi ,smyth4#b ,this great volcanic cone1 rising from the ocean1 its summit shrouded in snow1 and often protruding above the clouds1 must be an object of uncommon beauty and interest when seen from the deck of a ship4 7,fig4 #d47 ,the central cone1 formed of trachyte1 pumice1 obsidian1 and ashes1 rises out of a vast caldron of older basaltic rocks with precipitous inner walls--much as the cone of ,vesuvius rises from within the partially encircling walls of ,somma4 7,fig4 #e47 ,from the summit issue forth sulphurous vapours1 but no flame4 ,piazzi ,smyth1 who during a prolonged visit to this mountain in #ahef made a careful survey of its form and structure1 shows that the great cone is surrounded by an outer ring of basalt enclosing two foci of eruption1 the lavas from which have broken through the ring of the outer crater on the western side1 and have poured down the mountain4 ,at the top of the peak its once active crater is filled up1 and we find a convex surface 7,the ,plain of ,rambleta7 surmounted towards its eastern end by a diminutive cone1 #ejj feet high1 called ,humboldt's ,ash ,cone4 ,the slope of the great cone of ,teneriffe ranges from #bh to #ch2 and below a level of #gjjj feet the general slope of the whole mountain down to the water's edge varies from #aj to #ab from the horizontal4 ,the great cone is penetrated by numerous basaltic dykes4 ,the ,cape de ,verde ,islands1 which contain beds of limestone along with volcanic matter1 possess in the island of ,fuego an active volcano1 rising to a height of #gjjj feet above the surface of the ocean4 ,the central cone1 like that of ,teneriffe1 rises from within an outer crater1 formed of basalt alternating with beds of agglomerate1 and traversed by numerous dykes of lava4 ,this has been broken down on one side like that of ,somma2 and over its flanks are scattered numerous cones of scori1 the most recent dating from the years #aghe and #agii4c ,illustration3 ,fig4 #e4--,view of the summit of the ,peak of ,teneriffe 7#ab1bbe feet7 and of the secondary crater1 or outer ring of basaltic sheets which surrounds its base2 seen from the east4--7,after ,leopold von ,buch47 ,the volcanoes of ,lancerote have a remarkably linear arrangement from west to east across the island4 ,they are not yet extinct2 for an eruption in #agcj destroyed a large number of villages1 and covered with lava the most fertile tracts in the island1 which at the time of ,leopold von ,buch's visit lay waste and destitute of herbage4#d ,in the island of ,palma there is one large central crater1 the ,caldera de ,palma1 three leagues in diameter1 the walls of which conform closely to the margin of the coast4 ,von ,buch calls this crater une merveille de la nature1 for it distinguishes this isle from all the others1 and renders it one of the most interesting and remarkable amongst the volcanic islands of the ocean4 ,the outer walls are formed of basaltic sheets1 and towards the south this great natural theatre is connected with the ocean by a long straight valley1 called the ,barranco de los ,dolores1 along whose sides the structure of the mountain is deeply laid open to view4 ,the outer flanks of the crater are furrowed by a great number of smaller barrancos radiating outward from the rim of the caldera4 ,von ,buch regards the barrancos as having been formed during the upheaval of the island1 according to his theory of the formation of such mountains 7the elevation-theory72 but unfortunately for his views1 these ravines widen outwards from the centre1 or at least do not become narrower in that direction1 as would be the case were the elevation-theory sound4 ,the maps which accompany ,von ,buch's work are remarkably good1 and were partly constructed by himself4 7c47 ,volcanic ,islands in the ,atlantic south of the ,equator4--,the island of ,ascension1 formed entirely of volcanic matter1 rises from a depth of #bjjj fathoms in the very centre of the ,atlantic4 ,as described by ,darwin1 the central and more elevated portions are formed of trachytic matter1 with obsidian and laminated ash beds4 ,amongst these are found ejected masses of unchanged granite1 fragments of which have been torn from the central pipe during periods of activity1 and would seem to indicate a granitic floor1 or at least an original floor upon which more recent deposits may have been superimposed4 ,in ,st4 ,helena we seem1 according to ,daubeny1 to have the mere wreck of one great crater1 no one stream of lava being traceable to its source1 while dykes of lava are scattered in profusion throughout the whole substance of the basaltic masses which compose the island4 ,tristan da ,cunha1 in the centre of the ,south ,atlantic1 rises abruptly from a depth of #ab1aej feet1 at a distance of #aejj miles from any land2 and one of its summits reaches an elevation of #gjjj feet1 being a truncated cone composed of alternating strata of tuff and augitic lava1 surrounding a crater in which is a lake of pure water4 ,the volcano is extinct or dormant4 ,were the waters of the ocean to be drawn off1 these volcanic islands would appear like stupendous conical mountains1 far loftier1 and with sides more precipitous1 than any to be found on our continental lands1 all of which rise from platforms of considerable elevation4 ,the enormous pressure of the water on their sides enables these mid-oceanic islands to stand with slopes varying from the perpendicular to a smaller extent than if they were sub-aerial2 and it is on this account that we find them rising with such extraordinary abruptness from the vasty deep4 7d47 ,volcanic ,islands of the ,pacific4--,the volcanic islands of this great ocean are scattered over a wide tract on both sides of the equator4 ,those to the north of this line include the ,sandwich ,islands1 the ,mariana or ,ladrone ,islands1 ,south ,island1 and ,bonin ,sima2 south of the equator1 the ,galapagos1 ,new ,britain1 ,salomon1 ,santa ,cruz1 ,new ,hebrides1 the ,friendly and ,society ,isles4 ,while the coral reefs and islands of the ,pacific may be recognised by their slight elevation above the surface of the waters1 those of volcanic origin and containing active or extinct craters of eruption generally rise into lofty elevations1 so that the two kinds are called the ,low ,islands and ,high ,islands respectively4 ,amongst the group are trachytic domes such as the ,mountain of ,tobreonu in the ,society ,islands1 rising to a height probably not inferior to that of ,etna1 with extremely steep sides1 and holding a lake on its summit4#e ,the linear arrangement of some of the volcanic islands of the ,pacific is illustrated by those of the ,tonga1 or ,friendly1 ,group1 lying to the north of ,new ,zealand4 ,they consist of three divisions--7#a7 the volcanic2 7#b7 those formed of stratified volcanic tuff1 sometimes entirely or partially covered by coralline limestone2 and 7#c7 those which are purely coralline4 ,the first form a chain of lofty cones and craters1 lying in a ,e4,n4,e4 and ,w4,s4,w4 direction1 and rising from depths of over #ajjj fathoms4 ,mr4 ,j4 ,j4 ,lister1 who has described the physical characters of these islands1 has shown very clearly that they lie along a line--probably that of a great fissure--stretching from the volcanic island of ,amargura on the north 7lat4 #ah ,s471 through ,lette1 ,metis1 ,kao 7#cjcj feet71 ,tofua1 ,falcon1 ,honga ,tonga1 and the ,kermadec ,group into the ,new ,zealand chain on the south4 ,some of these volcanoes are in a state of intermittent activity1 as in the case of ,tofua 7lat4 #bj #cj' ,s471 ,metis ,island1 and ,amargura2 the others are dormant or extinct4 ,the whole group appears to have been elevated at a recent period1 as some of the beds of coral have been raised #abgb feet and upward above the sea-level1 as in the case of ,eua ,island4#f ,the greater number of the ,pacific volcanoes appear to be basaltic2 such as those of the ,hawaiian ,group1 which have been so fully described by ,professor ,j4 ,d4 ,dana4#g ,here fifteen volcanoes of the first class have been in brilliant action2 all of which1 except three1 are now extinct1 and these are in ,hawaii the largest and most eastern of the group4 ,this island contains five volcanic mountains1 of which ,kea1 #ac1hje feet1 is the highest2 next to that1 ,loa1 #ac1fge feet2 after these1 ,hualalai1 rising #hbgc feet2 ,kilauea1 #daeh feet2 and ,kohala1 #eeje feet above the sea2 this last is largely buried beneath the lavas of ,mauna ,kea4 ,the group contains a double line of volcanoes1 one lying to the north and west of the other2 and as the highest of the ,hawaiian ,group rises from a depth in the ocean of over #bjjj fathoms1 the total elevation of this mountain from its base on the bed of the ocean is not far from #bf1jjj feet1 an elevation about that of the ,himalayas4 ,mauna ,kea has long been extinct1 ,hualalai has been dormant since #ahja2 but ,mauna ,loa is terribly active1 there having been several eruptions1 accompanied by earthquakes1 within recent years1 the most memorable being those of #aheb and #ahfh4 ,in the former case the lava rose from the deep crater into a lofty mountain1 as described by ,mr4 ,coan1#h and then flowed away eastward for a distance of twenty miles4 ,the interior of the crater consists of a vast caldron1 surrounded by a precipice #bjj to #djj feet in depth1 with a circumference of about fifteen miles1 and containing within it a second crater1 bounded by a black ledge with a steep wall of basalt--a crater within a crater2 and from the floor of the inner crater1 formed of molten basalt1 in a seething and boiling state1 arise a large number of small cones and pyramids of lava1 some emitting columns of grey smoke1 others brilliant flames and streams of molten lava1 presenting a wonderful spectacle1 the effect of which is heightened by the constant roaring of the vast furnaces below4#i #a ,principles of ,geology1 #aath edition1 vol4 ii4 p4 #dh4 #b ,smyth1 ,report on the ,teneriffe ,astronomical ,experiment of #ahef4 ,humboldt makes the elevation #ab1jij feet4 ,a beautiful model of the ,peak was constructed by ,mr4 ,j4 ,nasmyth from ,piazzi ,smyth's plans1 of which photographs are given by the latter4 #c ,daubeny1 loc4 cit41 p4 #dfj4 #d ,iles ,canaries1 p4 #cg4 #e ,daubeny1 loc4 cit41 p4 #dbf4 #f ,lister1 ,notes on the ,geology of the ,tonga ,islands1 ,quart4 ,jour4 ,geol4 ,soc41 ,no4 #ahh1 p4 #eij 7#ahia74 #g ,dana1 ,characteristics of ,volcanoes1 with ,contributions of ,facts and ,principles from the ,hawaiian ,islands4 ,london1 #ahij4--;,also1 ,geology of the ,american ,exploring ,expedition--,volcanoes of the ,sandwich ,islands4 #h ,coan1 ,amer4 ,jour4 of ,science1 #ahec4 #i ,w4 ,ellis1 the missionary1 has given a vivid description of this volcano in his ,tour of ,hawaii4 ,london1 #ahbf4--,plans of the crater will be found in ,professor ,dana's work above quoted4 ,,part ,,ii4 ,,european ,,volcanoes4 ,,chapter ,i4 ,,vesuvius4 ,having now dealt in a necessarily cursory manner with volcanoes of distant parts of the globe1 we may proceed to the consideration of the group of active volcanoes which still survive in ,europe1 as they possess a special interest1 not only from their proximity and facility of access1 at least to residents in ,europe and the ,british ,isles1 but from their historic incidents2 and in this respect ,vesuvius1 though not by any means the largest of the group1 stands the first1 and demands more special notice4 ,the whole group rises from the shores of the ,mediterranean1 and consists of ,vesuvius1 ,etna1 ,stromboli1 one of the ,lipari ,islands1 and ,vulcano1 a mountain which has given the name to all mountains of similar origin with itself4#a ,along with these are innumerable cones and craters of extinct or dormant volcanoes1 of which a large number have been thrown out on the flanks of ,etna4 7a47 ,prehistoric ,ideas regarding the ,nature of this ,mountain4--,down to the commencement of the ,christian era this mountain had given no ostensible indication that it contained within itself a powerful focus of volcanic energy4 ,true1 that some vague tradition that the mountain once gave forth fire hovered around its borders2 and several ancient writers1 amongst them ,diodorus ,siculus and ,strabo1 inferred from the appearances of the higher parts of the mountain and the character of the rocks1 which were cindery and as if eaten by fire1 that the country was once in a burning state1 being full of fiery abysses1 though now extinct from want of fuel4 ,seneca 7,b4,c4 #a to ,a4,d4 #fd7 had detected the true character of ,vesuvius1 as having been a channel for the internal fire1 but not its food2 nevertheless1 at this period the flanks of the mountain were covered by fields and vineyards1 while the summit1 partially enclosed with precipitous walls of the long extinct volcano1 ,somma1 was formed of slaggy and scoriaceous material1 with probably a covering of scrub4 ,here it was that the gladiator ,spartacus 7,b4,c4 #gb71 stung by the intolerable evils of the ,roman ,government1 retreated to the very summit of the mountain with some trusty followers4 ,clodius the ,prtor1 according to the narration of ,plutarch1 with a party of three thousand men1 was sent against them1 and besieged them in a mountain 7meaning ,vesuvius or ,somma7 having but one narrow and difficult passage1 which ,clodius kept guarded2 all the rest was encompassed with broken and slippery precipices1 but upon the top grew a great many wild vines2 the besieged cut down as many as they had need of1 and twisted them into ladders long enough to reach from thence to the bottom1 by which1 without any danger1 all got down except one1 who stayed behind to throw them their arms1 after which he saved himself with the rest4#b ,on the top must 7as ,professor ,phillips observes7 be interpreted the summit of the exterior slope or crater edge1 which would appear from the narrative to have broken down on one side1 affording an entrance and mode of egress by which ,spartacus fell upon1 and surprised1 the negligent ,clodius ,glabrus4 ,illustration3 ,fig4 #f4--,probable aspect of ,vesuvius as it appeared at the beginning of the ,christian era2 seen from the ,bay of ,naples4 ,in fancied security1 villas1 temples1 and cities had been erected on the slopes of the mountain4 ,herculaneum1 ,pompeii1 and ,stabi1 the abodes of art1 luxury1 and vice1 had sprung up in happy ignorance that they stood on a volcano1 and that their prosperity was to have a sudden and disastrous close4#c 7b47 ,premonitory ,earthquake ,shocks4--,the first monitions of the impending catastrophe occurred in the #fcrd year after ,christ1 when the whole ,campagna was shaken by an earthquake1 which did much damage to the towns and villas surrounding the mountain even beyond ,naples4 ,this was followed by other shocks2 and in ,pompeii the temple of ,isis was so much damaged as to require reconstruction1 which was undertaken and carried out by a citizen at his own expense4#d ,these earthquake shakings continued for sixteen years4 ,at length1 on the night of ,august #bdth1 ,a4,d4 #gi1 they became so violent that the whole region seemed to reel and totter1 and all things appeared to be threatened with destruction4 ,the next day1 about one in the afternoon1 there was seen to rise in the direction of ,vesuvius a dense cloud1 which1 after ascending from the summit of the mountain into the air for a certain height in one narrow1 vertical trunk1 spread itself out laterally in such a form that the upper part might be compared to the cluster of branches1 and the lower to the stem of the pine which forms so common a feature in the ,italian landscape4#e 7c47 ,pliny's ,letters to ,tacitus4--,for an account of what followed we are indebted to the admirable letters of the younger ,pliny1 addressed to the historian ,tacitus1 recounting the events which caused1 or accompanied1 the death of his uncle1 the elder ,pliny1 who at the time of this first eruption of ,vesuvius was in command of the ,roman fleet at the entrance to the ,bay of ,naples4 ,these letters1 which are models of style and of accurate description1 are too long to be inserted here2 but he recounts how the dense cloud which hung over the mountain spread over the whole surrounding region1 sometimes illuminated by flashes of light more vivid than lightning2 how showers of cinders1 stones1 and ashes fell in such quantity that his uncle had to flee from ,stabi1 and that even at so great a distance as ,misenum they encumbered the surface of the ground2 how the ground heaved and the bed of the sea was upraised2 how the cloud descended on ,misenum1 and even the island of ,capre was concealed from view2 and finally1 how1 urged by a friend who had arrived from ,spain1 he1 with filial affection1 supported the steps of his mother in flying from the city of destruction4 ,such being the condition of the atmosphere and the effects of the eruption at a point so distant as ,cape ,misenum1 some sixteen geographical miles from the focus of eruption1 it is only to be expected that places not half the distance1 such as ,herculaneum1 ,pompeii1 and even ,stabi1 with many villages and dwellings1 should have shared a worse fate4 ,the first of these cities1 situated on the coast of the ,bay of ,naples1 appears to have been overwhelmed by volcanic mud2 ,pompeii was buried in ashes and lapilli1 and ,stabi probably shared a similar fate4#f 7d47 ,appearance of the ,mountain at the ,commencement of the ,christian ,era4--,at the time of the first recorded eruption ,vesuvius appears to have consisted of only a single cone with a crater1 now known as ,monte di ,somma1 the central cone of eruption which now rises from within this outer ruptured casing not having been formed4 7,fig4 #f47 ,the first effect of the eruption of the year #gi was to blow out the solidified covering of slag and scori forming the floor of the caldron4 ,doubtless at the close of the eruption a cone of fragmental matter and lava of some slight elevation was built up1 and1 if so1 was subsequently destroyed2 for1 as we shall presently see by the testimony of the ,abate ,guilio ,cesare ,braccini1 who examined the mountain not long before the great eruption of ,a4,d4 #afca1 there was no central cone to the mountain at that time2 and the mountain had assumed pretty much the appearance it had at the time that ,spartacus took refuge within the walls of the great crater4 7e47 ,destruction of ,pompeii4--,pompeii was overwhelmed with dry ashes and lapilli4 ,sir ,w4 ,hamilton found some of the stones to weigh eight pounds4 ,at the time of the author's visit1 early in ,april #ahgb1 the excavations had laid open a section about ten feet deep1 chiefly composed of alternating layers of small pumice stones 7lapilli7 and volcanic dust4 ,it was during the sinking of a well in #agac upon the theatre containing the statues of ,hercules and ,cleopatra that the existence of the ancient city was accidentally discovered4 7f47 ,more recent eruptions4--,since the first recorded eruption in ,a4,d4 #gi down to the present day1 ,vesuvius has been the scene of numerous intermittent eruptions1 of which some have been recorded2 but many1 doubtless1 are forgotten4 ,in ,a4,d4 #bjc1 during the reign of ,severus1 an eruption of extraordinary violence took place1 which is related by ,dion ,cassius1 from whose narrative we may gather that at this time there was only one large crater1 and that the central cone of ,vesuvius had not as yet been upraised4 ,in ,a4,d4 #dgb an eruption occurred of such magnitude as to cover all ,europe with fine dust1 and spread alarm even at ,constantinople4 7g47 ,eruption of #afca4--;,in ,december #afca occurred the great convulsion whose memorials are written widely on the western face of ,vesuvius in ruined villages4 ,this eruption left layers of ashes over hundreds of miles of country1 or heaps of mud swept down by hot water floods from the crater2 the crater itself having been dissipated in the convulsion4 ,braccini1 who examined the mountain not long before this eruption1 found apparently no cone 7or mount7 like that of the modern ,vesuvius4 ,he states that the crater was five miles in circumference1 about a thousand paces deep 7or in sloping descent71 and its sides covered with forest trees and brushwood1 while at the bottom there was a plain on which cattle grazed4#g ,it would seem that the mountain had at this time enjoyed a long interval of rest1 and that it had reverted to very much the same state in which it was at the period of the first eruption1 when the flanks were peopled by inhabitants living in fancied security4 ,but six months of violent earthquakes1 which grew more violent towards the close of #afca1 heralded the eruption which took place in ,december1 accompanied by terrific noises from within the interior of the mountain4 ,the inhabitants of the coast were thus warned of the approaching danger1 and had several days to arrange for their safety2 but in the end1 a great part of ,torre del ,greco was destroyed1 and a like fate overtook ,resina and ,granatello1 with a loss of life reported at #ah1jjj persons4 ,during the eruption clouds condensed into tempests of rain1 and hot water from the mountain1 forming deluges of mud1 swept down the sides1 and reached even to ,nola and the ,apennines4 ,nor was the sea unmoved4 ,it retired during the violent earthquakes1 and then returned full thirty paces beyond its former limits4 ,not indeed until near the close of the seventeenth century is there any evidence that the central cone of ,vesuvius was in existence2 but in ,october #afhe an eruption occurred which is recorded by ,sorrentino1 during which was erected a new mountain within1 and higher than the old one1 and visible from ,naples1 a statement evidently referable to the existing cone--so that it is little more than two centuries since this famous volcanic mountain assumed its present form4 7h47 ,eruptions between the years #aejj and #ahjj4--,since ,a4,d4 #aejj there have been fifty-six recorded eruptions of ,vesuvius2 one of these in #agfg was of terrific violence and destructiveness1 and is represented by ,sir ,william ,hamilton in views taken both before and during the eruption4 ,a pen-and-ink drawing of the appearance of the crater before the eruption is here reproduced from ,hamilton's picture1 from which it will be seen that the central crater contained within itself a second crater-cone1 from whence steam1 lava1 and stones were being erupted 7,fig4 #g74 ,thus it will be seen that ,vesuvius at this epoch consisted of three crater-cones within each other4 ,the first1 ,monte di ,somma2 the second1 the cone of ,vesuvius2 and the third1 the little crater-cone within the second4 ,during this eruption1 vast lava-sheets invaded the fields and vineyards on the flanks of the mountain4 ,a vivid account of this eruption1 as witnessed by ,padre ,torre1 is given by ,professor ,phillips4#h ,we shall pass over others without further reference until we come down to our own times1 in which ,vesuvius has resumed its old character1 and in one grand exhibition of volcanic energy1 which took place in #ahgb1 has evinced to the world that it still contains within its deep-seated laboratory all the elements of destructive force which it exhibited at the commencement of our era4 ,illustration3 ,fig4 #g4--,view of the crater of ,vesuvius before the eruption of #agfg1 showing an interior crater-cone rising from the centre of the exterior crater4--7,after ,sir ,w4 ,hamilton47 7i47 ,structure of the ,neapolitan ,campagna4--,but before giving a description of this terrific outburst of volcanic energy1 it may be desirable to give some account of the physical position and structure of this mountain1 by which the phenomena of the eruption will be better understood4 ,vesuvius and the ,neapolitan ,campagna are formed of volcanic materials bounded on the west by the ,gulf of ,naples1 and on the east and south by ranges of ,jurassic limestone1 a prolongation of the ,apennines1 which send out a spur bounding the bay on the south1 and forming the promontory of ,sorrento4 ,the little island of ,capri is also formed of limestone1 and is dissevered from the promontory by a narrow channel4 ,the northern side of the bay is1 however1 formed of volcanic materials2 it includes the ,phlegran ,fields 7,campi ,phlegri71 and terminates in the promontory of ,miseno4 ,lying in the same direction are the islands of ,procida and ,ischia1 also volcanic4 ,hence it will be seen that the two horns of the bay are formed of entirely different materials1 that of ,miseno on the north being volcanic1 that of ,sorrento on the south being composed of ,jurassic limestone1 of an age vastly more ancient than the volcanic rocks on the opposite shore4 7,map1 p4 #eb47 ,the general composition of the ,neapolitan ,campagna1 from which the mountain rises1 has been revealed by means of the ,artesian well sunk to a depth of about #ejj metres 7#afdj feet7 at the ,royal ,palace of ,naples1 and may be generalised as follows3-- ,recent beds of volcanic tuff 7#a7 ,from surface to depth of with marine shells1 and containing #gae feet fragments of trachytic lava1 etc4 7,volcanic ,beds74 ,bituminous sands and marls 7#b7 ,from #gae to #adbj with marine shells of recent species787 7,pre-,volcanic ,beds74 7#c7 ,from #adbj to #aegd ,,eocene ,,beds4 ,micaceous sandstone and marl 7,macigno74 7#d7 ,from #aegd to bottom ,,jurassic ,,beds4 ,apennine ,limestone4 ,illustration3 ,fig4 #h4--,map of the district bordering the ,bay of ,naples1 with the islands of ,capri1 ,ischia1 and ,procida4 ,from the above section1 for which we are indebted to ,mr4 ,johnston-,lavis1 the most recent writer on ,vesuvius1 it would appear that the first volcanic explosions by which the mountain was ultimately to be built up took place after the deposition of the sands and marls 7,no4 #b71 while the whole ,campagna was submerged under the waters of the ,mediterranean4 ,by the accumulation of the stratified tuff 7,no4 #a71 the sea-bed was gradually filled up during a period of volcanic activity1 and afterwards elevated into dry land4#i ,illustration3 ,fig4 #i4--,view of ,vesuvius from the ,harbour of ,naples at the commencement of the eruption of #ahgb4--7;,from a sketch by the author47 7j47 ,present ,form and ,structure of ,vesuvius and ,somma4--,the outer cone of ,vesuvius1 or ,monte di ,somma1 rises from a circular platform by a moderately gentle ascent1 and along the north and east terminates in a craggy crest1 with a precipitous cliff descending into the ,atria del ,cavallo1 forming the wall of the ancient crater throughout half its circumference2 this wall is formed of scori1 ashes1 and lapilli1 and is traversed by numerous dykes of lava4 ,along the west and south this old crater has been broken down2 but near the centre there remains a round-backed ridge of similar materials1 once doubtless a part of the original crater of ,somma1 rising above the slopes of lava on either hand4 ,on this has been erected the ,royal ,observatory1 under the superintendence of ,professor ,luigi ,palmieri1 where continuous observations are being made1 by means of delicate seismometers1 of the earth-tremors which precede or accompany eruptions2 for it is only justice to say that ,vesuvius gives fair warning of impending mischief1 and the instruments are quick to notify any premonitory symptoms of a coming catastrophe4 ,the elevation of the ,observatory is #bjhj feet above the sea4 ,on either side of the ,observatory ridge are wide channels filled to a certain height with lavas of the nineteenth and preceding centuries1 the most recent presenting an aspect which can only be compared to a confused multitude of black serpents and pachyderms writhing and interlocked in some frightful death-struggle4 ,some of this lava1 ten years old1 as we cross its rugged and black surface presents gaping fissures1 showing the mass to be red-hot a few feet from the surface1 so slow is the process of cooling4 ,these lava-streams--some of them reaching to the sea-coast--have issued forth from the ,atria at successive periods of eruption4 ,from the midst of the ,atria rises the central cone1 formed of cinders1 scori1 and lava-streams1 and fissured along lines radiating from the axis4 ,this cone is very steep1 the angle being about #dj-de from the horizontal1 and is formed of loose cindery matter which gives way at every step1 and is rather difficult to climb4 ,but on reaching the summit we look down into the crater1 displaying a scene of ever-varying characters1 rather oval in form1 and about #aajj yards in diameter4 ,from the map of ,professor ,guiscardi1 published in #ahee1 there are seen two minor craters within the central one1 formed in #ahej1 and an outflow of lava from the ,n4,w4 down the cone4 ,at the time of the author's visit the crater was giving indications1 by the great quantity of sulphurous gas and vapour rising from its surface1 and small jets of molten lava beginning to flow down the outer side1 of the grand outburst of internal forces which was presently to follow4 7k47 ,eruption of #ahgb4--,the grand eruption of #ahgb1 of which a detailed account is given by ,professor ,palmieri1#aj commenced with a slight discharge of incandescent projectiles from the crater2 and on the #acth ,january an aperture appeared on the upper edge of the cone from which at first a little lava issued forth1 followed by the uprising of a cone which threw out projectiles accompanied by smoke1 whilst the central crater continued to detonate more loudly and frequently4 ,this little cone ultimately increased in size1 until in ,april it filled the whole crater and rose four or five metres above the brim4 ,at this time abundant lavas poured down from the base of the cone into the ,atria del ,cavallo1 thence turned into the ,fossa della ,vetraria in the direction of the ,observatory and towards the ,crocella1 where they accumulated to such an extent as to cover the hillside for a distance of about #cjj metres2 then turning below the ,canteroni1 formed a hillock without spreading much farther4 ,in ,october another small crater was formed by the falling in of the lava1 which after a few days gave vent to smoke and several jets of lava2 and towards the end of ,october the detonations increased1 the smoke from the central crater issued forth more densely mixed with ashes1 and the seismographical apparatus was much disturbed4 ,on the #crd and #dth ,november copious and splendid lava-streams coursed down the principal cone on its western side1 but were soon exhausted2 and in the beginning of #ahgb the little cone1 regaining vigour1 began to discharge lava from the summit instead of the base as heretofore4 ,in the month of ,march #ahgc1 with the full moon1 the cone opened on the north-west side--the cleavage being indicated by a line of fumaroles--and lava issued from the base and poured down into the ,atria as far as the precipices of ,monte di ,somma4 ,on the #bcrd ,april 7another full moon7 the activity of the craters increased1 and on the evening of the #bdth splendid lava-streams descended the cone in various directions1 attracting on the same night the visits of a great many strangers4 ,a lamentable event followed on the #bfth4 ,a party of visitors1 accompanied by inexperienced guides1 and contrary to the advice of ,professor ,palmieri1 insisted on ascending to the place from which the lava issued4 ,at half-past three on the morning of the #bfth they were in the ,atria del ,cavallo1 when the ,vesuvian cone was rent in a north-west direction and a copious torrent of lava issued forth4 ,two large craters formed at the summit of the mountain1 discharging incandescent projectiles and ashes4 ,a cloud of smoke enveloped the unhappy visitors1 who were under a hail-storm of burning projectiles4 ,eight were buried beneath it1 or in the lava1 while eleven were grievously injured4#aa ,the lava-stream1 flowing over that of #ahga in the ,atria1 divided into two branches1 the smaller one flowing towards ,resina1 but stopping before reaching the town2 the larger precipitated itself into the ,fossa della ,vetraria1 occupying the whole width of #hjj metres1 and traversing the entire length of #acjj metres in three hours4 ,it dashed into the ,fossa di ,farone1 and reached the villages of ,massa and ,st4 ,sebastiano1 covering a portion of the houses1 and1 continuing its course through an artificial foss1 or trench1 invaded cultivated ground and several villages4 ,if it had not greatly slackened after midnight1 from failure of supply at its source1 it would have reached ,naples by ,ponticelli and flowed into the sea4 ,the eruption towards the end of ,april had reached its height4 ,the ,observatory ridge was bounded on either side by two fiery streams1 which rendered the heat intolerable4 ,simultaneously with the opening of the great fissure two large craters opened at the summit1 discharging with a dreadful noise an immense cloud of smoke and ashes1 with bombs which rose to a height of #acjj metres above the brim of the volcano4#ab ,the torrents of fire which threatened ,resina1 ,bosco1 and ,torre ,annunziata1 and which devastated the fertile country of ,novelle1 ,massa1 ,st4 ,sebastiano1 and ,cerole1 and two partially buried cities1 the continual thunderings and growling of the craters1 caused such terror1 that numbers abandoned their dwellings1 flying for refuge into ,naples1 while many ,neapolitans went to ,rome or other places4 ,fortunately1 the paroxysm had now passed1 the lava-streams stopped in their course1 and the great torrent which passed the shoulders of the ,observatory through the ,fossa della ,vetraria lowered the level of its surface below that of its sides1 which appeared like two parallel ramparts above it4 ,had these streams continued to flow on the #bgth of ,april as they had done on the previous night1 they would have reached the sea1 bringing destruction to the very walls of ,naples4 ,during this eruption ,torre del ,greco was upraised to the extent of two metres1 and nearly all the houses were knocked down4 ,the igneous period of eruption having terminated1 the ashes1 lapilli1 and projectiles became more abundant1 accompanied by thunder and lightning4 ,on the #bhth they darkened the air1 and the terrific noise of the mountain continuing or increasing1 the terror at ,resina1 ,portici1 and ,naples became universal4 ,it seemed as though the tragic calamities of the eruption of ,a4,d4 #gi were about to be repeated4 ,but gradually the force of the explosions decreased1 and the noise from the crater became discontinuous1 so that on the #cjth the detonations were very few1 and by the #ast ,may the eruption was completely over4 ,such is a condensed account of one of the most formidable eruptions of our era4 ,in the frontispiece of this volume a representation1 taken 7by permission7 from a photograph by ,negretti ,zambra1 is given1 showing the appearance of ,vesuvius during the final stage of the eruption1 when prodigious masses of smoke1 steam1 and illuminated gas issued forth from the summit and overspread the whole country around with a canopy which the light of the sun could scarcely penetrate4 ,it will be noticed in the above account that1 concurrently with the full moon1 there were two distinct and special outbreaks of activity2 one occurring in ,march1 the other in the month following4 ,that the conditions of lunar and solar attraction should have a marked effect on a part of the earth's crust1 while under the tension of eruptive forces1 is only what might be expected4 ,at full moon the earth is between the sun and the moon1 and at new moon the moon is between the sun and the earth2 under these conditions 7the two bodies acting in concert7 we have spring tides in the ocean1 and a maximum of attraction on the mass of the earth4 ,hence the crust1 which at the time referred to was under tremendous strain1 only required the addition of that caused by the lunar and solar attractions to produce rupture in both cases1 giving rise to increased activity1 and the extrusion of lava and volatile matter4 ,it may1 in general1 be safely affirmed that low barometric pressure on the one hand1 and the occurrence of the syzygies 7when the attractions of the sun and moon are in the same line7 on the other1 have had great influence in determining the crises of eruptions of volcanic mountains when in a state of unrest4 ,contrast between the ,northern and ,southern ,slopes4--,before leaving ,vesuvius it may be observed that throughout all the eruptions of modern times the northern side of the mountain1 that is the old crater and flank of ,somma1 has been secure from the lava-flows1 and has enjoyed an immunity which does not belong to the southern and western side4 ,if we look at a map of the mountain showing the direction of the streams during the last three centuries1#ac we observe that all the streams of that period flowed down on the side overlooking the ,bay of ,naples2 on the opposite side the wall of ,monte di ,somma presents an unbroken front to the lava-streams4 ,from this it may be inferred that one side1 the west1 is weaker than the other2 and consequently1 when the lava and vapours are being forced upwards1 under enormous pressure from beneath1 the western side gives way under the strain1 as in the case of the fissure of #ahgb1 and the lava and vapours find means of escape4 ,from what has happened in the past it is clear that no place on the western side of the mountain is entirely safe from devastation by floods of lava2 while the prevalent winds tend to carry the ashes and lapilli1 which are hurled into the air1 in the same westerly direction4 #a ,for an excellent view of this remarkable volcanic group see ,judd's ,volcanoes1 #dth edition1 p4 #dc4 #b ,plutarch1 ,life of ,cassius2 ed4 ,reiske1 vol4 iii4 p4 #bdj4 #c ,strabo gives the following account of the appearance and condition of ,vesuvius in his day3--,supra hc loca situs est ,vesuvius mons1 agris cinctus optimis2 dempto vertice1 qui magna sui parte planus1 totus sterilis est1 adspectu sinereus1 cavernasque ostendens fistularum plenas et lapidum colore fuliginoso1 utpote ab igni exesorum4 ,ut conjectarum facere possis1 ista loca quondam arsisse et crateras ignis habuisse1 deinde materia deficiente restricta fuisse4--,rer4 ,geog41 lib4 v4 #d ,a tablet over the entrance records this act of pious liberality1 and is given by ,phillips1 loc4 cit41 p4 #ab4 #e ,the stone pine1 ,pinus pinea1 which ,turner knew how to use with so much effect in his ,italian landscapes4 #f ,bulwer ,lytton's ,last ,days of ,pompeii presents to the reader a graphic picture of the terrible event here referred to3--,the eyes of the crowd followed the gesture of the ,egyptian1 and beheld with ineffable dismay a vast vapour shooting from the summit of ,vesuvius1 in the form of a gigantic pine tree2 the trunk--blackness1 the branches--fire6 ,a fire that shifted and wavered in its hues with every moment--now fiercely luminous1 now of a dull and dying red that again blazed terrifically forth with intolerable glare6444 ,then there arose on high the shrieks of women2 the men stared at each other1 but were speechless4 ,at that moment they felt the earth shake beneath their feet2 the walls of the theatre trembled2 and beyond1 in the distance1 they heard the crash of falling roofs2 an instant more and the mountain-cloud seemed to roll towards them1 dark and rapid2 at the same time it cast forth from its bosom a shower of ashes mixed with vast fragments of burning stone4 ,over the crushing vines--over the desolate streets--over the amphitheatre itself--far and wide1 with many a mighty splash in the agitated sea1 fell that awful shower4 ,a visit to the disinterred city will probably produce on the mind a still more lasting and vivid impression of the swift destruction which overtook this city4 #g ,quoted by ,phillips1 loc4 cit41 p4 #de4 #h ,vesuvius1 p4 #gb et seq4 #i ,johnston-,lavis1 ,on the ,geology of ,monti ,somma and ,vesuvius1 ,quart4 ,jour4 ,geol4 ,soc41 vol4 #dj 7#ahhd74 #aj ,palmieri1 ,eruption of ,vesuvius in #ahgb1 with notes1 etc41 by ,robert ,mallet1 ,f4,r4,s4 ,london1 #ahgc4 #aa ,those who lost their lives were medical students1 and an ,assistant ,professor in the ,university1 ,antonio ,giannone by name4 #ab ,involving1 as ,mr4 ,mallet calculates1 an initial velocity of projection of above #fjj feet per second4 #ac ,such as that given by ,professor ,phillips in his ,vesuvius4 ,,chapter ,,ii4 ,,etna4 7a47 ,structure of the ,mountain4--,etna1 unlike ,vesuvius1 has ever been a burning mountain2 hence it was well known as such to classic writers before the ,christian era4 ,the structure and features of this magnificent mountain have been abundantly illustrated by ,elie de ,beaumont1#a ,daubeny1#b ,baron von ,waltershausen1#c and ,lyell1#d of whose writings ,i shall freely avail myself in the following account1 not having had the advantage of a personal examination of this region4 ,structure of ,etna4--,so large is ,etna that it would enclose within its ample skirts several cones of the size of ,vesuvius4 ,it rises to a height of nearly #aa1jjj feet above the waters of the ,mediterranean1#e and is planted on a floor consisting of stratified marine volcanic matter1 with clays1 sands1 and limestones of newer ,pliocene age4 ,its base is nearly circular1 and has a circumference of #hg ,english miles4 ,in ascending its flanks we pass successively over three well-defined physical zones3 the lowest1 or fertile zone1 comprising the tract around the skirts of the mountain up to a level of about #bejj feet1 being well cultivated and covered by dwellings surrounded by olive groves1 fields1 vineyards1 and fruit-trees2 the second1 or forest zone1 extending to a level of about #fbgj feet1 clothed with chestnut1 oak1 beech1 and cork trees1 giving place to pines2 and the third1 extending to the summit and called the desert region1 a waste of black lava and scori with mighty crags and precipices1 terminating in a snow-clad tableland1 from which rises the central cone1 #aajj feet high1 emitting continually steam and sulphurous vapours1 and in the course of almost every century sending forth streams of molten lava4 ,the forest zone is remarkable for the great number of minor craters which rise up from the midst of the foliage1 and are themselves clothed with trees4 ,sartorius von ,waltershausen has laid down on his map of ,etna about #bjj of these cones and craters1 some of which1 like those of ,auvergne1 have been broken down on one side4 ,many of these volcanoes of second or third magnitude lie outside the forest zone1 both above and below it2 such as the double hill of ,monti ,rossi1 near ,nicolosi1 formed in #afei1 which is #dej feet in height1 and two miles in circumference at its base4 ,sir ,c4 ,lyell observes that these minor crater-cones present us with one of the most delightful and characteristic scenes in ,europe4 ,they occur of every variety of height and size1 and are arranged in picturesque groups4 ,however uniform they may appear when seen from the sea or the plains below1 nothing can be more diversified than their shape when we look from above into their ruptured craters4 ,the cones situated in the higher parts of the forest zone are chiefly clothed with lofty pines2 while those at a lower elevation are adorned with chestnuts1 oaks1 and beech trees4 ,these cones have from time to time been buried amidst fresh lava-streams descending from the great crater1 and thus often become obliterated4 ,illustration3 ,fig4 #aj4--;,ideal ,section through ,etna4 7,after ,lyell47--,a4 ,axis of present cone of eruption2 ,b4 ,axis of extinct cone of eruption2 a4 ,older lavas1 chiefly trachytic2 b4 ,newer lavas1 erupted 7with a7 before origin of the ,val del ,bove2 c4 ,scoria and lava of recent age2 ,t4 ,tertiary strata forming the foundation to the volcanic rocks4 ,the position of the ,val del ,bove before its formation is shown by the lightly-shaded portion above ,b4 7b47 ,val del ,bove4--,the most wonderful feature of ,mount ,etna is the celebrated ,val del ,bove 7,valle del ,bue71 of which ,s4 von ,waltershausen has furnished a very beautiful plate#f--;a vast amphitheatre hewn out of the eastern flank of the mountain1 just below the snow-mantled platform4 ,it is a physical feature somewhat after the fashion of ,monte ,somma in ,vesuvius1 but exceeds it in magnitude as ,etna exceeds ,vesuvius4 ,the ,val del ,bove is about five miles in diameter1 bounded throughout three-fourths of its circumference by precipitous walls of ashes1 scori1 and lava1 traversed by innumerable dykes1 and rising inwards to a height of between #cjjj and #djjj feet4 ,towards the east the cliffs gradually fall to a height of about #ejj feet1 and at this side the vast chasm opens out upon the slope of the mountain4 ,at the head of the ,val del ,bove rises the platform1 surmounted by the great cone and crater4 ,it will thus be seen that by means of this hollow we have access almost to the very heart of the mountain4 ,what is very remarkable about the structure of this valley is that the beds exhibit the qu-qu versal dip--in other words1 they dip away on all sides from the centre--which has led to the conclusion that in the centre is a focus of eruption which had become closed up antecedently to the formation of the valley itself4 ,lyell has explained this point very clearly by showing that this focus had ceased to eject matter at some distant period1 and that the existing crater at the summit of the mountain had poured out its lavas over those of the extinct orifice4 ,this was prior to the formation of the ,val del ,bove itself2 and the question remains for consideration how this vast natural amphitheatre came to be hollowed out2 for its structure shows unquestionably that it owes its form to some process of excavation4 ,in the first place1 it is certainly not the work of running water1 as in the case of the caons of ,colorado2 the porous matter of which the mountain is formed is quite incapable of originating and supporting a stream of sufficient volume to excavate and carry away such enormous masses of matter within the period required for the purpose4 ,we must therefore have recourse to some other agency4 ,numerous illustrations are to be found of the explosive action of volcanoes in blowing off either the summits of mountains1 or portions of their sides4 ,for example1 there is reason for believing that the first result of the renewed energy of ,vesuvius was to blow into the air the upper surface of the mountain4 ,again1 so late as #ahbb1 during a violent earthquake in ,java1 a country which has been repeatedly devastated by earthquakes and volcanic eruptions1 the mountain of ,galongoon1 which was covered by a dense forest1 and situated in a fertile and thickly-peopled region1 and had never within the period of tradition been in activity1 was thus ruptured by internal forces4 ,in the month of ,july #ahbb1 after a terrible earthquake1 an explosion was heard1 and immense columns of boiling water1 mixed with mud and stones1 were projected from the mountain like a water-spout1 and in falling filled up the valleys1 and covered the country with a thick deposit for many miles1 burying villages and their inhabitants4 ,during a subsequent eruption great blocks of basalt were thrown to a distance of seven miles2 the result of all being that an enormous semicircular gulf was formed between the summit and the plain1 bounded by steep cliffs1 and bearing considerable resemblance to the ,val del ,bove4 ,other examples of the power of volcanic explosions might be cited2 but the above are sufficient to show that great hollows may thus be formed either on the summits or flanks of volcanic mountains4 ,chasms may also be formed by the falling in of the solidified crust1 owing to the extrusion of molten matter from some neighbouring vent of eruption2 and it is conceivable that by one or other of these processes the vast chasm of the ,val del ,bove on the flanks of ,etna may have been produced4 7c47 ,the ,physical ,history of ,etna4--,the physical history of ,etna seems to be somewhat as follows3-- ,first ,stage4--,somewhere towards the close of the ,tertiary period--perhaps early ,pliocene or late ,miocene--a vent of eruption opened on the floor of the ,mediterranean ,sea1 from which sheets of lava were poured forth1 and ashes mingled with clays and sands1 brought down from the neighbouring lands1 were strewn over the sea-bed4 ,during a pause in volcanic activity1 beds of limestone with marine shells were deposited4 ,second ,stage4--,this sea-bed was gradually upraised into the air1 while fresh sheets of lava and other ejecta were accumulated round the vents of eruption1 of which there were two principal ones--the older under the present ,val del ,bove1 the newer under the summit of the principal cone4 ,thus was the mountain gradually piled up4 ,third ,stage4--,the vent under the ,val del ,bove ceased to extrude more matter1 and became extinct4 ,meanwhile the second vent continued active1 and1 piling up more and more matter round the central crater1 surmounted the former vent1 and covered its ejecta with newer sheets of lava1 ashes1 and lapilli1 while numerous smaller vents1 scattered all over the sides of the mountain1 gave rise to smaller cones and craters4 ,fourth ,stage4--,this stage is signalised by the formation of the ,val del ,bove through some grand explosion1 or series of explosions1 by which this vast chasm was opened in the side of the mountain1 as already explained4 ,fifth ,stage4--,this represents the present condition of the mountain1 whose height above the sea is due1 not only to accumulation of volcanic materials round the central cone1 but to elevation of the whole island1 as evinced by numerous raised beaches of gravel and sand1 containing shells and other forms of marine species now living in the waters of the ,mediterranean4#g ,since then the condition and form of the mountain has remained very much the same1 varied only by the results of occasional eruptions4 7d47 ,dissimilarity in the ,constitution of the ,lavas of ,etna and ,vesuvius4--,before leaving the subject we have been considering1 it is necessary that ,i should mention one remarkable fact connected with the origin of the lavas of ,etna and ,vesuvius respectively2 ,i refer to their essential differences in mineral composition4 ,it might at first sight have been supposed that the lavas of these two volcanic mountains--situated at such a short distance from each other1 and evidently along the same line of fracture in the crust--would be of the same general composition2 but such is not the case4 ,in the lava of ,vesuvius leucite is an essential1 and perhaps the most abundant mineral4 ,it is called by ,zirkel ,sanidin-,leucitgestein4 7,see ,plate ,,iv47 ,but in that of ,etna this mineral is 7as far as ,i am aware7 altogether absent4 ,we have fortunately abundant means of comparison1 as the lavas of these two mountains have been submitted to close examination by petrologists4 ,in the case of the ,vesuvian lavas1 an elaborate series of chemical analyses and microscopical observations have been made by the ,rev4 ,professor ,haughton1 of ,dublin ,university1 and the author1#h from specimens collected by ,professor ,guiscardi from the lava-flows extending from #afca to #ahfh1 in every one of which leucite occurs1 generally as the most abundant mineral1 always as an essential constituent4 ,on the other hand1 the composition of the lavas of ,etna1 determined by ,professor ,a4 von ,lasaulx1 from specimens taken from the oldest 7vortnischen7 sheets of lava down to those of the present day1 indicates a rock of remarkable uniformity of composition1 in which the components are plagioclase felspar1 augite1 olivine1 magnetite1 and sometimes apatite2 but of leucite we have no trace4#i ,in fact1 the lavas of ,etna are very much the same in composition as the ordinary basalts of the ,british ,isles1 while those of ,vesuvius are of a different type4 ,this seems to suggest an origin of the two sets of lavas from a different deep-seated magma2 the presence of leucite in such large quantity requiring a magma in which soda is in excess1 as compared with that from which the lavas of ,etna have been derived4#aj #a ,mmoires pour ,servir1 etc41 vol4 ii4 #b ,daubeny1 ,volcanoes1 p4 #bgj4 #c ,von ,waltershausen1 ,der tna1 edited by ,a4 von ,lasaulx4 #d ,lyell1 ,principles of ,geology1 vol4 ii41 edition #ahgb4 #e ,its height1 as determined by ,captain ,smyth in #ahge trigonometrically1 was #aj1hgd feet1 and afterwards by ,sir ,j4 ,herschel barometrically1 #aj1hgb feet4 #f ,atlas des tna 7,weimar1 #aheh71 in which the different lava-streams of #afhh1 #ahjb1 #ahji1 #ahaa1 #ahai1 #ahbd1 and #ahch are delineated4 #g ,sir ,william ,hamilton observes that history is silent regarding the first eruptions of ,etna4 ,it was in activity before the ,trojan ,war1 and even before the arrival of the ,sizilien settlers4 ,diodorus and ,thucydides notice the earliest recorded eruptions1 those from #ggb to #chh ,b4,c41 during which time the mountain was thrice in eruption4 ,later eruptions took place in the year #adj1 #ace1 #abe1 #abb ,b4,c4 ,in the year #dd ,b4,c41 in the reign of ,julius ,csar1 there was a very violent outburst of volcanic activity4--,neuere ,beobachtungen ber die ,vulkane ,italiens und am ,rhein1 p4 #agc1 ,frankfurt 7#aghd74 #h ,report on the ,chemical and ,mineralogical ,characters of the ,lavas of ,vesuvius from #afca to #ahfh1 ,transactions of the ,royal ,irish ,academy1 vol4 xxvi4 7#ahgf74 ,in the lava of #ahdh leucite was found to reach #dd4i per cent4 of the whole mass4 ,in that of ,granatello1 #afca1 it reaches its lowest proportion--viz41 #c4cg per cent4 #i ,a4 von ,lasaulx1 in ,von ,waltershausen's ,der tna1 ,book ,,ii41 x4 #dbc4 #aj ,the view of ,professor ,judd1 that leucite easily changes into felspar1 and that some ancient igneous rocks which now contain felspar were originally leucitic1 does not seem to be borne out by the above facts4 ,in such cases the felspar crystals ought to retain the forms of leucite4 ,see ,volcanoes1 #dth edition1 p4 #bfh4 ,,chapter ,,iii4 ,,the ,,lipari ,,islands1 ,,stromboli4 7a47 ,a brief account of this remarkable group of volcanic islands must here be given1 inasmuch as they seem to be representatives of a stage of volcanic action in which the igneous forces are gradually losing their energy4 ,according to ,daubeny1 the volcanic action in these islands seems to be developed along two lines1 nearly at right angles to each other1 one parallel to that of the ,apennines1 beginning with ,stromboli1 intersecting ,panaria1 ,lipari1 and ,vulcano2 the other extending from ,panaria to ,salina1 ,alicudi1 and ,felicudi1 and again visible in the volcanic products which make their appearance at ,ustica4 7,see ,map1 ,fig4 #aa47 ,the islands lie between the north coast of ,sicily and that of ,italy1 and from their position seem to connect ,etna with ,vesuvius2 but this is very problematical1 as would appear from the difference of their lavas4 ,the principal islands are those of ,stromboli1 ,panaria1 ,lipari1 ,vulcano1 ,salina1 ,felicudi1 and ,alicudi4 ,these three last are extinct or dormant1 but ,salina contains a crater1 rising1 according to ,daubeny1 not less than #cejj feet above the sea4#a ,vulcano 7referred to by ,strabo under the name of ,hiera7 consists of a crater which constantly emits large quantities of sulphurous vapours1 but was in a state of activity in the year #aghf1 when1 after frequent earthquake shocks and subterranean noises1 it vomited forth during fifteen days showers of sand1 together with clouds of smoke and flame1 altering materially the shape of the crater from which they proceeded4 ,illustration3 ,,lipari ,,islands4 ,fig4 #aa4--,map to show the position of these islands1 showing the branching lines of volcanic action--one parallel to that of the ,apennines1 the other stretching westwards at right angles thereto4 ,the islands of ,lipari are formed of beds of tuff1 penetrated by numerous dykes of lava1 from which uprise two or three craters1 formed of pumice and obsidian passing into trachyte4 ,volcanic operations might have here been said to be extinct1 were it not that their continuance is manifested by the existence of hot springs and stufes1 or vapour baths1 at ,st4 ,calogero1 about four miles from the town of ,lipari4 ,daubeny considers it not improbable that this island may have had an active volcano even within the historical period1 a view which is borne out by the statement of ,strabo4#b ,illustration3 ,fig4 #ab4--;,island of ,vulcano1 one of the ,lipari ,group1 in eruption4--7,after ,sir ,w4 ,hamilton47 7b47 ,but by far the most remarkable island of the group1 as regards its present volcanic condition1 is ,stromboli1 which has ever been in active eruption from the commencement of history down to the present day4 ,professor ,judd1 who visited this island in #ahgd1 and has produced a striking representation of its aspect1#c gives an account of which ,i shall here avail myself4#d ,the island is of rudely circular outline1 and rises into a cone1 the summit of which is #cjij feet above the level of the ,mediterranean4 ,from a point on the side of the mountain masses of vapour are seen to issue1 and these unite to form a cloud over the summit2 the outline of this vapour-cloud varying continually according to the hygrometric state of the atmosphere1 and the direction and force of the wind4 ,at the time of ,professor ,judd's visit1 the vapour-cloud was spread in a great horizontal stratum overshadowing the whole island2 but it was clearly seen to be made up of a number of globular masses1 each of which is a product of a distinct outburst of volcanic forces4 ,viewed at night-time1 ,stromboli presents a far more striking and singular spectacle4 ,when watched from the deck of a vessel1 a glow of red light is seen to make its appearance from time to time above the summit of the mountain2 it may be observed to increase gradually in intensity1 and then as gradually to die away4 ,after a short interval the same appearances are repeated1 and this goes on till the increasing light of dawn causes the phenomenon to be no longer visible4 ,the resemblance presented by ,stromboli to a flashing light on a most gigantic scale is very striking1 and the mountain has long been known as the lighthouse of the ,mediterranean4 ,the mountain is built up of ashes1 slag1 and scori1 to a height of 7as already stated7 over #cjjj feet above the surface of the sea2 but1 as ,professor ,judd observes1 this by no means gives a just idea of its vast bulk4 ,soundings in the sea surrounding the island show that the bottom gradually shelves around the shores to a depth of nearly #fjj fathoms1 so that ,stromboli is a great conical mass of cinders and slaggy materials1 having a height above its floor of about #ffjj feet1 and a base the diameter of which exceeds four miles4 ,the crater of ,stromboli is situated1 not at the apex of the cone1 but at a distance of #ajjj feet below it4 ,the explosions of steam1 accompanied by the roaring as of a smelting furnace1 or of a railway engine when blowing off its steam1 are said by ,judd to take place at very irregular intervals of time1 varying from less than one minute to twenty minutes1 or even more4 ,on the other hand1 ,hoffmann describes them as occurring at perfectly regular intervals1 so that1 perhaps1 some variation has taken place within the interval of about forty years between each observation4 ,both observers agree in stating that lava is to be seen welling up from some of the apertures within the crater1 and pouring down the slope towards the sea1 which it seldom or never reaches4#e ,the intermittent character of these eruptions appears to be due1 as ,mr4 ,scrope has suggested1 to the exact proportion between the expansive and repressive forces2 the expansive force arising from the generation of a certain amount of aqueous vapour and of elastic gas2 the repressive1 from the pressure of the atmosphere and from the weight of the superincumbent volcanic products4 ,steam is here1 as in a steam-engine1 not the originating agent in the phenomena recorded2 but the result of water coming in contact with molten lava constantly welling up from the interior1 by which it is converted into steam1 which from time to time acquires sufficient elastic force to produce the eruptions2 the water being obviously derived from the surrounding sea1 which finds its way by filtration through fissures1 or through the porous mass of which the mountain is formed4 ,were it not for the access of water this volcano would probably appear as a fissure-cone extruding a small and continuous stream of molten lava4 ,the adventitious access of the sea water gives rise to the phenomena of intermittent explosions4 ,the vitality of the volcano is therefore due1 not to the presence of water1 but to the welling up of matter from the internal reservoir through the throat of the volcano4 ,pantelleria4--,this island1 lying between the coast of ,sicily and ,cape ,bon in ,africa1 is wholly volcanic4 ,it has a circumference of thirty miles1 and from its centre rises an extinct crater-cone to a height of about #cjjj feet4 ,the flanks of this volcano are diversified by several fresh craters and lava-streams1 while hot springs burst out with a hissing noise on its southern flank1 showing that molten matter lies below at no very great depth4 ,this island probably lies along the dividing line between the non-volcanic and volcanic region of the ,mediterranean1 and is consequently liable to intermittent eruptions4 ,it was at a short distance from this island that the remarkable submarine outburst of volcanic forces took place on ,october #agth1 #ahia1 for an account of which we are indebted to ,colonel ,j4 ,c4 ,mackowen4#f ,on that day1 after a succession of earthquake shocks1 the inhabitants were startled by observing a column of smoke rising out of the sea at a distance of three miles1 in a north-westerly direction4 ,the ,governor1 ,francesco ,valenza1 having manned a boat1 rowed out towards the fiery column1 and on arriving found it to consist of black scoriaceous bombs1 which were being hurled into the air to a height of nearly thirty yards2 some of them burst in the air1 others1 discharging steam1 ran hissing over the water2 many of them were very hot1 some even red-hot4 ,one of these bombs1 measuring two feet in diameter1 was captured and brought to shore4 ,it was observed that after the eruption the earthquake shocks ceased4 ,a vast amount of material was cast out of the submarine crater1 forming an island #ejj yards in length and rising up to nine feet above the surface1 but after a few days it was broken up and dispersed over the sea-bed by the action of the waves4 #a ,volcanoes1 p4 #bfb4 ,these islands are described by ,hoffmann1 ,poggendorf ,annal41 vol4 xxvi4 7#ahcb72 also by ,lyell1 ,principles of ,geology1 vol4 ii41 and by ,judd1 who personally visited them1 and gives a very vivid account of their appearance and structure4 #b ,strabo1 lib4 vi4 #c ,judd1 ,volcanoes1 p4 #h4 #d ,stromboli has also been described by ,spallanzani1 ,hoffmann1 ,daubeny1 and others4 ,the account of ,judd is the most recent4 ,of this island ,strabo says1 ,strongyle a rotundate figur sic dicta1 ignita ipsa quoque1 violentia flammarum minor1 fulgore excellens2 ibi habitasse colum ajunt4--,lib4 vi4 #e ,poggend4 ,annal41 vol4 xxvi41 quoted by ,daubeny4 #f ,communicated by ,captain ,petrie to the ,victoria ,institute1 #ast ,february #ahib4 ,see also a detailed and illustrated account of the eruption communicated by ,a4 ,ricco to the ,annali dell' ,ufficio centrale ,meteorologico e ,geodonamico1 ,ser4 ii41 ,parte #c1 vol4 xi4 ,summarised by ,mr4 ,butler in ,nature1 ,april #ba1 #ahib4 ,,chapter ,,iv4 ,,the ,,santorin ,,group4 ,illustration3 ,fig4 #ac4--;,ideal ,section through the ,gulf of ,santorin1 to show the structure of the submerged volcano4--a4 ,island of ,aspronisi2 b4 ,island of ,thera2 #a4 ,old ,kaimeni ,island2 #b4 ,new ,kaimeni ,island2 #c4 ,little ,kaimeni ,island4 7a47 ,before leaving the subject of ,european active volcanoes1 it is necessary to give some account of the remarkable volcanic island of ,santorin1 in the ,grecian archipelago4 ,this island for #bjjj years has been the scene of active volcanic operations1 and in its outline and configuration1 both below and above the surface of the ,mediterranean1 presents the aspect of a partially submerged volcanic mountain4 7,see ,section1 ,fig4 #ac47 ,if1 for example1 we can imagine the waters of the sea to rise around the flanks of ,vesuvius until they have entered and overflowed to some depth the interior caldron of ,somma1 thus converting the old crater into a crescent-shaped island1 and the cone of ,vesuvius into an island--or group of islands--within the caldron1 then we shall form some idea of the appearance and structure of the ,santorin group4 ,form of the ,group4--,the principal island1 ,thera1 has somewhat the shape of a crescent1 breaking off in a precipitous cliff on the inner side1 but on the outer side sloping at an angle of about fifteen degrees into deep water4 ,continuing the curvature of the crescent1 but separated by a channel1 is the island of ,therasia2 and between this and the southern promontory of ,thera is another island called ,aspronisi4 ,all these islands1 if united1 would form the rim of a crater1 in which the volcanic matter slopes outward into deep water1 descending at a short distance to a depth of #bjj fathoms and upwards4 ,in the centre of the gulf thus formed rise three islands1 called the ,old1 ,new1 and ,little ,kaimenis4 ,these may be regarded as cones of eruption1 which history records as having been thrown up at successive intervals4 ,according to ,pliny1 the year #ahf ,b4,c4 gave birth to ,old ,kaimeni1 also called ,hiera1 or the ,sacred ,isle2 and in the first year of our era ,thera 7the ,divine7 made its appearance above the water1 and was soon joined to the older island by subsequent eruptions4 ,old ,kaimeni also increased in size by the eruptions of #gbf and #adbg4 ,a century and a half later1 in #aegc1 another eruption produced the cone and crater called ,micra-,kaimeni4 ,thus were formed1 or rather were rendered visible above the water1 the central craters of eruption2 and between these and the inner cliff of ,thera and ,therasia is a ring of deep water1 descending to a depth of over #bjj fathoms4 ,so that1 were these islands raised out of the sea1 we should have presented to our view a magnificent circular crater about six miles in diameter1 bounded by nearly vertical walls of rock from #ajjj to #aejj feet in height1 and ruptured at one point1 from the centre of which would rise two volcanic cones--namely1 the ,kaimenis--one with a double crater1 still foci of eruption1 and from time to time bursting forth in paroxysms of volcanic energy1 of which those of #afej1 #agjg1 and #ahff were the most violent and destructive4#a ,of this last ,i give a bird's-eye view 7,fig4 #ad74 ,the only rock of non-volcanic origin in these islands consists of granular limestone and clay slate forming the ridge of ,mount ,st4 ,elias1 which rises to a height of #ahhg feet at the south-eastern side of the island of ,thera1 crossing the island from its outer margin nearly to the interior cliff1 so that the volcanic materials have been piled up along its sides4 ,the rocks of ,st4 ,elias are much more ancient than any of the volcanic materials around2 and1 as ,bory ,st4 ,vincent has shown1 have been subjected to the same flexures1 dip and strike1 as those sedimentary rocks which go to form the non-volcanic islands of the ,grecian archipelago4 ,illustration3 ,fig4 #ad4--;,bird's-eye ,view of the ,gulf of ,santorin during the volcanic eruption of ,february #ahff4--7;,after ,lyell47 ,illustration3 ,ground ,plan of ,rocca ,monfina ,fig4 #ae4--,rocca ,monfina1 in ,southern ,italy1 showing a crater-ring of trachytic tuffs1 from the midst of which1 according to ,judd1 an andesite lava-cone has been built up4 ,compare with the ,santorin ,group4 7b47 ,origin of the ,santorin ,group4--,in reference to the origin of the ,santorin group1 ,lyell regards it as a remnant of a great volcanic mountain which possessed a focus of eruption rising in the position of the present foci1 but afterwards partially destroyed and the whole submerged to a depth of over #ajjj feet4 ,but another explanation is open to us1 and one not inconsistent with what we now know of the physical changes to which the ,mediterranean has been subjected since early ,tertiary times4 ,to my mind it is difficult to conceive how such a volcanic mountain as that of ,santorin could have been formed under water2 while1 on the other hand1 its physical structure and contour bear so striking a resemblance 7as already observed7 to those of ,vesuvius and ,rocca ,monfina that we are much tempted to infer that it had a somewhat similar origin4 ,now we know that ,vesuvius was built up by means of successive eruptions taking place under the air2 and the question arises whether it could be possible that ,santorin had a similar origin owing to the waters of the ,mediterranean having been temporally lowered at a later ,tertiary epoch4 ,it has been stated by ,m4 ,fouqu that the age of the more ancient volcanic beds of ,santorin belong1 as shown by the included fossils1 to the newer ,pliocene epoch4 ,these are of course the unsubmerged1 and therefore more recent strata1 and may have been recently upheaved during one or more of the outbursts of volcanic energy4 ,but it seems an impossibility that the ,gulf of ,santorin1 with its precipitous walls and deep circular interior channel1 as shown by the ,ideal ,section 7,fig4 #ac71 could have been formed otherwise than under the air4 ,we are led1 therefore1 to inquire whether there was a time in the history of the ,mediterranean1 since the ,eocene period1 when the waters were lower than at present4 ,that this was the case we have clear evidence4 ,the remains of elephants1 hippopotami1 and other animals1 which have been discovered in great numbers in the ,maltese caves1 show that this island was united to ,sicily1 and this again to ,europe1 during the later ,pliocene epoch1 so as to have become the abode of an ,europasian fauna4 ,according to ,dr4 ,wallace1 a causeway of dry land existed1 stretching from ,italy to ,tunis in ,north ,africa through the ,maltese ,islands--an inference involving the lowering of the waters of the ,mediterranean by several hundred feet4#b ,there is every reason for supposing that the old volcano of ,santorin was in active eruption at this period2 and its history may be considered to be similar to that of ,vesuvius until1 at the rising of the waters during the ,pluvial 7or ,post-,pliocene7 epoch1 during which they rose higher than at present1 ,santorin was converted into a group of islands1 slightly differing in form from those of the present day4 ,this view seems to meet the difficulties regarding the origin of this group1 difficulties which ,lyell had long since clearly recognised4 7c47 ,limit of the ,mediterranean ,volcanic ,region4--,with the ,santorin group we conclude our account of the active ,european volcanoes4 ,it may be observed1 however1 that from some cause not ascertained the volcanic districts of the ,mediterranean and its shores are confined to the north side of that great inland sea2 so that as regards vulcanicity the ,african coast presents a striking contrast to that of the opposite side4 ,if we draw a line from the shores of the ,levant to the ,straits of ,gibraltar1 by ,candia1 ,malta1 and to the south of ,pantelleria and ,sardinia1 we shall find that the volcanic islands and districts of the mainland lie to the north of it4#c ,this has doubtless some connection with the internal geological structure4 ,the immunity of the ,libyan desert from volcanic irruptions is in keeping with the remarkably undisturbed condition of the ,secondary strata1 which seldom depart much from the horizontal position2 while the igneous rocks of the ,atlas mountains are probably of great geological antiquity4 ,on the other hand1 the ,secondary and ,tertiary formations of the northern shores and islands of the ,mediterranean are generally characterised by the highly-inclined1 flexured1 and folded position of the strata4 ,hence we may suppose that the crust over the region lying to the north of the volcanic line1 owing to its broken and ruptured condition1 was less able to resist the pressure of the internal forces of eruption than that lying to the south of it2 and that1 in consequence1 vents and fissures of eruption were established over the former of these regions1 while they are absent in the latter4 #a ,fuller details will be found in ,daubeny's ,volcanoes1 chap4 xviii41 and ,lyell's ,principles of ,geology1 vol4 ii4 p4 #fe 7edition #ahgb74 ,the bird's-eye view is taken from this latter work by kind permission of the publisher1 ,mr4 ,j4 ,murray1 as also the accompanying ,ideal ,section1 ,fig4 #ac4 #b ,wallace1 ,geographical ,distribution of ,animals 7#ahgf74 ,the author's ,sketch of ,geological ,history1 p4 #acj 7,deacon ,co41 #ahhg74 #c ,the volcanic area lying to the north of this line will include ,sardinia1 ,sicily1 ,pantelleria1 the ,grecian ,archipelago1 ,asia ,minor1 and ,syria2 the non-volcanic area lying to the south of this line will include the ,african coast1 ,malta1 ,isles of ,crete and ,cyprus4 ,the ,isle of ,pantelleria is apparently just on the line1 which1 continued eastward1 probably follows the north coast of ,cyprus1 parallel to the strike of the strata and of the central axis of that island4--,see ,carte ,gologique de l'le de ,chypre1 par ,,mm4 ,albert ,gaudry et ,amede ,damour 7#ahfj74 ,,chapter ,v4 ,,european ,,extinct ,,or ,,dormant ,,volcanoes4 ,we are naturally led on from a consideration of the active volcanoes of ,europe to that of volcanoes which are either dormant or extinct in the same region4 ,such are to be found in ,italy1 ,central ,france1 both banks of the ,rhine and ,moselle1 the ,westerwald1 ,vogelsgebirge1 and other districts of ,germany2 in ,hungary1 ,styria1 and the borders of the ,grecian archipelago4 ,but the subject is too large to be treated here in detail2 and ,i propose to confine my observations to some selected cases which are to be found in ,southern ,italy1 ,central ,france1 and the ,rhenish districts1 where the volcanic features are of so recent an age as to preserve their outward form and structure almost intact4 7a47 ,southern ,italy4--,extinct volcanoes and volcanic rocks occupy considerable tracts between the western flanks of the ,apennines and the ,mediterranean coast in the ,neapolitan and ,roman ,states1 forming the remarkable group of the ,phlegran fields 7,campi ,phlegri71 with the adjoining islands of ,ischia1 ,procida1 ,nisida1 ,vandolena1 ,ponza1 and ,palmarola2 at ,melfi and ,avellino4 ,all the region around ,rome extending along the western slopes of the ,apennines from ,velletri to ,orvieto1 together with ,mount ,annato in ,tuscany1 is formed of volcanic material1 and the same may be said of a large part of the island of ,sardinia4 ,from these districts ,i shall select some points which seem to be of special interest4 ,monte ,nuovo and the ,phlegran ,fields4--,the tract of which this celebrated district forms a part lies as it were in a bay of the ,apennine limestone of ,jurassic age4 ,the floor of this bay is composed of puzzolana1 a name given to beds of volcanic tuff of great thickness1 and rising into considerable hills in the vicinity of the city of ,naples1 such as that of ,st4 ,elmo4 ,its composition is peculiar1 as it is chiefly formed of small pieces of pumice1 obsidian1 and trachyte1 in beds alternating with loam1 ferriferous sand1 and fragments of limestone4 ,it is evidently of marine formation1 as ,sir ,william ,hamilton1 ,professor ,pilla1 and others have detected sea-shells therein1 of the genera ,ostra1 ,cardium1 ,pecten and ,pectunculus1 ,buccinum1 etc4 ,it is generally of a greyish colour1 and sometimes sufficiently firm to be used as a building stone4 ,the ,roman ,campagna is largely formed of similar materials1 which were deposited at a time when the districts in question were submerged1 and matter was being erupted from volcanic vents at various points around1 and spread over the sea-bed4 ,such is the character of the general floor on which the more recent crater-cones of this district have been built4 ,these are numerous1 and all extinct with the exception of the ,solfatara1 near ,puzzuoli1 from which gases mixed with aqueous vapour are continually being exhaled4 ,the gases consist of sulphuretted hydrogen mixed with a minute quantity of muriatic acid4#a ,this district is also remarkable for containing several lakes occupying the interiors of extinct craters2 amongst others1 ,lake ,avernus1 which1 owing to its surface having been darkened by forests1 and in consequence of the effluvia arising from its stagnant waters1 has had imparted to it a character of gloom and terror1 so that ,homer in the ,odyssey makes it the entrance to hell1 and describes the visit of ,ulysses to it4 ,virgil follows in his steps4 ,another lake of similar origin is ,lake ,agnano4 ,here also is the ,grotto del ,cane1 a cavern from which are constantly issuing volumes of carbonic acid gas combined with much aqueous vapour1 which is condensed by the coldness of the external air1 thus proving the high temperature of the ground from which the gaseous vapour issues4 ,this whole volcanic region1 so replete with objects of interest1#b may be considered1 as regards its volcanic character1 in a moribund condition2 but that it is still capable of spasmodic movement is evinced by the origin of ,monte ,nuovo1 the most recent of the crater-cones of the district4 ,this mountain1 rising from the shore of the ,bay of ,bai1 was suddenly formed in ,september #bith1 #aech1 and rises to a height of #ddj feet above the sea-level4 ,it is a crater-cone1 and the depth of the crater has been determined by the ,italian mineralogist ,pini to be #dba ,english feet2 its bottom is thus only #ai feet above the sea-level4 ,a portion of the base of the cone is considered partly to occupy the site of the ,lucrine ,lake1 which was itself nothing more than the crater of a pre-existent volcano1 and was almost entirely filled up during the explosion of #aech4 ,monte ,nuovo is composed of ashes1 lapilli1 and pumice-stones2 and its sudden formation1 heralded by earthquakes1 and accompanied by the ejection of volcanic matter mixed with fire and water1 is recorded by ,falconi1 who vividly depicts the terror and consternation of the inhabitants of the surrounding country produced by this sudden and terrible outburst of volcanic forces4#c 7b47 ,central ,italy and the ,roman ,states4--,the tract bordering the western slopes of the ,apennines northward from ,naples into ,tuscany1 and including the ,roman ,states1 is characterised by volcanic rocks and physical features of remarkable interest and variety4 ,these occur in the form of extinct craters1 sometimes filled with water1 and thus converted into circular lakes2 or of extensive sheets and conical hills of tuff2 or1 finally1 of old necks and masses of trachyte and basalt1 sometimes exhibiting the columnar structure4 ,the ,eternal ,city itself is built on hills of volcanic material which some observers have supposed to be the crater of a great volcano2 but ,ponzi1 ,brocchi1 and ,daubeny all concur in the opinion that this is not the case1 as will clearly appear from the following account4 ,the geological structure of the valley of the ,tiber at ,rome is very clearly described by ,professor ,ponzi in a memoir published in #ahej1 from which the accompanying section is taken4#d 7,fig4 #af47 ,from this it will be seen that the ,seven-hilled ,city is built upon promontories of stratified volcanic tuff1 of which the ,campagna is formed1 breaking off along the banks of the ,tiber1 the hills being the result of the erosion1 or denudation1 of the strata along the side of the river valley4 ,as the strata dip from west to east across the course of the river1 it follows that those on the western banks are below those on the opposite side2 and thus the marine sands and marls which underlie the volcanic tuff1 and are concealed by it along the eastern side of the valley1 emerge on the west1 and form the range of hills on that side4 ,such being the structure of the formations under ,rome1 it is evident that it is not built on a volcano4 ,illustration3 ,fig4 #af4--;,geological ,section across the ,valley of the ,tiber at ,rome4 #a4 ,alluvium of the ,tiber2 #b4 ,diluvium2 #c4 ,volcanic tuff 7recent deposits72 #d4 ,sands1 etc42 #e4 ,blue marl 7sub-,apennine deposits74 ,the tuff contains fragments of lava and pebbles of ,apennine limestone1 and was deposited under the waters of an extensive lake at a time when volcanic action was rife amidst the ,alban ,hills4 ,this lacustrine formation rests in turn on deposits of marine origin1 containing oysters1 patell1 and other sea-shells1 of which the chain of hills on the right bank of the ,tiber is chiefly formed4 ,the district around ,albano lying to the south of ,rome is of peculiar interest from the assemblage of old crater-lakes which it contains2 as1 for instance1 those of ,albano1 ,vallariccia1 ,nemi1 ,juturna1 and the lake of ,gabii4 ,the lake of ,albano1 one of the most beautiful sheets of water in the world1 is about six miles in circumference1 and surrounded by beds of peperino1 a variety of tuff presenting a bright1 undecomposed aspect when newly broken4 ,the level of this lake was lowered by the ,romans during the siege of ,veii by means of a tunnel1 so that the waters are #bjj feet lower than the level at which they originally stood4 ,in the same district is the lake of ,nemi1 very regular in its circular outline2 that of ,juturna lying near the foot of the ,alban ,hills1 and that of ,ariccia lying in a deep hollow eight miles in circumference2--all may be supposed to have been the craters of extinct volcanoes1 both by reason of their shape and of the materials of which they are formed4 ,all these old craters are1 however1 according to ,daubeny1 only the dependencies and offshoots1 as it were1 of the great extinct volcano1 the traces of which still remain upon the summit of the ,alban ,hills1 and which is comparable in its form to that of ,vesuvius1 as it is surrounded by an outer circle of volcanic rock comparable to that of ,somma4#e ,to the north of the city of ,rome are several crateriform lakes1 some of which are of great size1 such as that of ,bolsena1 over twenty miles in circumference1 and the ,lago di ,bracciano1 almost as large1 and lying about twelve miles from the city4 ,these extensive sheets of water are surrounded by banks of tuff and volcanic sand1 in which fragments of augite1 leucite1 and crystals of titanite are distributed4 ,the town of ,viterbo is built up at the foot of a steep hill called ,monte ,cimini1 the lower part of which is composed of trachyte2 this is surmounted by tuff1 which appears to have been ejected from an extinct crater occupying the summit of the mountain1 and now converted into a lake called the ,lake of ,vico4 ,this crater is perfectly circular1 and from its centre rises a little conical hill covered by trees4 7c47 ,physical ,history4--,space does not permit of a fuller description of the remarkable volcanic features of the tract lying along the western slope of the ,apennines2 but from what has been stated it will be clear that volcanic forces have been in operation at one time on a grand scale in the ,roman ,states and the ,south of ,tuscany1 over a tract extending from ,mount ,annato to ,velletri and ,segni4 ,this tract was separated from that of the ,neapolitan volcanic region by a range of limestone hills of ,jurassic age between ,segni and ,gaeta1 a protrusion of the ,alban ,hills westward2 but the general structure and physical history of both regions are probably very similar1 with the exception that the igneous forces still retain their vitality in the more southerly region4 ,in the case of the ,roman volcanic district1 a bay seems to have been formed about the close of the ,miocene period1 bounded on all sides but the west by hills of limestone1 over whose bed strata of marl1 sandstone1 and conglomerate were deposited4 ,this tract was converted by subsequent movements into a fresh-water lake1 and contemporaneously volcanic operations commenced over the whole region1 and beds of tuff1 often containing blocks of rock ejected from neighbouring craters1 were deposited over those of marine origin4 ,meanwhile numerous crater-cones were thrown up2 and1 as the land gradually rose1 the waters of the lake were drained off1 leaving dry the ,campagna and plain of the ,tiber4 ,ultimately the volcanic fires smouldered down and died out1 whether within the historic epoch or not is uncertain2 lakes were formed within the now dormant craters1 and the face of nature gradually assumed a more placid and less forbidding aspect over this memorable region1 destined to be the site of ,rome1 the ,mistress of the ,world4 #a ,as determined by ,daubeny in #ahbe4 #b ,including the ruins of the ,temple of ,serapis1 whose pillars are perforated by marine boring shells up to a height of about #af feet from their base2 indicating that the land had sunk down beneath the sea1 and afterwards been elevated to its present level4 #c ,the account of ,falconi1 and another by ,pietro ,giacomo di ,toledo1 are given by ,sir ,w4 ,hamilton1 op4 cit41 p4 #aih1 and also reproduced by ,sir ,c4 ,lyell1 ,principles1 vol4 i4 p4 #fjh4 #d ,guiseppe ,ponzi1 ,sulla storia fisica del ,bacino di ,roma1 ,annali di ,scienze ,fisiche 7,roma1 #ahej74 #e ,daubeny1 ,volcanoes1 p4 #aga4 ,,chapter ,,vi4 ,,extinct ,,volcanoes ,,of ,,central ,,france4 7a47 ,general ,structure of the ,auvergne ,district4--,from a granitic and gneissose platform situated near the centre of ,france1 and separated from the western spurs of the ,alps by the wide valley of the ,rhone1 there rises a group of volcanic mountains surpassing in variety of form and structure any similar mountain group in ,europe1 and belonging to an epoch ranging from the ,middle ,tertiary down almost to the present day4 ,this volcanic group of mountains gives rise to several important rivers1 such as the ,loire1 the ,allier1 the ,soule 7a branch of the ,loire71 the ,creuse1 the ,dordogne1 and the ,lot2 and in the ,plomb du ,cantal attains an elevation of #facj feet above the sea4 ,its southern section1 that of ,mont ,dore1 the ,cantal1 and the ,haute ,loire1 is characterised by magnificent valleys1 traversing plateaux of volcanic lava1 and exhibiting the results of river erosion on a grand scale2 while its northern section1 that of the ,puy de ,dme1 presents to us a varied succession of volcanic crater-cones and domes1 with their extruded lava-streams1 almost as fresh and unchanged in form as if they had only yesterday become extinct4 ,a somewhat similar1 but less important1 chain of extinct volcanoes also occurs in the ,velay and ,vivarais1 between the upper waters of the ,loire and the ,allier1 in the vicinity of the town of ,le ,puy4#a ,the principal city in this region is ,clermont-,ferrand1 lying near the base of the ,puy de ,dme1 and ever memorable as the birthplace of ,blaise ,pascal4#b ,illustration3 ,fig4 #ag4--;,generalised ,section through the ,puy de ,dme and ,vale of ,clermont1 distance about ten miles4 ,the general floor formed of granite and gneiss 7,g72 ,d4 ,domite-lava of the ,puy de ,dme2 ,sc4 ,cones of ashes and scori2 ,l4 ,lava-sheets2 ,a4 ,alluvium of the ,vale of ,clermont and ,lake deposits4 ,the physical structure of this region is on the whole very simple4 ,the fundamental rocks consist of granite and gneiss passing into schist1 all of extreme geological antiquity1 forming a vast platform gradually rising in a southerly direction towards the head waters of the ,loire and the ,allier in the ,departments of ,haute ,loire1 ,lozre1 and ,ardche4 ,on this platform are planted the whole of the volcanic mountains4 7,see ,fig4 #ag47 ,the granitic plateau is bounded on the east1 throughout a distance of about #ej miles1 by the wide and fertile plain of ,clermont1 watered by the ,allier and its numerous branches descending from the volcanic mountains1 and is about #be miles in width from east to west in the parallel of ,clermont1 but gradually narrowing in a southerly direction1 till at ,brioude it becomes an ordinary mountain ravine4 ,the eastern margin of the plain is formed by another granitic ridge expanding into a plateau towards the south1 and joining in with that already described2 but towards the north and directly east of ,clermont it forms a high ridge traversed by the railway to ,st4 tienne and ,lyons1 and descending towards the east into the valley of the ,loire4 ,no more impressive view is to be obtained of the volcanic region than that from the summit of this second ridge1 on arriving there towards evening from the city of ,lyons4 ,at your feet lies the richly-cultivated plain of ,clermont1 dotted with towns1 villages1 and hamlets1 and decorated with pastures1 orchards1 vineyards1 and numerous trees2 while beyond rises the granitic plateau1 breaking off abruptly along the margin of the plain1 and deeply indented by the valleys and gorges along which the streams descend to join the ,allier4 ,but the chief point of interest is the chain of volcanic crater-cones and dome-shaped eminences which rise from the plateau1 amongst which the ,puy de ,dme towers supreme4 ,their individual forms stand out in clear and sharp relief against the western sky1 and gradually fade away towards the south into the serried masses of ,mont ,dore and ,cantal1 around whose summits the evening mists are gathering4 ,except the first view of the ,mont ,blanc range from the crest of the ,jura1 there is no scene perhaps which is calculated to impress itself more vividly on the memory than that here faintly described4#c ,illustration3 ,fig4 #ah4--,transverse view of the ,puy de ,dme and neighbouring volcanoes from the ,puy de ,chopine4--7,after ,scrope47 7b47 ,the ,vale of ,clermont4--,the plain upon which we look down was once the floor of an extensive lake1 for it is composed of various strata of sand1 clay1 marl1 and limestone1 containing various genera and species of fresh-water shells4 ,these strata are of great thickness1 perhaps a thousand feet in some places2 and along with such shells as ,paludina1 ,planorbis1 and ,limna are also found remains of various other animals1 such as fish1 serpents1 batrachians1 crocodiles1 ruminants1 and those of huge pachyderms1 as ,rhinoceros1 ,dinotherium1 and ,cnotherium4 ,this great lake1 occupying a hollow in the old granitic platform of ,central ,france1 must have been in existence for an extensive period1 which ,,mm4 ,pomel1 ,aymard1 and ,lyell all unite in referring to that of the ,lower ,miocene4 ,but what is to us of special interest is the fact that1 in the deposits of this lake of the ,haute ,loire1 with the exception of the very latest1 there is no intermixture of volcanic products such as might have been expected to occur if the neighbouring volcanoes had been in activity during its existence4 ,hence it may be supposed that1 as ,scrope suggested1 the waters of the lake were drained off owing to the disturbance in the levels of the country caused by the first explosions of the ,auvergne volcanoes4#d ,if this be so1 then we possess a key by which to determine the period of the first formation of volcanoes in ,central ,france2 for1 as the animal remains enclosed in the lacustrine deposits of the ,vale of ,clermont belong to the early ,miocene stage1 and the earliest traces of contemporaneous volcanic ejecta are found only in the uppermost deposits1 we may conclude that the first outburst of volcanic action occurred towards the close of the ,miocene period--a period remarkable for similar exhibitions of internal igneous action in other parts of the world4 7c47 ,successive ,stages of ,volcanic ,action in ,auvergne4--,the volcanic region here described1 which has an area of about one hundred square miles1 does not appear to have been at one and the same period of time the theatre of volcanic action over its whole extent4 ,on the contrary1 this action appears to have commenced at the southern border of the region in the ,cantal1 and travelling northwards1 to have broken out in the ,mont ,dore region2 finally terminating its outward manifestations among the craters and domes of the ,puy de ,dme4 ,in a similar manner the volcanic eruptions of the ,haute ,loire and ,ardche1 lying to the eastward1 and separated from those of the ,cantal by the granitoid ridge of the ,montagnes de ,margeride1 belong to two successive periods referable very closely to those of the ,mont ,dore and the ,puy de ,dme groups4#e ,the evidence in support of this view is very clear and conclusive2 for1 while the volcanic craters formed of ash1 lapilli1 and scori1 together with the rounded domes of trachytic rock of which the ,puy de ,dme group is composed1 preserve the form and surface indications of recently extinguished volcanoes1 those which we may assume to have been piled up in the region of ,mont ,dore and ,cantal have been entirely swept away by prolonged rain and river action1 and the sites of the ancient craters and cones of eruption are only to be determined by tracing the great sheets of lava up the sides of the valleys to their sources1 generally situated at the culminating points of their respective groups4 ,other points of evidence of the great antiquity of the latter groups might be adduced from the extent of the erosion which has taken place in the sheets of lava having their sources in the vents of the ,plomb du ,cantal and of ,mont ,dore1 owing to which1 magnificent valleys1 many miles in length and hundreds of feet in depth1 have been cut out of these sheets of lava and their supporting rocks1 whether granitic or lacustrine1 and the materials carried away by the streams which flow along their beds4 ,these points will be better understood when ,i come to give an account of the several groups2 and in doing so ,i will commence with that of the ,cantal4#f 7d47 ,the ,volcanoes of the ,cantal4--,the original crater-cones of this group have entirely disappeared throughout the long ages which have elapsed since the lava-streams issued forth from their internal reservoirs4 ,the general figure of this group of volcanic mountains is that of a depressed cone1 whose sides slope away in all directions from the central heights1 which are deeply eroded by streams rising near the apex and flowing downwards in all directions towards the circumference of the mountain1 where they enter the ,lot1 the ,dordogne1 and the ,allier4 ,the orifice of eruption was situated at the ,plomb du ,cantal1 formed of solid masses of trachyte1 which1 owing1 as ,mr4 ,scrope supposes1 to a high degree of fluidity1 were able to extend to great distances in extensive sheets1 and were afterwards covered by repeated and widely-spread flows of basalt2 so that the trachyte towards the margin of the volcanic area becomes less conspicuous than the basalt by which it is more or less concealed from view1 or overlapped4 ,extensive beds of tuff and breccia accompany the trachytic masses4 ,magnificent sections of the rocks are laid open to view along the sides of the valleys1 which are steep and rock-bound4 ,except towards the south-west1 about ,aurillac1 where lacustrine strata overlie the granite1 the platform from which rises the volcanic dome is composed of granitic or gneissose rocks4 ,accompanying the lava-streams are great beds of volcanic agglomerate1 which ,mr4 ,scrope considers to have been formed contemporaneously with the lava which they envelop1 and to be due to torrents of water tumultuously descending the sides of the volcano at periods of eruption1 and bearing down immense volumes of its fragmental ejecta in company with its lava-streams4#g ,nowhere throughout this region do beds of trachyte and basalt alternate with one another2 in all cases the basalt is the newer of the two varieties of rock1 and this is generally the case throughout the region here described4 7e47 ,volcanoes of ,mont ,dore4--,this mountain lies to the north of that of ,cantal1 and somewhat resembles it in general structure and configuration4 ,like ,cantal1 it is destitute of any distinct crater2 all that is left of the central focus of eruption being the solidified matter which filled the throat of the original volcano1 and which forms a rocky mass of lava1 rising in its highest point1 the ,pic de ,saucy1 to an elevation 7as given by ,ramond7 of #fbeh feet above the level of the sea1 thus exceeding that of the ,plomb du ,cantal by #abh feet4 ,its figure will be best understood by supposing seven or eight rocky summits grouped together within a circle of about a mile in diameter1 from whence1 as from the apex of an irregular and flattened cone1 all the sides slope more or less rapidly downwards1 until their inclination is gradually lost in the plain around4 ,this dome-shaped mass has been deeply eroded on opposite sides by the valleys of the ,dordogne and ,chambon2 while it is further furrowed by numerous minor streams4#h ,the great beds of volcanic rock1 disposed as above stated1 consist of prodigious layers of scori1 pumice-stones1 and detritus1 alternating with beds of trachyte and basalt1 which often descend in uninterrupted currents till they reach the granite platform1 and then spread themselves for miles around4 ,the sheets of basalt are found to stretch to greater distances than those of trachyte1 and have flowed as far as #ae or #bj miles from their orifices of eruption2 while in some cases1 on the east and north sides1 they have extended as far as #be or #cj miles from the central height4 ,on the other hand1 a radius of about ten miles from the centre would probably include all the streams of trachyte2--so much greater has been the viscosity of the basalt over the latter rock4 ,some portions of these great sheets of lava1 cut off by river valleys or eroded areas from the main mass of which they once formed a part1 are found forming isolated terraces and plateaux either on the granitic platform1 or resting on the fresh-water strata of the valley of the ,allier1 while in a northern direction they overspread a large portion of the granitic plateau from which rise the ,puy de ,dme and associated volcanic mountains4 ,still more remarkable are the cases in which these lava-streams have descended into the old river channels which drained the granitic plateau4 ,thus the current which took its origin in the ,puy ,gros descended into the valley of the ,dordogne1 while another stream invaded the gorge of ,champeix on the eastern side4 ,the more ancient lava-streams just described are invaded by currents and surmounted by cones of eruption of more recent date1 similar to those of the ,puy de ,dme group lying to the northward4 ,such cones and currents1 amongst which are the ,puy de ,tartaret and that of ,montenard1 present exactly the same characters as those of this group1 to which we shall return further on4 7f47 ,volcanoes of the ,haute ,loire and ,ardche4--,separated by the valley of the ,allier and the granitic ridge of ,la ,margeride from the volcanic regions of ,cantal and ,mont ,dore is another volcanic region of great extent1 which reaches its highest elevation in the central points of ,mont ,mezen1 attaining an elevation 7according to ,cordier7 of #ehbj feet1 and formed of clinkstone4 ,the volcanic products of ,mezen have been erupted from one central orifice of vast size1 and consist mainly of extensive sheets of clinkstone1 a variety of trachytic lava1 which have taken courses mainly towards the north-west and south-east4 ,these great sheets1 one of which appears to have covered a space more than #bf miles in length with an average breadth of #f miles1 thus overspreading an estimated area of #aef square miles1 has been deeply eroded by streams draining into the ,loire1 along whose banks the rocks tower in lofty cliffs2 while it has also suffered enormous denudation1 by which outlying fragments are disconnected from the main mass1 and form flat-topped hills and plateaux as far distant as ,roche en ,reigner and ,beauzac1 at the extreme distance 7as stated above7 of #bf miles from the source of eruption4 ,but even more remarkable than the above are the vast basaltic sheets which stretch away for a distance of #cj miles by ,privas almost to the banks of the ,rhne1 opposite ,montlimart4 ,these have their origin amongst the clinkstone heights of ,mont ,mezen1 and taking their course along the granitic plateau in a south-easterly direction1 ultimately pass over on to the ,jurassic and ,cretaceous formations composing the plateau of the ,coiron1 which break off in vertical cliffs from #cjj to #djj feet in height1 surmounting the slopes that rise from the banks of the ,ardche and ,escourtais rivers near ,villeneuve de ,bere4 ,this is probably one of the most extensive sheets of basalt with which we are acquainted in the ,european area1 and it is only a remnant of a vastly greater original sheet4#i ,illustration3 ,fig4 #ai4--,mont ,demise1 near ,le ,puy1 seen from the ,s4,e4 7,after ,scrope47--#a4 ,building standing on old breccia1 rocks of the ,col2 #b4 ,road to ,brioude2 #c4 ,croix de la ,paille2 #d4 ,orgue d',expailly 7basalt72 #e4 ,spot where human bones were found4 7g47 ,newer ,volcanoes of the ,haute ,loire 7the ,velay and ,vivarais74--,subsequently to the formation of the lava-streams above described1 and probably after the lapse of a lengthened period1 the region of the ,haute ,loire and ,ardche became the scene of a fresh outburst of volcanic action1 during which the surface of the older lavas1 or of the fundamental granite1 was covered by numerous crater-cones and lava-streams strewn along the banks of the ,allier and of the ,loire for many miles4 ,these cones and craters are not quite so fresh as those of the ,mont ,dme group2 those of the ,haute ,loire being slightly earlier in point of time1 and1 as ,daubeny shows1 belonging to a different system4 ,so numerous are these more recent cones and craters that ,scrope counted more than #aej of them1 and probably omitted many4 ,the volcanic phenomena now described have a special interest as bearing on the question whether man was an inhabitant of this region at the time of these later eruptions4 ,the question seems to be answered in the affirmative by the discovery of a human skull and several bones in the volcanic breccia of ,mont ,demise1 in company with remains of the elephant 7,e4 primigenius71 rhinoceros 7,r4 tichorhinus71 stag1 and other large mammifers4 ,the discovery of these remains was made in the year #ahdd1 and the circumstances were fully investigated and reported upon by ,m4 ,aymard1 and afterwards by ,mr4 ,poulett ,scrope1 upon whose mind no possible doubt of the fact remained4 ,from what we now know of the occurrence of human remains and works of art in other parts of ,france and ,europe1 no surprise need be felt at the occurrence of human remains in company with some extinct mammalia in these volcanic tuffs1 which belong to the ,post-,pliocene or superficial alluvia antecedent to the historic period4#aj 7h47 ,mont ,dme ,chain4--,we now come to the consideration of the most recent of all the volcanic mountain groups of the region of ,central ,france1 that of the ,puy de ,dme1 lying to the north of ,mont ,dore and ,cantal4 ,we have seen that there is almost conclusive evidence that man was a witness to the later volcanic outbursts of the ,vivarais1 and as these craters seem to be of somewhat earlier date than those of the ,puy de ,dme group1 we cannot doubt that they were in active eruption when human beings inhabited the country1 and not improbably within what is known as the ,historic ,period4 ,no mention1 however1 is made either by ,csar1 ,pliny1 or other ,roman writers of the existence of active volcanoes in this region4 ,csar1 who was a close observer1 and who carried the ,roman arms into ,auvergne1 makes no mention of such2 nor yet does the elder ,pliny1 who enumerated the known burning mountains of his day all over the ,roman ,empire4 ,it is not till we come down to the fifth century of our era that we find any notices which might lead us to infer the existence of volcanic action in ,central ,france4 ,this is the well-known letter written by ,sidonius ,apollonarius1 bishop of ,auvergne1 to ,alcinus ,avitus1 bishop of ,vienne1 in which the former refers to certain terrific terrestrial manifestations which had occurred in the diocese of the latter4 ,but1 as ,dr4 ,daubeny observes1 this is no evidence of volcanic action in ,auvergne1 where ,sidonius himself resided2 the terrestrial disturbances above referred to may have been earthquake shocks of extreme severity4#aa ,but although we have no reliably historical record of volcanic action amongst the mountains of the ,mont ,dme group1 the fact that these are1 comparatively1 extremely recent will be evident to an observer visiting this district1 and this conclusion is based on three principal grounds3 first1 because of the well-preserved forms of the original craters1 though generally composed of very loose material1 such as ashes1 lapilli1 and slag2 secondly1 because of the freshness of the lava-streams over whose rugged surfaces even a scanty herbage has in some places scarcely found a footing2#ab and thirdly1 because the lava from the crater-cones has invaded channels previously occupied by the earlier lavas1 or those which had been eroded since the overflow of the great basaltic sheets of ,mont ,dore4 ,still1 as in the case of the valleys of ,lake ,aidot1 of ,channonat1 and of ,royat1 these streams are sufficiently ancient to have given time for the existing rivers to have worn out in them channels of some depth1 but bearing no comparison to the great valleys which had been eroded out of the more ancient lavas1 such as those of the ,coiron1 of the ,ardche1 and of the ,dordogne and ,chambon in the district of ,mont ,dore4 7i47 ,dome-shaped ,volcanic ,hills4--,i have previously 7page #ae7 referred to the two classes of volcanic eminences to be found in the chain of the ,puy de ,dme2 one indicated by the name itself1 formed of a variety of trachytic lava called domite1 and of the form of a dome2 the other1 composed of fragmental matter piled up in the form of a crater or cup1 often ruptured on one side by a stream of lava which has burst through the side1 owing to its superior density4 ,of the former class the ,puy de ,dme and the ,grand ,sarcoui 7see ,fig4 #ah7 are the most striking examples out of the five enumerated by ,scrope1 while there is a large number1 altogether sixty-one1 belonging to the latter class4 ,these domes and crater-cones1 as already stated1 rise from a platform of granite1 either directly or from one formed of the lava-sheets of the ,mont ,dore region1 which in turn overlies the granitic platform4 ,of the nearly perfect craters there are the ,petit ,puy de ,dme1 lying partially against the northern flank of the greater eminence2 the ,puy de ,cone1 remarkable for the symmetry of its conical form1 rising to a height of #ijj feet from the plain2 and the ,puys de ,chaumont and ,thiolet lying to the north of the ,puy de ,dme4 ,of those to the south of this mount1 two out of the three craters of the ,puy de ,barme and the ,puy de ,vichatel are perfect2 but most of the crater-cones south of the ,puy de ,dme are breached4 ,some of the lava streams by which these craters were broken down flowed for long distances4 ,that the lava followed the showers of ashes and lapilli forming the walls of the craters is rendered very evident in the case of the ,puy de la ,vache1 whose lava-stream coalescing with those from the ,puy de la ,solas and ,puy ,noir1 deluged the surrounding tracts and flowed down the ,channonat ,valley as far as ,la ,roche ,blanc in the ,vale of ,clermont4 ,in the interior of the upper part of the crater still remaining may be seen the level 7so to speak7 to which the molten lava rose before it burst its barrier4 ,this level is marked by a projecting platform of reddish or yellow material1 rich in specular iron1 apparently part of the frothy scum which formed on the surface of the lava and adhered to the side of the basin at the moment of its being emptied4 ,space does not permit a fuller description of this remarkable assemblage of extinct volcanoes1 and the reader must be referred for further details to the work of ,mr4 ,scrope4 ,i shall content myself with some further reference to the central figure in this grand chain1 the ,puy de ,dme itself4 ,ascent of the ,puy de ,dme4--,on ascending by the winding path up the steep side of the mount1 and on reaching the somewhat flattened summit1 the first objects which strike the eye are the massive foundations of the ,roman temple of ,mercury2 they are hewn out of solid grey lava1 altogether different from the rock of the ,puy de ,dme itself1 which must have been obtained from one of the lava-sheets of the ,mont ,dore group4 ,to have carried these large blocks to their present resting-place must have cost no little labour and effort4 ,the temple is supposed to have been surmounted by a colossal statue of the winged deity1 visible from all parts of the surrounding country which was dedicated to his honour1 and the foundations were only discovered a few years ago when excavating for the foundation of the observatory1 which stands a little further on under the charge of ,professor ,janssen4 ,on proceeding to the northern crest of the platform a wonderful view of the extinct craters and domes--about forty in number1 and terminating in the ,puy de ,beauny1 the most northerly member of the chain--is presented to the spectator4 ,to the right is the ,vale of ,clermont and the rich valley of the ,allier merging into the great plain of ,central ,france4 ,on the south side of the platform a no less remarkable spectacle meets the eye4 ,the chain of ,puys and broken craters stretches away southwards for a distance of nearly ten miles1 while the horizon is bounded in that direction by the lofty masses of the ,mont ,dore1 ,cantal1 and ,le ,puy ranges4 ,nor does it require much effort of the imagination to restore the character of the region when these now dormant volcanoes were in full activity1 projecting showers of ashes and stones high into the air amidst flames of fire and vast clouds of incandescent gas and steam4 ,the material of which the ,puy de ,dme is formed consists of a light grey1 nearly white1 soft felsitic lava1 containing crystals of mica1 hornblende1 and specular iron-ore4 ,it is highly vesicular1 and was probably extruded in a pasty condition from a throat piercing the granitic plateau and the overlying sheet of ancient lava of ,mont ,dore4 ,it has been suggested that such highly felsitic and acid lavas as that of which the ,puy de ,dme1 the ,grand ,sarcoui1 and ,cliersou are composed1 may have had their origin in the granite itself1 melted and rendered viscous by intense heat4 ,dr4 ,e4 ,gordon ,hull has suggested that the domite hills 7owing to their low specific gravity7 may have filled up pre-existing craters of ashes and scori without rupturing them1 as in the case of the heavier basaltic lavas1 and then still continuing to be extruded1 may have entirely enveloped them in its mass2 so that each domite hill encloses within its interior a crater formed of ashes1 stones1 and scori4 ,in the case of the ,puy de ,dme there is some evidence that the domite matter rests on a basis of ashes and scori1 which may be seen in a few places around the base of the cone4 ,it is difficult without some such theory as this to explain how a viscous mass was able to raise mountains some #bjjj or #cjjj feet above the surrounding plain4#ac 7j47 ,sketch of the ,volcanic ,history of ,central ,france4--,it now only remains to give a brief resum of the volcanic history of this region as it may be gathered from the relations of the rocks and strata to the volcanic products1 and of these latter to each other4 #ast ,stage4--,it would appear that at the close of the ,eocene period great terrestrial changes occurred4 ,the bed of the sea was converted into dry land1 the strata were flexured and denuded1 and a depression was formed in the granitic floor of ,central ,france1 which1 in the succeeding ,miocene period1 was converted into an extensive lake peopled by molluscs1 fishes1 reptiles1 and pachyderms of the period4 #bnd ,stage4--,towards the close of the ,miocene epoch volcanic eruptions commenced on a grand scale over the granitic platform in the districts now called ,mont ,dore1 ,cantal1 and the ,vivarais4 ,vast sheets of trachytic and basaltic lavas successively invaded the tracts surrounding the central orifices of eruption1 now constituting the more ancient of the lava-sheets of the ,auvergne region1 and1 invading the waters of the neighbouring lake1 overspread the lacustrine deposits which were being accumulated therein4 ,these volcanic eruptions probably continued throughout the ,pliocene period1 interrupted by occasional intervals of inactivity1 and ultimately altogether ceased4 #crd ,stage4--,towards the close of the ,pliocene period terrestrial movements took place1 owing to which the waters of the lake began to fall away1 and the sheets of lava were subjected to great denudation4 ,this process1 probably accelerated by excessive rainfall during the succeeding ,post-,pliocene and ,pluvial periods1 was continued until plains and extensive river-valleys were eroded out of the sheets of lava and their supporting granitic rocks and the adjoining lacustrine strata4 #dth ,stage4--,a new outburst of volcanic forces marks this stage1 during which the chain of the ,puy de ,dme was thrown up on the west1 and that of the newer cones of the ,vivarais on the south-east of the lacustrine tract4 ,the waters of the lake were now completely drained away through the channel of the ,allier1 and denudation1 extending down to the present day1 began over the area now forming the ,vale of ,clermont and adjoining districts4 ,the volcanic action ultimately spent its force2 and somewhere about the time of the appearance of man1 the mammoth1 rhinoceros1 stag1 and reindeer on the scene1 eruptions entirely ceased1 and gradually the region assumed those conditions of repose by which it is now physically characterised4 #a ,the literature referring to this region is very extensive4 ,guettard in #agge1 afterwards ,faujas1 published descriptions of the rocks of the ,vivarais and ,velay2 and ,desmarest's geological map1 published in #aggi1 is a work of great merit4 ,the district was afterwards described by ,daubeny1 ,lyell1 ,von ,buch1 and others2 but by far the most complete work is that of ,scrope1 entitled ,volcanoes of ,central ,france1 containing maps and numerous illustrations1 published in #ahbf1 and republished in a more extended form in #aheh2 to this ,i am largely indebted4 #b ,a monument to ,pascal1 erected by the citizens1 occupies the centre of the square in ,clermont4 ,it will be remembered that ,pascal verified the conclusions arrived at by ,torricelli regarding the pressure of the atmosphere1 by carrying a ,torricellian tube to the summit of the ,puy de ,dme1 and recording how the mercury continually fell during the ascent1 and rose as he descended4 ,this experiment was made in #afde4 #c ,in this visit to ,auvergne in the summer of #ahhj1 the author was accompanied by his son1 ,dr4 ,e4 ,gordon ,hull1 and ,sir ,robert ,s4 ,ball4 ,on reaching the station at the summit of the ridge it seemed as if the volcanic fires had again been lighted1 for the whole sky was aglow with the rays of the western sun4 #d ,on the other hand1 certain beds of ash and other volcanic ejecta occur in the uppermost strata of lake deposits of ,limagne1 so that these may indicate the commencement of the period of eruption1 as suggested further on4 #e ,only very closely2 for ,mr4 ,scrope considers that the crater-cones of the chain of the ,haute ,loire give evidence of a somewhat earlier epoch of activity than those of the ,puy de ,dme1 as they have undergone a greater amount of subaerial erosion4 #f ,the extent of this river erosion has been clearly brought out by ,scrope1 and is admirably illustrated by several of his panoramic views1 such as that in ,plate ,,ix4 of his work4 #g ,scrope1 loc4 cit41 p4 #adg4 #h ,scrope1 loc4 cit41 p4 #add4 #i ,scrope gives a view of these remarkable basaltic cliffs in ,plate ,,xii4 of his work1 from which the above account is taken4 ,at one spot near the village of ,le ,gua there is a break in the continuity of the sheet4 #aj ,see ,scrope1 loc4 cit41 p4 #aha2 also ,appendix1 p4 #bbh4 ,while there is no prim facie reason for questioning the origin of the ,demise skull1 yet from what ,lyell states in his ,antiquity of ,man1 p4 #aif1 it will be seen that he found it impossible to identify its position1 or to determine beyond question that its interment was due to natural causes4 ,but assuming this to be the case1 he shows how the individual to whom it belonged might have been enveloped in volcanic tuff or mud showered down during the final eruption of the volcano of ,demise4 ,,mm4 ,hbert and ,lartet1 on visiting the locality1 also failed to find in situ any exact counterpart of the stone now in the museum of ,le ,puy4 #aa ,see ,daubeny1 ,volcanoes1 p4 #ca4 #ab ,that is to say1 the surfaces of the lava-streams are not at all1 or only slightly1 decomposed into soil suitable for the growth of plants1 except in rare instances4 #ac ,e4 ,g4 ,hull1 ,on the ,domite ,mountains of ,central ,france1 ,scien4 ,proc4 ,roy4 ,dublin ,society1 ,july #ahha1 p4 #ade4 ,dr4 ,hull determined the density of the domite of the ,puy de ,dme to be #b4e1 while that of lava is about #c4j4 ,,chapter ,,vii4 ,,the ,,volcanic ,,district ,,of ,,the ,,rhine ,,valley4 ,the region bordering the ,rhine along both its banks above ,bonn1 and extending thence along the valley of the ,moselle and into the ,eifel1 has been the theatre of active volcanic phenomena down into recent times1 but at the present day the volcanoes are dormant or extinct4 7a47 ,geological ,structure4--,the fundamental rocks of this region belong to the ,silurian1 ,devonian1 and ,carboniferous systems1 consisting of schists1 grits1 and limestones1 with occasional horizontal beds of ,miocene sandstone and shale with lignite1 resting on the upturned edges of the older rocks4 ,scattered over the greater part of the district here referred to are a number of conical eminences1 often with craters1 the bottoms of which are usually sunk much below the present level of the country1 and thus receiving the surface drainage1 have been converted into little lakes called maars1 differing from ordinary lakes by their circular form and the absence of any apparent outlet for their waters4#a ,but before entering into details1 it may be desirable to present the reader with a short outline of the physical history of the region 7which has been ably done by ,dr4 ,hibbert in his treatise1 to which ,i have already referred71 so as to enable him better to understand the succession of physical events in its volcanic history4 ,illustration3 ,fig4 #bj4--,sketch ,map to show the physical condition of the ,rhenish area in the ,miocene epoch4--7,after ,hibbert47 7b47 ,physical ,history4--,from the wide distribution of stratified deposits of sand and clay at high levels on both banks of the ,rhine north of the ,moselle1 it would appear that an extensive fresh-water basin1 which ,dr4 ,hibbert calls ,the ,basin of ,neuwied1 occupied a considerable tract on both banks1 in the centre of which the present city of ,neuwied stands4 ,this basin was bounded towards the south by the slopes of the ,hndsruck and ,taunus1 which at the time here referred to formed a continuous chain of mountains4 7,fig4 #bj47 ,to the south of this chain lay the ,tertiary basin of ,mayence1 which was connected at an early period--that of the ,miocene--with the waters of the ocean1 as shown by the fact that the lower strata contain marine shells2 these afterwards gave place to fresh-water conditions4 ,the basin of ,neuwied was bounded towards the north by a ridge of ,devonian strata which extended across the present gorge of the ,rhine between ,andernach and ,linz1 and to the north of this barrier lay another more extensive fresh-water basin1 that of ,cologne4 ,from this it will be seen that the ,rhine1 as we now find it1 had then only an infantile existence2 in fact1 its waters to the south of the ,hndsruck ridge drained away towards the south4 ,but towards the commencement of the ,pliocene period the barriers of the ,hndsruck and ,taunus1 as also that of the ,linz1 were broken through1 and the course of the waters was changed2 and thus gradually1 as the river deepened its bed1 the waters were drained off from the great lakes4#b ,this rupture of the barriers may have been due1 in the first instance1 to the terrestrial disturbances accompanying the volcanic eruptions of the ,eifel and ,siebengebirge1 though the erosion of the gorges at ,bingen and at ,linz to their present depth and dimensions is of course due to prolonged river action4 ,it was about the epoch we have now arrived at--viz41 the close of the ,miocene--that volcanic action burst forth in the region of the ,lower ,rhine4 ,it is probable that this action commenced in the district of the ,siebengebirge1 and afterwards extended into that of the ,moselle and the ,eifel1 the volcanoes of which bear evidence of recent date4 ,layers of trachytic tuff are interstratified with the deposits of sand1 clay1 and lignite of the formation known as that of the ,brown ,coal--of ,miocene age--which underlies nearly the whole of the volcanic district on both sides of the ,rhine near ,bonn1#c thus showing that volcanic action had already commenced in that part to some extent2 but it does not appear from ,dr4 ,hibbert's statement that any such fragments of eruptive rock are to be found in the strata which were deposited over the floor of the ,neuwied basin4#d ,it will be recollected that the epoch assigned for the earliest volcanic eruptions of ,auvergne was that here inferred for those of the ,lower ,rhine--viz41 the close of the ,miocene stage--and from evidence subsequently to be adduced from other ,european districts1 it will be found that there was a very widely spread outburst of volcanic action at this epoch4 7c47 ,the ,range of the ,siebengebirge4--,this range of hills--formed of the older volcanic rocks of the ,lower ,rhine--rises along the right bank of this noble river opposite ,bonn1 where it leaves the narrow gorge which it traverses all the way from ,bingen1 and opens out on the broad plain of ,northern ,germany4 ,the range consists of a succession of conical hills sometimes flat-topped--as in the case of ,petersberg2 and at the ,drachenfels1 near the centre of the range it presents to the river a bold front of precipitous cliffs of trachyte porphyry4 ,the sketch 7,fig4 #ba7 here presented was taken by the author in #aheg from the old extinct volcano of ,roderberg1 and will convey1 perhaps1 a better idea of the character of this picturesque range than a description4 ,the ,siebengebirge1 although appearing as an isolated group of hills1 is in reality an offshoot from the range of the ,westerwald1 which is connected with another volcanic district of ,central ,germany known as the ,vogelsgebirge4 ,the highest point in the range is attained in the ,lohrberg1 which rises #acee feet above the sea2 the next1 the ,great ,trnkeberg1 #accj feet2 and the next1 ,great ,oelberg1 #abif feet4 ,illustration3 ,fig4 #ba4--,the ,volcanic ,range of the ,siebengebirge1 seen from the left bank of the ,rhine1 above ,bonn4--7,original47 ,the range consists mainly of trachytic rocks--namely1 trachyte-conglomerate1 and solid trachyte1 of which ,h4 von ,dechen makes two varieties--that of the ,drachenfels1 and that of the ,wolkenburg4 ,but associated with these highly-silicated varieties of lava--and generally1 if not always1 of later date--are basaltic rocks which cap the hills of ,petersberg1 ,nonnenstrom1 ,gr4 and ,ll4 ,oelberg1 ,gr4 ,weilberg1 and ,ober ,dollendorfer ,hardt4 ,the question whether there is a transition from the one variety of volcanic rock into the other1 or whether each belongs to a distinct and separate epoch of eruption1 does not seem to be very clearly determined4 ,mr4 ,leonard ,horner states that it would be easy to form a suite of specimens showing a gradation from a white trachyte to a black basalt2#e but we must recollect that when ,mr4 ,horner wrote1 the microscopic examination of rocks by means of thin sections was not known or practised1 and an examination by this process might have proved that this apparent transition is unreal4 ,according to ,h4 von ,dechen1 there are sheets of basalt older than the greater mass of the brown coal formation1 and others newer than the trachyte2#f while dykes of basalt traversing the trachytic lavas are not uncommon4#g ,the trachyte-conglomerate--which seems to be associated with the upper beds of the brown coal strata--is traversed by dykes of trachyte of later date2 and though it is difficult to trace the line between the two varieties of this rock on the ground1 ,dr4 von ,rath has recognised the general distinction between them1 which consists in the greater abundance of hornblende and mica in the trachyte of the ,wolkenburg than in that of the ,drachenfels4 ,the trachyte of the ,drachenfels was probably the neck of a volcano which burst through the fundamental schists of the ,devonian period4 ,it is remarkable for the large crystals of sanidine 7glassy felspar7 which it contains1 and has a rude columnar structure4 ,the absence of any clearly-defined craters of eruption1 such as are to be found in the ,eifel district and on the left bank of the ,rhine--as1 for example1 in the case of the ,roderberg--may be regarded as sufficient evidence that this range is of comparatively high antiquity4 ,it seems to bear the same relation to the more modern craters of the ,eifel and ,moselle that the ,mont ,dore and ,cantal volcanoes do to those of the ,puy de ,dme4 ,in both cases1 denudation carried on throughout perhaps the ,pliocene and ,post-,pliocene periods down to the present day has had the effect of demolishing the original craters2 so that what we now observe as forming these ranges are the consolidated columns of original molten matter which filled the throats of the old volcanoes1 or the sheets of lava which were extruded from them1 but are now probably much reduced in size and extent4 ,having thus given a description of the older volcanic range on the right bank of the ,rhine1 we shall cross the river in search of some details regarding the more recent group of ,rhenish volcanoes1 commencing with that of the ,roderberg1 a remarkable hill a few miles south of ,bonn1 from which the view of the ,seven ,mountains was taken4 ,illustration3 ,fig4 #bb4--,section of the extinct crater of the ,roderberg on the bank of the ,rhine1 above ,bonn4--7,original47 7d47 ,the ,roderberg4--,this crater1 which was visited by the author in #aheg1 is about one-fourth of a mile in diameter1 and is in the form of a cup with gentle slopes on all sides4 ,in its centre is a farmhouse surrounded by corn-fields4 ,the general section through the hill is represented above 7,fig4 #bb74 ,the flanks on the north side are composed of loose quartzose gravel 7gerolle71 a remnant of the deposits formed around the margin of the ,basin of ,neuwied described above 7p4 #aad74 ,this gravel is found covering the terraces of the brown coal formation several hundred feet above the ,rhine4 ,besides quartz-pebbles1 the deposit contains others of slate1 grit1 and volcanic rock4 ,on reaching the edge of the crater we find the gravel covered over by black and purple scoria or slag the superposition of the scoria on the gravel being visible in several places1 showing that the former is of more recent origin4 ,on the opposite side of the crater1 overlooking the ,rhine1 we find the cliff of ,rolandsec composed of hard vesicular lava1 rudely prismatic1 and extending from the summit of the hill to its base1 about #bej feet below4 ,this is the most northerly of the group of the ,eifel volcanoes4 7e47 ,district of the ,rivers ,brhl and ,nette4--,the volcanic region of the ,lower ,eifel1 drained by these two principal streams which flow into the ,rhine1 will amply repay exploration by the student of volcanic phenomena1 owing to the variety of forms and conditions under which these present themselves within a small space4 ,the fundamental rock is slate or grit of ,devonian age1 furrowed by numerous valleys1 often richly wooded1 and diversified by conical hills of trachyte2 or by crater-cones1 formed of basalt or ashes1 sometimes ruptured on one side1 and occasionally sending forth streams of lava1 as in the cases of the ,perlinkopf1 the ,bausenberg1 and the ,engelerkopf4 ,the district attains its greatest altitude in the ,high ,acht 7,der ,hohe ,acht71 an isolated cone of slate capped by basalt with olivine1 and reaching a level of #bdcd ,rhenish feet4#h 7f47 ,the ,laacher ,see4--,it would be impossible in a work of this kind to attempt a detailed description of the ,eifel volcanoes1 often of a very complex character and obscure physical history1 as in the case of the basin of ,rieden1 where tufaceous deposits1 trachytic and basaltic lavas and crater-cones1 are confusedly intermingled1 so that ,i shall confine my remarks to the deservedly famous district of the ,laacher ,see1 which ,i had an opportunity of personally visiting some years since4#i ,illustration3 ,fig4 #bc4--,plan and ,section of the ,laacher ,see1 a lake on the borders of the ,eifel1 occupying the crater of an old volcano4--,g4 ,gravel and volcanic sand forming banks of the lake and rim of old crater2 ,l4 ,sheet of trachytic lava with columnar structure2 ,b4 ,basaltic dyke2 ,s4 ,devonian slate1 etc4 ,the ,laacher ,see is a lake of an oval form1 over an ,english mile in the shorter diameter1 and surrounded by high banks of volcanic sand1 gravel1 and scori1 except on the east side1 where cliffs of clay-slate1 in a nearly vertical position1 and striking nearly ,e4,w41 may be observed4 ,its depth from the surface of the water is #bad feet4#aj ,the ashes of the encircling banks contain blocks of slate and lava which have been torn from the sides of the orifice or neck of the volcano and blown into the air2 and there can be no doubt that the ashes and volcanic gravel is the result of very recent eruptions4 ,at the east side of the lake we find a stream of scoriaceous lava of a purple or reddish colour1 highly vesicular1 and containing crystals of mica2 but the most important lava-stream is that which has taken a southerly direction from the crater of the ,laacher ,see towards ,nieder ,mendig and ,mayen1 for a distance of about six miles4 ,this great stream is covered throughout half its distance by beds of volcanic ash and lapilli1 but emerges into the air at a distance of about two miles from the edge of the crater 7see ,fig4 #bc71 and was formerly extensively quarried in underground caverns for millstones4 ,here the rock is a vesicular trachyte1 of a greyish colour1 solidified in vertical columns of hexagonal form1 about four feet in diameter1 and traversed by transverse joint planes4 ,these quarries have been worked from the time of the ,roman occupation of the country2 and1 before the introduction of iron or steel rollers for grinding corn1 millstones were exported to all parts of ,europe and the ,british ,isles from this quarry4#aa ,the district around the ,laacher ,see is covered by laminated ejecta of the old volcano1 probably of subarial origin1 through which bosses of the fundamental slate peer up at intervals1 while the surface is diversified by several truncated cones4 7g47 ,trass of the ,brhl ,valley4--,the ,brhl ,valley1 which unites with that of the ,rhine at the town of that name1 and drains the northern side of the volcanic region1 has always been regarded with much interest by travellers for the presence of a deposit of trass with which it is partially filled4 ,the origin of this valley was pre-volcanic1 as it is hewn out of the slaty rocks of the district4 ,but at a later period it became filled with volcanic mud 7tuffstein71 out of which the stream has made for itself a fresh channel4 ,the source of this mud is considered by ,hibbert#ab to have been the old volcano of the ,lummerfeld1 which1 after becoming dormant1 was filled with water1 and thus became a lake4 ,at a subsequent period1 however1 a fresh eruption took place near the edge of the lake1 resulting in the remarkable ruptured crater known as the ,kunkskpfe1 which rises about four miles to the north of the ,laacher ,see4 ,the eruptions of this volcano appear to have displaced the mud of the ,lummerfeld1 causing it to flow down into the deep gorge of the ,brhl1 which it completely filled1 as stated above4 ,on walking down the valley one may sometimes see the junction of the tuff with the slate-rock which enfolds it4 ,the tuff consists of white felspathic mud1 with fragments of slate and lava1 reaching a depth in some places of #aej feet4 ,after it has been quarried it is ground in mills1 and used for cement stone under the name of trass4 ,it is said to resemble the volcanic mud by which ,herculaneum was overwhelmed during the first eruption of ,vesuvius1 and which was produced by the torrents of rain mixing with the ashes as they were blown out of the volcano4 ,sufficient has probably now been written regarding the dormant1 or recently extinct1 volcanic districts of ,europe to give the reader a clear idea regarding their nature and physical structure4 ,other districts might be added1 such as those of ,central ,germany1 ,hungary1 ,transylvania1 and ,styria2 but to do so would be to exceed the proposed limits of this work2 and we may therefore pass on to the consideration of the volcanic region of ,syria and ,palestine1 which adjoins the ,mediterranean district we have considered in a former page4 #a ,daubeny1 loc4 cit41 p4 #ga4 ,the geology of this region has had many investigators1 of whom the chief are ,steininger1 ,erloschenen ,vulkane in der ,eifel 7#ahbj72 ,hibbert1 ,extinct ,volcanoes of the ,basin of ,neuwied1 #ahcb2 ,nggerath1 ,das ,gebirge im ,rheinland1 etc41 #d vols42 ,horner1 ,on the ,geology of ,bonn1 ,transactions of the ,geological ,society1 ,london1 vol4 iv4 #b ,the views of ,dr4 ,hibbert are not inconsistent with those of the late ,sir ,a4 ,ramsay1 on ,the ,physical ,history of the ,valley of the ,rhine1 ,quart4 ,jour4 ,geol4 ,soc41 vol4 xxx4 7#ahgd74 #c ,von ,dechen1 ,geog4 ,beschreib4 des ,siebengebirges am ,rhein 7,bonn1 #aheb74 #d ,hibbert1 loc4 cit41 p4 #ah4 #e ,horner1 ,geology of ,environs of ,bonn1 ,transactions of the ,geological ,society1 vol4 iv41 new series4 #f ,h4 von ,dechen1 ,geog4 ,fhrer in das ,siebengebirge am ,rhein 7,bonn1 #ahfa74 #g ,ibid41 p4 #aia4 #h ,dr4 ,hibbert's work is illustrated by very carefully drawn and accurate views of some of the old cones and craters of this district1 accompanied by detailed descriptions4 #i ,the lava of ,schorenberg1 near ,rieden1 is interesting from the fact1 stated by ,zirkel1 that it contains leucite1 nosean1 and nephelin4--,die ,mikros4 ,beschaf4 d4 ,miner4 u4 ,gesteine1 p4 #aed 7#ahgc74 #aj ,hibbert1 loc4 cit41 p4 #bc4 #aa ,at the time of the author's visit the underground caverns1 which are deliciously cool in summer1 were used for the storage of the celebrated beer brewed by the ,moravians of ,neuwied4 #ab ,hibbert1 loc4 cit41 p4 #abi4 ,,part ,,iii4 ,,dormant ,,or ,,moribund ,,volcanoes ,,of ,,other ,,parts ,,of ,,the ,,world4 ,,chapter ,i4 ,,dormant ,,volcanoes ,,of ,,palestine ,,and ,,arabia4 7a47 ,region east of the ,jordan and ,dead ,sea4--,the remarkable line of country lying along the valley of the ,jordan1 and extending into the great ,arabian ,desert1 has been the seat of extensive volcanic action in prehistoric times4 ,the specially volcanic region seems to be bounded by the depression of the ,jordan1 the ,dead ,sea1 and the ,arabah as far south as the ,gulf of ,akabah2 for1 although ,safed1 lying at the head of the ,sea of ,galilee on the west of the ,jordan valley1 is built on a basaltic sheet1 and is in proximity to an extinct crater1 its position is exceptional to the general arrangement of the volcanic products which may be traced at intervals from the base of ,hermon into ,central ,arabia1 a distance of about #ajjj miles4#a ,the tract referred to has been described at intervals by several authors1 of whom ,g4 ,schumacher1#b ,l4 ,lartet1#c ,canon ,tristram1#d ,m4 ,niebuhr1#e and ,c4 ,m4 ,doughty#f may be specially mentioned in this connection4 ,the most extensive manifestations of volcanic energy throughout this long tract of country appear to be concentrated at its extreme limits4 ,at the northern extremity the generally wild and rugged tract of the ,jauln and ,haurn1 called in the ,bible ,trachonitis1 and still farther to the eastward the plateau of the ,lejah1 with its row of volcanic peaks sloping down to the vast level of ,bashan1 is covered throughout nearly its whole extent by great sheets of basaltic lava1 above which rise at intervals1 and in very perfect form1 the old crater-cones of eruption4 ,a similar group of extinct craters with lava-flows has been described and figured by a recent traveller1 ,mr4 ,c4 ,m4 ,doughty1 in parts of ,central ,arabia4 ,the general resemblance of these ,arabian volcanoes to those of the ,jauln is unquestionable2 and as they are connected with each other by sheets of basaltic lava at intervals throughout the land of ,moab1 it is tolerably certain that the volcanoes lying at either end of the chain belong to one system1 and were contemporaneously in a state of activity4 7b47 ,geological ,conditions4--,before entering any further into particulars regarding the volcanic phenomena of this region1 it may be desirable to give a short account of its geological structure1 and the physical conditions amongst which the igneous eruptions were developed4 ,down to the close of the ,eocene period the whole region now under consideration was occupied by the waters of the ocean4 ,the mountains of ,sinai were islands in this ocean1 which had a very wide range over parts of ,asia1 ,africa1 and ,europe4 ,but at the commencement of the succeeding ,miocene stage the crust was subjected to lateral contraction1 owing to which the ocean bed was upraised4 ,the strata were flexured1 folded1 and often faulted and fissured along lines ranging north and south1 the great fault of the ,jordan-,arabah valley being the most important4 ,at this period the mountains of the ,lebanon1 the table-lands of ,juda and of ,arabia1 formed of limestone1 previously constituting the bed of the ocean during the ,eocene and ,cretaceous periods1 were converted into land surfaces4 ,along with this upheaval of the sea-bed there was extensive denudation and erosion of the strata1 so that valleys were eroded over the subarial tracts1 and the ,jordan-,arabah valley received its primary form and outline4 ,up to this time there does not appear to have been any outbreak of volcanic forces2 but with the succeeding ,pliocene period these came into play1 and eruptions of basaltic lava took place along rents and fissures in the strata1 while craters and cones of slag1 scori1 and ashes were thrown up over the region lying to the east of the ,sea of ,galilee and the sources of the ,jordan on the one hand1 and the central parts of the great ,arabian ,desert on the other4 ,these eruptions1 probably intermittent1 continued into the succeeding ,glacial or ,pluvial period1 and only died out about the time that the earliest inhabitants appeared on the scene4 7c47 ,the ,jauln and ,haurn4--,this tract is bounded by the valley of the ,jordan and the ,sea of ,galilee on the west1 from which it rises by steep and rocky declivities into an elevated table-land1 drained by the ,yarmk 7,hieromax71 the ,nahr er ,rukkd1 and other streams1 which flow westwards into the ,jordan along deep channels in which the basaltic sheets and underlying limestone strata are well laid open to view4 ,on consideration it seems improbable that the great sheets of augitic lava1 such as cover the surface of the land of ,bashan1 are altogether the product of the volcanic mountains which appear to be confined to special districts in this wide area4 ,some of the craters do indeed send forth visible lava-streams1 but they are insignificant as compared with the general mass of the plateau-basalts2 and the crater-cones themselves appear in some cases to be posterior to the platforms of basalt from which they rise4 ,it is very probable1 therefore1 that the lavas of this region have1 in the main1 been extruded from fissures of eruption at an early period1 and spread over the surface of the country in the same manner as those of the ,snake ,river region1 and the borders of the ,pacific ,ocean of ,north ,america1 and possibly of the ,antrim ,plateau in ,ireland1 afterwards to be described4 ,the volcanic hills which rise above the plateau are described in detail by ,schumacher4 ,of these1 ,tell ,ab ,nedr is the largest in the ,jauln4 ,it reaches an elevation of #dacb feet above the ,mediterranean ,sea1 and #agaj feet above the plain from which it rises2 the circumference of its base is three miles1 and the rim of the crater itself1 which is oval in form1 is #acca yards in its larger diameter4 ,the interior is cultivated by ,circassians1 and is very fruitful2 the walls descend at an angle of about #cj on the inside1 the exterior slope of the mountain being about #bb4 ,the cone seems to be formed chiefly of scori1 and the lava-stream1 which issues forth from the interior1 forms a frightfully stony and lacerated district4#g ,illustration3 ,fig4 #bd4--;,extinct ,craters in the ,jauln1 north-east from the ,sea of ,galilee1 called ,tell ,ab en ,ned and ,tell el ,urm1 with a central cone4--7,after ,schumacher47 ,another remarkable volcano is the ,tell ,ab en ,ned 7,fig4 #bd74 ,this is a double crater1 with a cone 7probably of cinders7 rising from the interior of one of them4 ,the highest point of the rim of one of the craters reaches a level of #djdb feet above the sea4 ,a lava-stream issues forth from ,ab en ,ned1 and unites with another from a neighbouring volcano4 ,tell el ,ahmr is a ruptured crater of imposing aspect1 reaching an elevation of #djfj feet1 and sending forth a lava-current1 which falls in regular terraces from the outlet towards the west and north4 ,the ruptured crater of ,tell el ,akkasheh1 which reaches a height of #cdjj feet1 has a less forbidding aspect than the greater number of the extinct volcanoes of this region1 owing to the fact that its sides are covered by oaks1 which attain to magnificent proportions along the summit4 ,numerous other volcanic hills occur in this district1 but the most remarkable is that called ,tell el ,farras 7the ,hill of the ,horse74 ,it is an isolated mountain1 visible from afar1 and reaches an elevation of #caaj feet1 or nearly #hjj feet above the surrounding plain4 ,the oval crater of this volcano opens towards the north1 and has a depth of #ajh feet below the edge1 with moderately steep sloping sides 7#ag-cb71 while the slope of the exterior1 at first steep1 gradually lessens to #bj-ba4 ,these slopes are covered with reddish or yellowish slag4 ,the above examples will probably suffice to afford the reader a general idea of the size and form of the volcanoes in this little known region4 ,it has been stated above that the great lava-floods have probably been poured forth intermittently4 ,the statement receives confirmation from the observations of ,canon ,tristram1 made in the valley of the ,yarmk4#h ,this impetuous torrent rushes down a gorge1 sometimes having limestone on one side and a wall of basalt on the other4 ,this is due to the fact that the river channel had been eroded before the volcanic eruptions had commenced2 but on the lava-stream reaching the channel1 it naturally descended towards the valley of the ,jordan along its bed1 displacing the river1 or converting it into clouds of steam4 ,subsequently the river again hewed out its channel1 sometimes in the lava1 sometimes between this rock and the chalky limestone4 ,but1 in addition to this1 it has been observed that there is a bed of river gravel interposed between two sheets of basalt in the ,yarmk ravine2 showing that after the first flow of that molten rock the river reoccupied its channel1 which was afterwards invaded by another molten lava-stream1 into which the waters have again furrowed the channel which they now occupy4 ,the basaltic sheets descend under the waters of the ,sea of ,galilee on the east side1 and were probably connected with those of ,safed1 crossing the ,jordan valley north of that lake2 owing to this the waters of the ,lake of ,merom 7,huleh7 were pent up1 and formerly covered an extensive tract1 now formed of alluvial deposits4 7d47 ,land of ,moab4--,proceeding southwards into the ,land of ,moab1 the volcanic phenomena are here of great interest4 ,extensive sheets of basaltic lava1 described as far back as #ahjg by ,seetzen1 and more recently by ,lartet and ,tristram1 are found at intervals between the ,wdies ,mojib 7,arnon7 and ,haidan4 ,on either side of the ,mojib1 cliffs of columnar basalt are seen capping the beds of white ,cretaceous limestone1 while a large mass has descended into the ,w4 ,haidan between cliffs of limestone and marl on either hand4 ,around ,jebel ,attarus--a dome-shaped hill of limestone--a sheet of basaltic lava has been poured1 and has descended the deep gorge of the ,zerka ,man1 which enters the ,dead ,sea some #bjjj feet below4 ,this gorge had been eroded before the basaltic eruption1 so that the stream of molten lava took its course down the bed of this stream to the water's edge1 and grand sections have been laid bare by subsequent erosion along the banks4 ,pentagonal columns of black basalt form perpendicular walls1 first on one side1 then on the other2 while considerable masses of scori1 peperino1 and breccia appear at the head of the glen1 probably marking the orifice of eruption4 ,other eruptions of basalt occur1 one at ,mountar ez ,zara1 to the south of ,zerka ,man1 and another at ,wady ,ghuweir1 near the north-eastern end of the ,dead ,sea4 ,there are no lava-streams on the western side of the ,ghor1 or of the ,dead ,sea4#i ,the outburst of the celebrated thermal springs of ,callirrho1 together with nine or ten others1 along the channel of the ,zerka ,man1 is a circumstance which cannot be dissociated from the occurrence of basaltic lava at this spot4 ,in a reach of three miles1 according to ,tristram1 there are ten principal springs1 of which the fifth in descent is the largest2 but the seventh and eighth1 about half a mile lower down1 are the most remarkable1 giving forth large supplies of sulphurous water4 ,the tenth and last is the hottest of all1 indicating a temperature of #adc ,fahr4 ,thus it would appear that the heat increases with the depth from the upper surface of the table-land2 a result which might be expected1 supposing the heated volcanic rocks to be themselves the source of the high temperature4 ,to a similar cause may be attributed the hot-springs of ,hammath1 near ,tiberias1 and those of the ,yarmk near its confluence with the ,jordan4 ,some of these and other springs break out along1 or near1 the line of the great ,jordan-,arabah fault which ranges throughout the whole extent of this depression1 from the base of ,hermon to the ,gulf of ,akabah1 generally keeping close to the eastern margin of the valley4 7e47 ,the ,arabian ,desert4--,the basaltic lava-floods occupy a very large extent of the ,arabian ,desert1 from ,el ,hisma 7lat4 #bg #ce' ,n47 to the neighbourhood of ,mecca on the south1 a distance of about #ddj miles1 with occasional intervals4 ,the lava-sheets are called ,harras 7or ,harrat71 one of which1 ,harrat ,sfeina1 terminates about ten miles north of ,mecca4 ,the lava-sheets rest sometimes on the red sandstone1 at other times1 on the granite and other crystalline rocks of great geological antiquity4 ,in addition to the sheets of basalt1 numerous crater-cones rise from the basaltic platform at a level of #ejjj feet above the sea1 and two volcanic mountains1 rising far to the west of the principal range1 called respectively ,harrt ,jeheyma and ,h4 ,rodwa1 almost overlook the coast of the ,red ,sea4#aj 7f47 ,age of the ,volcanic ,eruptions4--,it is very clear that the first eruptions1 producing the great basaltic sheets of ,moab and ,arabia1 occurred after the principal features of the country had been developed4 ,the depression of the ,jordan-,arabah valley1 the elevation of the eastern side of this valley along the great fault line1 and the channels of the principal tributary streams1 such as those of the ,yarmk and ,zerka ,man1 all these had been eroded out before they were invaded by the molten streams of lava4 ,now1 as these physical features were developed and sculptured out during the ,miocene period1 as ,i have elsewhere shown to be the case1#aa we may with great probability refer the volcanic eruptions to the geological epoch following--namely1 the ,pliocene4 ,how far downwards towards the historic period the eruptions continued is not so certain4 ,dr4 ,daubeny1 quoting several passages from the ,old ,testament prophets1#ab says it might be inferred that volcanoes were in activity even so late as to admit of their being included within the limits of authentic history4 ,the poetic language and imagery used in these passages by the prophets certainly lends a probability to this view1 but nothing more4 ,on the other hand1 these regions have suffered through many centuries from the secondary effects of seismic action and subterranean forces1 and earthquake shocks have laid in ruins the great temples and palaces of ,palmyra1 ,baalbec1 and other cities of antiquity4 ,the same uncertainty regarding the time at which volcanic action died out1 with reference to the appearance of man on the scene1 hangs over the region of ,arabia and ,syria1 as we have seen to be the case in reference to the extinct volcanoes of ,auvergne1 the ,eifel1 and the ,lower ,rhine4 ,in all these cases the commencement and close of eruptive action appear to have been very much about the same period--namely1 the ,miocene period on the one hand1 and that at which man entered upon the scene on the other2 but in the case of ,syria and ,western ,palestine1 the close of the volcanic period may have been somewhat more than #bjjj ,b4,c4 #a ,lake ,phiala1 near the ,lake of ,huleh1 is also situated to the west of the ,jordan valley4 ,its origin1 according to ,tristram1 is volcanic4 #b ,schumacher1 ,the ,jauln1 ,quarterly ,statement of the ,palestine ,exploration ,fund1 #ahhf and #ahhh2 and ,across the ,jordan1 ,london1 #ahhf4 #c ,lartet1 ,voyage d',exploration de la mer ,morte 7,gologie71 ,paris1 #ahhj4 #d ,tristram1 ,land of ,moab1 ,london1 #ahgc2 and ,land of ,israel1 #ahff4 #e ,niebuhr1 ,beschreibung von ,arabien1 #aggc4 #f ,c4 ,m4 ,doughty1 ,arabia ,deserta1 #b vols41 #ahhh4 ,a generalised account of this volcanic region by the author will be found in the ,memoir on the ,physical ,geology of ,arabia ,petra1 and ,palestine1 ,palestine ,exploration ,fund1 #ahhg4 #g ,schumacher1 loc4 cit41 p4 #bdh4 #h ,land of ,israel1 p4 #dfa4 #i ,geology of ,arabia ,petra1 and ,palestine1 ,memoirs of the ,palestine ,exploration ,fund1 p4 #ie4 #aj ,doughty1 loc4 cit41 vol4 i41 plate vi41 p4 #daf4 ,an excellent geological sketch map accompanies this work4 #aa ,memoir of the ,geology of ,arabia ,petra1 and ,palestine1 chap4 vi4 p4 #fg4 #ab ,nahum1 i4 #e1 #f2 ,micah1 i4 #c1 #d2 ,isaiah1 lxiv4 #a-c2 ,jeremiah1 l4 #be4 ,,chapter ,,ii4 ,,the ,,volcanic ,,regions ,,of ,,north ,,america4 7a47 ,contrast between the ,eastern and ,western ,regions4--,in no point is there a more remarkable contrast between the physical structure of ,eastern and ,western ,america than in the absence of volcanic phenomena in the former and their prodigious development in the latter4 ,the great valley of the ,mississippi and its tributaries forms the dividing territory between the volcanic and non-volcanic areas2 so that on crossing the high ridges in which the western tributaries of ,america's greatest river have their sources1 and to which the name of the ,rocky ,mountains more properly belongs1 we find ourselves in a region which1 throughout the later ,tertiary times down almost to the present day1 has been the scene of volcanic operations on the grandest scale2 where lava-floods have been poured over the country through thousands of square miles1 and where volcanic cones1 vying in magnitude with those of ,etna1 ,vesuvius1 or ,hecla1 have established themselves4 ,this region1 generally known as ,the ,great ,basin1 is bounded on the west by the ,pacific ,range of mountains1 and includes portions of ,new ,mexico1 ,arizona1 ,california1 ,nevada1 ,utah1 ,colorado1 ,idaho1 ,oregon1 ,wyoming1 ,montana1 and ,washington4 ,to the south it passes into the mountainous region of ,mexico1 also highly volcanic2 and thence into the ridge of ,panama and the ,andes4 ,it cannot be questioned but that the volcanic nature of the ,great ,basin is due to the same causes which have originated the volcanic outbursts of the ,andes2 but1 from whatever cause1 the volcanic forces have here entered upon their secondary or moribund stage4 ,in the ,yellowstone ,valley1 geysers1 hot springs1 and fumaroles give evidence of this condition4 ,in other districts the lava-streams are so fresh and unweathered as to suggest that they had been erupted only a few hundred years ago2 but no active vent or crater is to be found over the whole of this wide region4 ,a few special districts only can here be selected by way of illustration of its special features in connection with its volcanic history4 7b47 ,the ,plateau ,country of ,utah and ,arizona4--,this tract1 which is drained by the ,colorado ,river and its tributaries1 is bounded on the north by the ,wahsatch range1 and extends eastwards to the base of the ,sierra ,nevada4 ,round its margin extensive volcanic tracts are to be found1 with numerous peaks and truncated cones--the ancient craters of eruption--of which ,mount ,san ,francisco is the culminating eminence4 ,south of the ,wahsatch1 and occupying the high plateaux of ,utah1 enormous masses of volcanic products have been spread over an area of #ijjj square miles1 attaining a thickness of between #cjjj and #djjj feet4 ,the earlier of these great lava-floods appear to have been trachytic1 but the later basaltic2 and in the opinion of ,captain ,dutton1 who has described them1 they range in point of time from the ,middle ,tertiary 7,miocene7 down to comparatively recent times4 7c47 ,the ,grand ,caon4--,to the south of the high plateaux of ,utah are many minor volcanic mountains1 now extinct2 and as we descend towards the ,grand ,caon of ,colorado we find numerous cinder-cones scattered about at intervals near the cliffs4#a ,extensive lava-fields1 surmounted by cinder-cones1 occupy the plateau on the western side of the ,grand ,caon2 and1 according to ,dutton1 the great sheets of basaltic lava1 of very recent age1 which occupy many hundred square miles of desert1 have had their sources in these cones of eruption4#b ,crossing to the east of the ,grand ,caon1 we find other lava-floods poured over the country at intervals1 surmounted by ,san ,francisco--a volcanic mountain of the first magnitude--which reaches an elevation1 according to ,wheeler1 of #ab1efb feet above the ocean4 ,it has long been extinct1 and its summit and flanks are covered with snow-fields and glaciers4 ,other parts of ,arizona are overspread by sheets of basaltic lava1 through which old necks of eruption1 formed of more solid lava than the sheets1 rise occasionally above the surface1 and are prominent features in the landscape4 ,further to the eastward in ,new ,mexico1 and near the margin of the volcanic region1 is another volcanic mountain little less lofty than ,san ,francisco1 called ,mount ,taylor1 which1 according to ,dutton1 rises to an elevation of #aa1cij feet above the ocean1 and #hbjj feet above the general level of the surrounding plateau of lava4 ,this mountain forms the culminating point of a wide volcanic tract1 over which are distributed numberless vents of eruption4 ,scores of such vents--generally cinder-cones--are visible in every part of the plateau1 and always in a more or less dilapidated condition4#c ,mount ,taylor is a volcano1 with a central pipe terminating in a large crater1 the wall of which was broken down on the east side in the later stage of its history4 ,illustration3 ,fig4 #be4--,mount ,shasta 7#ad1eaa feet71 a snow-clad volcanic cone in ,california1 with ,mount ,shastina1 a secondary crater1 on the right2 the valley between is filled with glacier-ice4--7,after ,dutton74 7d47 ,california4--,proceeding westwards into ,california1 we are again confronted with volcanic phenomena on a stupendous scale4 ,the coast range of mountains1 which branches off from the ,sierra ,nevada at ,mount ,pinos1 on the south1 is terminated near the northern extremity of the ,state by a very lofty mountain of volcanic origin1 called ,mount ,shasta1 which attains an elevation of #ad1eaa feet 7see ,fig4 #be74 ,this mountain was first ascended by ,clarence ,king in #ahgj1d and although forming1 as it were1 a portion of the ,pacific ,coast ,range1 it really rises from the plain in solitary grandeur1 its summit covered by snow1 and originating several fine glaciers4 ,the summit of ,mount ,shasta is a nearly perfect cone1 but from its north-west side there juts out a large crater-cone just below the snow-line1 between which and the main mass of the mountain there exists a deep depression filled with glacier ice4 ,this secondary crater-cone has been named ,mount ,shastina1 and round its inner side the stream of glacier ice winds itself1 sometimes surmounting the rim of the crater1 and shooting down masses of ice into the great caldron4 ,the length of this glacier is about three miles1 and its breadth about #djjj feet4 ,another very lofty volcanic mountain is ,mount ,rainier1 in the ,washington territory1 consisting of three peaks of which the eastern possesses a crater very perfect throughout its entire circumference4 ,this mountain appears to be formed mainly of trachytic matter4 ,proceeding further north into ,british territory1 several volcanic mountains near the ,pacific ,coast are said to exhibit evidence of activity4 ,of these may be mentioned ,mount ,edgecombe1 in lat4 #eg4c2 ,mount ,fairweather1 lat4 #eg4bj which rises to a height of #ad1icb feet2 and ,mount ,st4 ,elias1 lat4 #fj4e1 just within the divisional line between ,british and ,russian territory1 and reaching an altitude of #af1hfj feet4 ,this1 the loftiest of all the volcanoes of the ,north ,american continent1 except those of ,mexico1 may be considered as the connecting link in the volcanic chain between the continent and the ,aleutian ,islands4#e 7e47 ,lake ,bonneville4--,returning to ,utah we are brought into contact with phenomena of special interest1 owing to the inter-relations of volcanic and lacustrine conditions which once prevailed over large tracts of that territory4 ,the present ,great ,salt ,lake1 and the smaller neighbouring lakes1 those called ,utah and ,sevier1 are but remnants of an originally far greater expanse of inland water1 the boundaries of which have been traced out by ,mr4 ,c4 ,k4 ,gilbert1 and described under the name of ,lake ,bonneville4#f ,the waters of this lake appear to have reached their highest level at the period of maximum cold of the ,post-,pliocene period1 when the glaciers descended to its margin1 and large streams of glacier water were poured into it4 ,eruptions of basaltic lava from successive craters appear to have gone on before1 during1 and after the lacustrine epochs2 and the drying up of the waters over the greater extent of their original area1 now converted into the ,sevier ,desert1 and their concentration into their present comparatively narrow basins1 appears to have proceeded pari passu with the gradual extinction of the volcanic outbursts4 ,two successive epochs of eruption of basalt appear to have been clearly established--an earlier one of the ,provo ,age1 when the lava was extruded from the ,tabernacle craters1 and a later epoch1 when the eruptions took place from the ,ice ,spring craters4 ,the oldest volcanic rock appears to be rhyolite1 which peers up in two small hills almost smothered beneath the lake deposits4 ,its eruption was long anterior to the lake period4 ,on the other hand1 the cessation of the eruptions of the later basaltic sheets is evidently an event of such recent date that ,mr4 ,gilbert is led to look forward to their resumption at some future1 but not distant1 epoch4 ,as he truly observes1 we are not to infer that1 because the outward manifestations of volcanic action have ceased1 the internal causes of those manifestations have passed away4 ,these are still in operation1 and must make themselves felt when the internal forces have recovered their exhausted energies2 but perhaps not to the same extent as before4 7f47 ,region of the ,snake ,river4--,the tract of country bordering the ,snake ,river in ,idaho and ,washington is remarkable for the vast sheets of plateau-basalt with which it is overspread1 extending sometimes in one great flood farther than the eye can reach1 and what is still more remarkable1 they are often unaccompanied by any visible craters or vents of eruption4 ,in ,oregon the plateau-basalt is at least #b1jjj feet in thickness1 and where traversed by the ,columbia ,river it reaches a thickness of about #c1jjj feet4 ,the ,snake and ,columbia rivers are lined by walls of volcanic rock1 basaltic above1 trachytic below1 for a distance of1 in the former1 one hundred1 in the latter1 two hundred1 miles4 ,captain ,dutton1 in describing the ,high ,plateau of ,utah1 observes that the lavas appear to have welled up in mighty floods without any of that explosive violence generally characteristic of volcanic action4 ,this extravasated matter has spread over wide fields1 deluging the surrounding country like a tide in a bay1 and overflowing all inequalities4 ,here also we have evidence of older volcanic cones buried beneath seas of lava subsequently extruded4 7g47 ,fissures of ,eruption4--,the absence1 or rarity1 of volcanic craters or cones of eruption in the neighbourhood of these great sheets has led ,american geologists to the conclusion that the lavas were in many cases extruded from fissures in the earth's crust rather than from ordinary craters4#g ,this view is also urged by ,sir ,a4 ,geikie1 who visited the ,utah region of the ,snake ,river in #ahhj1 and has vividly described the impression produced by the sight of these vast fields of basaltic lava4 ,he says1 ,we found that the older trachytic lavas of the hills had been deeply trenched by the lateral valleys1 and that all these valleys had a floor of black basalt that had been poured out as the last of the molten materials from the now extinct volcanoes4 ,there were no visible cones or vents from which these floods of basalt could have proceeded4 ,we rode for hours by the margin of a vast plain of basalt stretching southward and westward as far as the eye could reach4444 ,i realised the truth of an assertion made first by ,richthofen1#h that our modern volcanoes1 such as ,vesuvius and ,etna1 present us with by no means the grandest type of volcanic action1 but rather belong to a time of failing activity4 ,there have been periods of tremendous volcanic energy1 when instead of escaping from a local vent1 like a ,vesuvian cone1 the lava has found its way to the surface by innumerable fissures opened for it in the solid crust of the globe over thousands of square miles4#i 7h47 ,volcanic ,history of ,western ,america4--,the general succession of volcanic events throughout the region of ,western ,america appears to have been somewhat as follows3--#aj ,the earliest volcanic eruptions occurred in the later ,eocene epoch and were continued into the succeeding ,miocene stage4 ,these consisted of rocks moderately rich in silica1 and are grouped under the heads of propylite and andesite4 ,to these succeeded during the ,pliocene epoch still more highly silicated rocks of trachytic type1 consisting of sanidine and oligoclase trachytes4 ,then came eruptions of rhyolite during the later ,pliocene and ,pleistocene epochs2 and lastly1 after a period of cessation1 during which the rocks just described were greatly eroded1 came the great eruptions of basaltic lava1 deluging the plains1 winding round the cones or plateaux of the older lavas1 descending into the river valleys and flooding the lake beds1 issuing forth from both vents and fissures1 and continuing intermittently down almost into the present day--certainly into the period of man's appearance on the scene4 ,thus the volcanic history of ,western ,america corresponds remarkably to that of the ,european regions with which we have previously dealt1 both as regards the succession of the various lavas and the epochs of their eruption4 7i47 ,the ,yellowstone ,park4--,the geysers and hot springs of the ,yellowstone ,park1 like those in ,iceland and ,new ,zealand1 are special manifestations of volcanic action1 generally in its secondary or moribund stage4 ,the geysers of the ,yellowstone occur on a grand scale2 the eruptions are frequent1 and the water is projected into the air to a height of over #bjj feet4 ,most of these are intermittent1 like the remarkable one known as ,old ,faithful1 the ,castle ,geyser1 and the ,giantess ,geyser described by ,dr4 ,hayden1 which ejects the water to a height of #bej feet4 ,the geyser-waters hold large quantities of silica and sulphur in solution1 owing to their high temperature under great pressure1 and these minerals are precipitated upon the cooling of the waters in the air1 and form circular basins1 often gorgeously tinted with red and yellow colours4#aa #a ,j4 ,w4 ,powell1 ,exploration of the ,caons of the ,colorado1 pp4 #aad1 #aif4 ,major ,powell describes a fault or fissure through which floods of lava have been forced up from beneath and have been poured over the surface4 ,many cinder-cones are planted along the line of this fissure4 #b ,capt4 ,c4 ,e4 ,dutton4 ,sixth ,ann4 ,rep4 ,u4,s4 ,geol4 ,survey1 #ahhd-he4 #c ,dutton1 loc4 cit41 chap4 iv4 p4 #afe4 #d ,amer4 ,jour4 ,science1 vol4 #c41 ser4 7#ahga74 ,a beautiful map of this mountain is given in the ,fifth ,annual ,report1 ,u4,s4 ,geol4 ,survey1 #ahhc-hd4 ,plate #dd4 #e ,daubeny1 loc4 cit41 p4 #dgd4 #f ,gilbert1 ,monograph ,u4,s4 ,geol4 ,survey1 vol4 i4 7#ahij74 #g ,powell1 ,exploration of the ,colorado ,river1 p4 #agg1 etc4 7#ahge74 ,hayden1 ,rep4 ,u4,s4 ,geol4 ,survey of the ,colorado1 etc4 7#ahga-hj74 #h ,richthofen1 ,natural ,system of ,volcanic ,rocks1 ,mem4 ,california ,acad4 ,sciences1 vol4 i4 7#ahfh74 #i ,geikie1 ,geological ,sketches at ,home and ,abroad1 p4 #bga 7#ahhb74 #aj ,prestwich1 ,geology1 vol4 i4 p4 #cgj1 quoting from ,richthofen4 #aa ,the origin of geysers is variously explained2 see ,prestwich1 ,geology1 vol4 i4 p4 #agj4 ,they are probably due to heated waters suddenly converted into steam by contact with rock at a high temperature4 ,,chapter ,,iii4 ,,volcanoes ,,of ,,new ,,zealand4 ,one other region of volcanic action remains to be noticed before passing on to the consideration of those of less recent age4 ,new ,zealand is an island wherein seem to be concentrated all the phenomena of volcanic action of past and present time4 ,though it is doubtful if the term active1 in its full sense1 can be applied to any of the existing craters 7with two or three exceptions1 such as ,tongariro and ,whakari ,island71 we find craters and cones in great numbers in perfectly fresh condition1 extensive sheets of trachytic and basaltic lavas1 ashes1 and agglomerates2 lava-floods descending from the ruptured craters of ashes and scori2 old crater-basins converted into lakes2 geysers1 hot springs and fumaroles which may be counted by hundreds1 and cataracts breaking over barriers of siliceous sinter2 and1 lastly1 lofty volcanic mountains vying in magnitude with ,vesuvius and ,etna4 ,all these wonderful exhibitions of moribund volcanic action seem to be concentrated in the northern island of ,auckland4 ,the southern island1 which is the larger1 also has its natural attractions1 but they are of a different kind2 chief of all is the grand range of mountains called1 not inappropriately1 the ,southern ,alps1 vying with its ,european representative in the loftiness of its peaks and the splendour of its snowfields and glaciers1 but formed of more ancient and solid rocks than those of the northern island4 7a47 ,auckland ,district4--,we are indebted to several naturalists for our knowledge of the volcanic regions of ,new ,zealand1 but chiefly to ,ferdinand von ,hochstetter1 whose beautiful maps and graphic descriptions leave nothing to be desired4#a ,in this work ,hochstetter was assisted by ,julius ,haast and ,sir ,j4 ,hector4 ,from their account we learn that the ,isthmus of ,auckland is one of the most remarkable volcanic districts in the world4 ,it is characterised by a large number of extinct cinder-cones1 in a greater or less perfect state of preservation1 and giving origin to lava-streams which have poured down the sides of the hills on to the plains4 ,besides these are others formed of stratified tuff1 with interior craters1 surrounding in mural cliffs eruptive cones of scori1 ashes1 and lapilli2 these cones are scattered over the isthmus and shores of ,waitemata and ,manukau4 ,the tuff cones and craters rise from a floor of ,tertiary sandstone and shale1 the horizontal strata of which are laid open in the precipitous bluffs of ,waitemata and ,manukau harbours2 they sometimes contain fossil shells of the genera ,pecten1 ,nucula1 ,cardium1 ,turbo1 and ,nerit4 ,as the volcanic tuff-beds are intermingled with the ,upper ,tertiary strata1 it is inferred that the first outbursts of volcanic forces occurred when the region was still beneath the waters of the ocean4 ,cross-sections show that the different layers slope both outwards 7parallel to the sides7 and inwards towards the bottom of the craters4 ,sometimes these craters have been converted into lakes1 as in the case of those of the ,eifel2 but generally they are dry or have a floor of morass4 ,of the crater-lakes1 those of ,kohuora1 five in number1 are perhaps the most remarkable2 and in the case of two of these the central cones of slag appear as islets rising from the surface of the waters4 ,the fresh-water lake ,pupuka has a depth of twenty-eight fathoms4 ,to the north of ,auckland ,harbour rises out of the waters of the ,hauraki ,gulf the cone of ,rangitoto1 #ibj feet high1 the flanks formed of rugged streams of basalt1 and the summit crowned by a circular crater of slag and ash1 out of the centre of which rises a second cone with the vent of eruption4 ,this is the largest and newest of the ,auckland volcanoes1 and appears to have been built up by successive outpourings of basaltic lava from the central orifice1 after the general elevation of the island4 ,illustration3 ,fig4 #bf4--;,forms of volcanic tuff cones1 with their cross-sections1 in the ,province of ,auckland4--,no4 #a4 ,simple tuff cone with central crater2 ,no4 #b4 ,outer tuff cone with interior cinder cone and crater2 ,no4 #c4 ,the same with lava-stream issuing from the interior cone4--7,after ,hochstetter47 ,before leaving the description of the tuff-cones1 which are a peculiar feature in the volcanic phenomena of ,new ,zealand1 and are of many forms and varieties1 we must refer to that of ,mount ,wellington 7,maunga ,rei74 ,this is a compound volcano1 in which the oldest and smallest of the group is a tuff-crater-cone1 exhibiting very beautifully the outward slope of its beds4 ,within this crater arise two cones of cinders1 each with small craters4 ,it would appear that after a long interval the larger of the two principal cones1 formed of cinders and known as ,mount ,wellington1 burst forth from the southern margin of the older tuff-cone1 and1 being built up to a height of #hej feet1 gradually overspread the sides of its older neighbour4 ,mount ,wellington itself has three craters1 and from these large streams of basaltic lava have issued forth in a westerly direction1 while a branch entered and partially filled the old tuff-crater to the northwards4 ,southwards from ,manukau ,harbour1 and extending a short distance from the coast-line to ,taranaki ,point1 there occurs a plateau of basalt-conglomerate 7,basaltkonglomerat71 with sheets of basaltic lava overspreading the ,tertiary strata4 ,these plateau-basalts are intersected by eruptive masses in the form of dykes1 but still there are no craters or cones of eruption to be seen2 so that we may infer that the sheets1 at least1 were extruded from fissures in the manner of those of the ,colorado or ,idaho regions of ,america4 ,proceeding still further south into the interior of the island1 we here find a lofty plateau of an average elevation of #b1jjj feet1 interposed between the ,tertiary beds of the ,upper and ,middle ,waikato1 and formed of trachytic and pitch-stone tuff1 amongst which arise old extinct volcanic cones1 such as those of ,karioi1 ,pirongia1 ,kakepuku1 ,maunga ,tautari1 ,aroha1 and many others4 ,these trachytic lavas would seem to be more ancient than the basaltic1 previously described4 7b47 ,taupo ,lake1 and surrounding district4--,but of all these volcanic districts1 none is more remarkable than that surrounding the ,taupo ,lake1 which lies amidst the ,tertiary strata of the ,upper ,waikato ,basin4 ,the surface of this lake is #a1bej feet above that of the ocean1 and its margin is enclosed within a border of rhyolite and pitchstone--rising into a mass of the same material #a1hjj feet high on the eastern side4 ,the form of the lake does not suggest that it is itself the crater of a volcano1 but rather that it was originated by subsidence4 ,on all sides1 however1 trachytic cones arise1 of which the most remarkable group lies to the south of the lake1 just in front of the two giant trachytic cones1 the loftiest in ,new ,zealand1 one called ,tongariro1 rising about #f1ejj feet1 and the other ,ruapahu1 which attains an elevation of over #i1jjj feet1 with the summit capped by snow4 ,these two lofty cones1 standing side by side1 are supposed by the ,maoris to be the husband and wife to whom were born the group of smaller cones above referred to as occupying the southern shore of ,taupo ,lake4 ,the volcano of ,tongariro may still be considered as in a state of activity1 as its two craters 7,ngauruhoe and ,ketetahi7 constantly emit steam1 and several solfataras break out on its flanks4#b 7c47 ,roto ,mahana4--,in a northerly direction from ,tongariro1 and distant from the coast by a few miles1 lies in the ,bay of ,plenty the second of the active volcanoes of ,new ,zealand1 the volcanic island of ,whakari 7,white ,island71 from the crater of which are constantly erupted vast masses of steam clouds4 ,the distance between these two active craters is #abj nautical miles2 and along the tract joining them steam-jets and geysers issue forth from the deep fissures through which the lava sheets have formerly been extruded4 ,numerous lakes also occupy the larger cavities in the ground2 and hot-springs1 steam-fumaroles and solfataras burst out in great numbers along the banks of the ,roto ,mahana ,lake and the ,kaiwaka ,river by which it is drained4 ,amongst such eruptions of hot-water and steam we might expect the formation of siliceous sinter1 and the deposition of sulphur and other minerals2 nor will our expectations be disappointed4 ,for here we have the wonderful terraces of siliceous sinter deposited by the waters entering ,roto ,mahana as they descend from the numerous hot-springs or pools near its margin4 ,all travellers concur in describing these terraces as the most wonderful of all the wonders of the ,lake district of ,new ,zealand--so great is their extent1 and so rich and varied is their colouring4 ,the beautiful map of ,roto ,mahana on an enlarged scale by ,hochstetter shows no fewer than ten large sinter terraces descending towards the margin of this lake1 besides several mud-springs1 fumaroles1 and solfataras4 ,but the largest and most celebrated of all the sinter terraces has within the last few years been buried from view beneath a flood of volcanic trass1 or mud1 an event which was as unexpected as it was unwelcome4 ,in ,may1 #ahhg1 the mountain of ,tarawera1 which rises to the north-east of ,roto ,mahana1 and on the line of eruption above described1 suddenly burst forth into violent activity1 covering the country for miles around with clouds of ashes1 and1 pouring down torrents of mud1 completely enveloped the beautiful terrace of sinter which had previously been one of the wonders of ,new ,zealand4 ,by the same eruption several human beings were entombed1 and their residences destroyed4 ,the waters of ,roto ,mahana1 together with the hot-springs and fountains are fed from rain1 and from the waters of ,taupo ,lake1 which1 sinking through fissures in the ground1 come in contact with the interior heated matter1 and thus steam at high temperature and pressure is generated4#c 7d47 ,moribund condition of ,new ,zealand ,volcanoes4--,from what has been said1 it will be inferred that in the case of ,new ,zealand1 as in those of ,auvergne1 the ,eifel and ,lower ,rhine1 ,arabia1 and ,western ,america1 we have an example of a region wherein the volcanic forces are well-nigh spent1 but in which they were in a state of extraordinary activity throughout the later ,tertiary1 down to the commencement of the present epoch4 ,in most of these cases the secondary phenomena of vulcanicity are abundantly manifest2 but the great exhibitions of igneous action1 when the plains were devastated by sheets of lava1 and cones and craters were piled up through hundreds and thousands of feet1 have for the present1 at least1 passed away4 #a ,geol4-topographischer ,atlas von ,neu-,seeland1 von ,dr4 ,ferd4 von ,hochstetter und ,dr4 ,a4 ,petermann4 ,gotha3 ,justus ,perthes 7#ahfc74 ,also ,new ,zealand1 trans4 by ,e4 ,sauter1 ,stuttgart 7#ahfg74 #b ,tongariro was visited in #ahea by ,mr4 ,h4 ,dyson1 who describes the eruption of steam4 #c ,mr4 ,froude figures and describes the two terraces1 the ,white and ,pink1 in ,oceana1 #bnd edition1 pp4 #bhe-bia4 ,,part ,,iv4 ,,tertiary ,,volcanic ,,districts ,,of ,,the ,,british ,,isles4 ,,chapter ,i4 ,,antrim4 ,it is an easy transition to pass from the consideration of ,european and other dormant1 or extinct1 volcanic regions to those of the ,british ,isles1 though the volcanic forces may have become in this latter instance quiescent for a somewhat longer period4 ,in all the cases we have been considering1 whether those of ,central ,italy1 of the ,rhine and ,moselle1 of ,auvergne1 or of ,syria and ,arabia1 the cones and craters of eruption are generally present entire1 or but slightly modified in form and size by the effects of time4 ,but in the case of the ,tertiary volcanic districts of the ,british ,isles this is not so4 ,on the contrary1 these more prominent features of vulcanicity over the surface of the ground have been removed by the agents of denudation1 and our observations are confined to the phenomena presented by extensive sheets of lava and beds of ash1 or the stumps and necks of former vents of eruption1 together with dykes of trap by which the plateau-lavas are everywhere traversed or intersected4 ,the volcanic region of the ,british ,isles extends at intervals from the ,north-east of ,ireland through the ,island of ,mull and adjoining districts on the mainland of ,morvern and ,ardnamurchan into the ,isle of ,skye1 and comprises several smaller islets2 the whole being included in the general name of the ,inner ,hebrides4 ,it is doubtful if the volcanic lavas of ,co4 ,antrim were ever physically connected with those of the west of ,scotland1 though they may be considered as contemporary with them2 and in all cases the existing tracts of volcanic rock are mere fragments of those originally formed by the extrusion of lavas from vents of eruption4 ,in addition to these1 there are large areas of volcanic rock overspread by the waters of the ocean4 7a47 ,geological ,age4--,the ,british volcanic eruptions now under consideration are all later than the ,cretaceous period4 ,throughout ,antrim1 and in parts of ,mull1 the lavas are found resting on highly eroded faces either of the ,upper ,chalk 7,fig4 #bg71 or1 where it has been altogether denuded away1 on still older ,mesozoic strata4 ,from the relations of the basaltic sheets of ,antrim to the ,upper ,chalk1 it is clear that the latter formation1 after its deposition beneath the waters of the ,cretaceous seas1 was elevated into dry land and exposed to a long period of subarial erosion before the first sheets of lava invaded the surface of the ground4 ,we are1 therefore1 tolerably safe in considering the first eruptions to belong to the ,tertiary period2 but the evidence1 derived as it is exclusively from plant remains1 is somewhat conflicting as to the precise epoch to which the lavas and beds of tuff containing the plant-remains are to be referred4 ,the probabilities appear to be that they are of ,miocene age2 and if so1 the trachytic lavas1 which in ,antrim are older than those containing plants1 may be referred to a still earlier epoch--namely1 that of the ,eocene4#a ,as plant remains are not very distinctive1 the question regarding the exact time of the first volcanic eruptions will probably remain for ever undecided2 but we are not likely to be much in error if we consider the entire volcanic period to range from the close of the ,eocene to that of the ,miocene2 by far the greater mass of the volcanic rocks being referable to the latter epoch4 ,in describing the ,british volcanic districts it will be most convenient to deal with them in three divisions--viz41 those of ,antrim1 ,mull1 and ,skye1 commencing with ,antrim4#b 7b47 ,volcanic ,area4--,the great sheets of basalt and other volcanic products of the ,north-east of ,ireland overspread almost the whole of the ,county ,antrim1 and adjoining districts of ,londonderry and ,tyrone1 breaking off in a fine mural escarpment along the northern shore of ,belfast ,lough and the sea coast throughout the whole of its range from ,larne ,harbour to ,lough ,foyle2 the only direction in which these features subside into the general level of the country being around the shores of ,lough ,neagh4 ,several outliers of the volcanic sheets are to be found at intervals around the great central plateau2 such as those of ,rathlin ,island1 ,island ,magee1 and ,scrabo ,hill in ,co4 ,down4 ,the area of the basaltic plateau may be roughly estimated at #b1jjj square miles4 ,illustration3 ,fig4 #bg4--,the ,white ,rocks1 ,portrush1 ,co4 ,antrim1 showing the plateau-basalt resting on an eroded surface of the ,upper ,chalk1 with bands of flint4--7,from a photograph47 ,the truncated edges of this marginal escarpment rising to levels of #a1jjj to #a1bfj feet1 as in the case of ,benevenagh in ,co4 ,derry1 and #a1hbe feet at ,mullaghmore1 attest an originally greatly more extended range of the basaltic sheets2 and it is not improbable that at the close of the ,miocene epoch they extended right across the present estuary of ,lough ,foyle to the flanks of the mountains of ,inishowen in ,donegal in one direction1 and to those of ,slieve ,croob in the other4 ,in the direction of ,scotland the promontories of ,kintyre and ,islay doubtless formed a part of the original margin4 ,throughout this vast area the volcanic lavas rest on an exceedingly varied rocky floor1 both as regards composition and geological age4 7,see ,fig4 #bh47 ,throughout the central1 southern1 eastern1 and northern parts of their extent1 the ,chalk formation may be considered to form this floor2 but in the direction of ,armagh and ,tyrone1 towards the southwestern margin1 the basaltic sheets are found resting indiscriminately on ,silurian1 ,carboniferous1 and ,triassic strata4 ,the general relations of the plateau-basalts to the underlying formations show1 that at the close of the ,cretaceous period there had been considerable terrestrial disturbances and great subarial denudation1 resulting in some cases in the complete destruction of the whole of the ,cretaceous strata1 before the lava floods were poured out2 owing to which1 these latter are found resting on formations of older date than the ,cretaceous4#c ,illustration3 ,fig4 #bh4--,section across the volcanic plateau of ,antrim1 from the ,highlands of ,inishowen1 ,co4 ,donegal1 on the ,n4,w41 to ,belfast ,lough on the ,s4,e41 to show the relations of the volcanic rocks to the older formations4--,b4 ,basaltic sheets breaking off in high escarpments2 ,t4 ,trachyte porphyry of ,tardree mountain rising from below the newer plateau-basalts2 ,c4 ,upper ,chalk with flints2 ,n4,r4 ,new ,red marl and sandstone 7,trias72 ,m4 ,metamorphic beds of quartzite1 various schists and crystalline limestone2 ,f4 ,large fault4 #a ,mr4 ,j4 ,starkie ,gardner1 from a recent comparison of the plant-remains of ,antrim and ,mull1 concludes that that they might belong to any age between the beginning and the end of the warmer ,eocene period2 and that they cannot be of earlier1 and are unlikely to be of later1 date4--,trans4 ,palont4 ,soc41 vol4 xxxvii4 7#ahhc74 #b ,having dealt with this district rather fully in ,the ,physical ,geology and ,geography of ,ireland 7,edit4 #ahia1 p4 #ha71 and also in my ,presidential ,address 7,section ,c47 at the meeting of the ,british ,association1 #ahgd1 a brief review of the subject will be sufficient here1 the reader being referred to the former treatises for fuller details4 ,the following should also be consulted3 ,gen4 ,portlock1 ,geology of ,londonderry and ,tyrone 7#ahdc72 ,sir ,a4 ,geikie1 ,history of ,volcanic ,action during the ,tertiary ,period in the ,british ,isles1 ,trans4 ,roy4 ,soc4 ,edinburgh1 #ahhh2 and the ,descriptive ,memoirs of the ,geological ,survey relating to this tract of country4 #c ,owing to the superposition of the basaltic masses on beds of chalk throughout a long line of coast1 we are presented with the curious spectacle of the whitest rocks in nature overlain by the blackest1 as may be seen in the cliffs at ,larne1 ,glenarm1 ,kinbane and ,portrush4 7,see ,fig4 #bg47 ,,chapter ,,ii4 ,,succession ,,of ,,volcanic ,,eruptions4 7c47 ,first ,stage4--,the earliest eruptions of lava in the ,north-east of ,ireland belonged to the highly acid varieties1 consisting of quartz-trachyte with tridymite4#a ,this rock rises to the surface at ,tardree and ,brown ,dod hills and ,templepatrick4 ,it consists of a light-greyish felsitic paste enclosing grains of smoke-quartz1 crystals of sanidine1 plagioclase and biotite1 with a little magnetite and apatite4 ,it is a rock of peculiar interest from the fact that it is almost unique in the ,british ,islands1 and has its petrological counterpart rather amongst the volcanic hills of the ,siebengebirge than elsewhere4 ,it is generally consolidated with the columnar structure4 ,illustration3 ,fig4 #bi4--,part of the section shown in the quarry at ,templepatrick1 showing the superposition of the basalt 7d7 to the trachyte 7b71 with the intervening bed of flint gravel 7c74 ,all these rocks are seen to rest upon an eroded surface of the ,chalk formation 7a74 ,the trachyte appears to have been extruded from one or more vents in a viscous condition1 the principal vent being probably situated under ,tardree mountain1 where the rock occurs in greatest mass1 and it probably arose as a dome-shaped mass1 with a somewhat extended margin1 above the floor of ,chalk which formed the surface of the ground4#b 7,fig4 #bg47 ,at ,templepatrick the columnar trachyte may be observed resting on the ,chalk1 or upon a layer of flint gravel interposed between the two rocks1 and which has been thrust out of position by a later intrusion of basalt coming in from the side4#c ,it is to be observed1 however1 that the trachytic lavas nowhere appear cropping out along with the sheets of basalt around the escarpments overlooking the sea1 or inland2 showing that they did not spread very far from their vents of eruption2 a fact illustrating the lower viscosity1 or fluidity1 of the acid lavas as compared with those of the basic type4 7d47 ,second ,stage4--,after an interval1 probably of long duration1 a second eruption of volcanic matter took place over the entire area2 but now the acid lavas of the first stage are replaced by basic lavas4 ,now1 for the first time1 vast masses of basalt and dolerite are extruded both from vents of eruption and fissures2 and1 owing to their extreme viscosity1 spread themselves far and wide until they reach the margin of some uprising ground of old ,palozoic or ,metamorphic rocks by which the volcanic plain is almost surrounded4 ,the great lava sheets thus produced are generally more or less amorphous1 vesicular and amygdaloidal1 often exhibiting the globular concentric structure1 and weathering rapidly to a kind of ferruginous sand or clay under the influence of the atmosphere4 ,successive extrusions of these lavas produce successive beds1 which are piled one over the other in some places to a depth of #fjj feet2 and at the close of the stage1 when the volcanic forces had for the time exhausted themselves1 the whole of the ,north-east of ,ireland must have presented an aspect not unlike that of one of those great tracts of similar lava in the region of ,idaho and the ,snake ,river in ,western ,america1 described in a previous chapter4 7e47 ,third ,stage 7,inter-volcanic74--,the third stage may be described as inter-volcanic4 ,owing to the formation of a basin1 probably not deep1 and with gently sloping sides1 a large lake was formed over the centre of the area above described4 ,its floor was basalt1 and the streams from the surrounding uplands carried down leaves and stems of trees1 strewing them over its bed4 ,occasionally eruptions of ash took place from small vents1 forming the ash-beds with plants found at ,ballypallidy1 ,glenarm1 and along the coast as at ,carrick-a-raide4 ,the streams also brought down sand and gravel from the uprising domes of trachyte1 and deposited them over the lake-bed along with the erupted ashes4#d ,the epoch we are now referring to was one of economic importance2 as1 towards its close1 there was an extensive deposition of pisolitic iron-ore over the floor of the lake1 sometimes to the depth of two or three feet4 ,this ore has been extensively worked in recent years4 ,illustration3 ,fig4 #cj4--;,cliff section above the ,giant's ,causeway1 coast of ,co4 ,antrim1 showing successive tiers of basaltic lava1 with intervening bands of bole4 7f47 ,fourth ,stage 7,volcanic74--,the last stage described was brought to a termination by a second outburst of basic lavas on a scale probably even grander than the preceding4 ,these lavas consisting of basalt and dolerite1 with their varieties1 and extruded from vents and fissures1 spread themselves in all directions over the pre-existing lake deposits or the older sheets of augitic lava1 and probably entirely buried the trachytic hills4 ,these later sheets solidified into more solid masses than those of the second stage4 ,they form successive terraces with columnar structure1 each terrace differing from that above and below it in the size and length of the columns1 and separated by thin bands of bole 7decomposed lava71 often reddish in colour1 clearly defining the limits of the successive lava-flows4 ,nowhere throughout the entire volcanic area are these successive terraces so finely laid open to view as along the north coast of ,antrim1 where the lofty mural cliffs1 worn back into successive bays with intervening headlands by the irresistible force of the ,atlantic waves1 present to the spectator a vertical section from #cjj to #djj feet in height1 in which the successive tiers of columnar basalt1 separated by thin bands of bole1 are seen to rise one above the other from the water's edge to the summit of the cliff1 as shown in ,fig4 #cj4 ,here1 also1 at the western extremity of the line of cliffs we find that remarkable group of vertical basaltic columns1 stretching from the base of the cliff into the ,atlantic1 and known far and wide by the name of ,the ,giant's ,causeway1 the upper ends of the columns forming a tolerably level surface1 gently sloping seawards1 and having very much the aspect of an artificial tesselated pavement on a huge scale4 ,a portion of the ,causeway1 with the cliff in the background1 is shown in the figure 7,fig4 #ca74 ,the columns are remarkable for their symmetry1 being generally hexagonal1 though occasionally they are pentagons1 and each column is horizontally traversed by joints of the ball-and-socket form1 thus dividing them into distinct courses of natural masonry4 ,these are very well shown in the accompanying view of the remarkable basaltic pillars known as ,the ,chimneys1 which stand up from the margin of the headland adjoining the ,causeway1 monuments of past denudation1 as they originally formed individuals amongst the group belonging to one of the terraces in the adjoining coast4#e 7,fig4 #cb74 ,illustration3 ,fig4 #ca4--,the ,giant's ,causeway1 formed of basaltic columns in a vertical position1 and of pentagonal or hexagonal section2 above the ,causeway is seen a portion of the cliff composed of tiers of lava with intervening bands of bole1 etc4--7,from a photograph47 ,illustration3 ,fig4 #cb4--,the ,chimneys1 columns of basalt on slope of cliff overlooking the ,atlantic1 north coast of ,co4 ,antrim4 ,the horizontal segments1 or cup-and-ball joints1 of the columns are well shown in this figure4 7,from a photograph47 7g47 ,original ,thickness of the ,antrim ,lavas4--,it is impossible to determine with certainty what may have been the original thickness of the accumulated sheets of basic lavas with their associated beds of ash and bole4 ,the greatest known thickness of the lower zone of lavas is1 as ,i have already stated1 about #fjj feet4 ,the intermediate beds of ash and bole sometimes attain a thickness of #dj feet1 and the upper group of basalt about #djj feet2 these together would constitute a series of over #a1jjj feet in thickness4 ,but this amount1 great as it is1 is undoubtedly below the original maximum1 as the uppermost sheets have been removed by denuding agencies1 we know not to what extent4 ,nor is it of any great importance4 ,sufficient remains to enable us to form a just conception of the magnitude both as regards thickness and extent of the erupted matter of the ,miocene period over the ,north-east of ,ireland and adjoining submerged tracts1 and of the magnitude of the volcanic operations necessary for the production of such masses4 7h47 ,volcanic ,necks4--,as already remarked1 no craters of eruption survive throughout the volcanic region of the ,north-east of ,ireland1 owing to the enormous extent of the denudation which this region has undergone since the ,miocene ,epoch2 but the old necks of such craters--in other words1 the pipes filled with either solid basalt1 or basalt and ashes--are still to be found at intervals over the whole area4 ,owing to the greater solidity of the lava which filled up these necks over the plateau-basaltic sheets which surround them1 they appear as bosses or hills rising above the general level of the ground4 ,one of these bosses of highly columnar basalt occurs between ,portrush and ,bushmills1 not far from ,dunluce ,castle1 another at ,scawt ,hill1 near ,glenarm1 and a third at ,carmoney ,hill above ,belfast ,lough4 ,but by far the most prominent of these old solidified vents of eruption is that of ,sleamish1 a conspicuous mountain which rises above the general level of the plateau near ,ballymena1 and attains an elevation of #a1dcg feet above the sea4 ,seen from the west1 the mountain has the appearance of a round-topped cone2 but on examination it is found to be in reality a huge dyke1 breaking off abruptly towards the north-west1 in which direction it reaches its greatest height1 then sloping downwards towards the east4 ,this form suggests that ,sleamish is in reality one of the fissure-vents of eruption rather than the neck of an old volcano4 ,the rock of which it is formed consists of exceedingly massive1 coarsely-crystalline dolerite1 rich in olivine1 and divided into large quadrangular blocks by parallel joint planes4 ,its junction with the plateau-basalt from which it rises can nowhere be seen2 but at the nearest point where the two rocks are traceable the plateau-basalt appears to be somewhat indurated2 breaking with a splintery fracture and a sharp ring under the hammer1 suggesting that the lava of ,sleamish had been extruded through the horizontal sheets1 and had considerably indurated the portions in contact with1 or in proximity to1 it4#f ,amongst the vents filled with ash and agglomerate1 the most remarkable is that of ,carrick-a-raide1 near ,ballycastle4 ,it forms this rocky island and a portion of the adjoining coast1 where the beds of ash are finely displayed2 consisting of fragments and bombs of basalt1 with pieces of chalk1 flint1 and peperino1 which is irregularly bedded4 ,these ash-beds attain a thickness of about #abj feet just below the road to ,ballycastle1 but rapidly tail out in both directions from the locality of the vent4 ,just below the ash-beds1 the white chalk with flints may be seen extending down into the sea-bed4 ,nowhere in ,antrim is there such a display of volcanic ash and agglomerate as at this spot4#g 7i47 ,dykes3 ,conditions under which they were ,erupted4--,no one can visit the geological sections in ,co4 ,antrim and the adjoining districts of ,down1 ,armagh1 ,derry1 and ,tyrone1 without being struck by the great number and variety of the igneous dykes by which the rocks are traversed4 ,the great majority of these dykes are basaltic1 and they are found traversing all the formations1 including the ,cretaceous and ,tertiary basaltic sheets4 ,the ,carlingford and ,mourne ,mountains are seamed with such dykes1 and they are splendidly laid open to view along the coast south of ,newcastle in ,co4 ,down1 as also along the ,antrim coast from ,belfast to ,larne4 ,the fine old castle of ,carrickfergus has its foundations on one of those dyke-like intrusions1 but one of greater size than ordinary4 ,all the dykes here referred to are not1 however1 of the same age1 as is conclusively proved by sections amongst the ,mourne ,mountains where cliffs of ,lower ,silurian strata1 superimposed on the intrusive granite of the district1 exhibit two sets of basaltic dykes--one 7the older7 abruptly terminated at the granite margin1 the other and newer penetrating the granite and ,silurian rocks alike4 ,it is not improbable that the older dykes belong to the ,carboniferous or ,permian age1 while the newer are with equal probability of ,tertiary age4 ,sir ,a4 ,geikie has shown that the ,tertiary dykes of the ,north of ,ireland are representatives of others occurring at intervals over the ,north of ,england1 and ,central and ,western ,scotland1 all pointing towards the central region of volcanic activity2 or in a parallel direction thereto1 approximating to the ,n4,w4 in ,ireland1 the ,island of ,islay1 and ,east ,argyleshire1 but in the centre of ,scotland generally ranging from east to west4#h ,the area affected by the dykes of undoubted ,tertiary age ,geikie estimates at no less than #dj1jjj square miles--a territory greater than either ,scotland or ,ireland1 and equal to more than a third of the total land-surface of the ,british ,isles2#i and he regards them as posterior to the rest of the geological structures of the regions which they traverse4 ,it is clear that the dykes referred to belong to one great system of eruption or intrusion2 and they may be regarded as the manifestation of the final effort of internal forces over this region of the ,british ,isles4 ,they testify to the existence of a continuous magma 7or shell7 of augitic lava beneath the crust2 and as the aggregate horizontal extent of all these dykes1 or of the fissures which they fill1 must be very considerable1 it is clear that the crust through which they have been extruded has received an accession of horizontal space1 and has been fissured by forces acting from beneath1 as the late ,mr4 ,hopkins1 of ,cambridge1 had explained on mechanical grounds in his elaborate essay many years ago4#aj ,this view occurred to myself when examining the region of the ,north-east of ,ireland1 but ,i was not then aware that it had been dealt with on mathematical principles by so eminent a mathematician4 ,the bulging of the crust is a necessary consequence of the absence of plication of the strata due to the extrusion of this enormous quantity of molten lava2 and the intrusion of thousands of dykes over the ,north-east of ,ireland1 unaccompanied by foldings of the strata1 must have added a horizontal space of several thousand feet to that region4#aa #a ,a peculiar form of crystalline quartz first recognized in this rock by a distinguished ,german petrologist1 the late ,prof4 ,a4 von ,lasaulx1 who visited the district in #ahgf4 #b ,sir ,a4 ,geikie has disputed the correctness of the view1 which ,i advocated as far back as #ahgd1 that the trachytic lavas of ,antrim are the earliest products of volcanic action2 but at the time he wrote his paper on the volcanic history of these islands1 it was not known that pebbles of this trachyte are largely distributed amongst the ash-beds which occur in the very midst of the overlying basaltic sheets1 as ,i shall have to explain later on4 ,this discovery puts the question at rest as regards the relations of the two sets of rocks4 #c ,this remarkable section at the chalk quarries of ,templepatrick the author has figured and described in the ,physical ,geology and ,geography of ,ireland1 p4 #ii1 #bnd edit4 7#ahia71 where the reader will find the subject discussed more fully than can be done here4 #d ,these pebbles were first noticed by ,mr4 ,mc,henry1 of the ,irish ,geological ,survey1 in #ahij4 #e ,the vertical position of the columns of the ,giant's ,causeway is rather enigmatical4 ,the ,causeway cannot be a dyke1 as has often been supposed1 otherwise the columns would have been horizontal1 i4e41 at right angles to the sides of the dyke4 ,mr4 ,r4 ,g4 ,symes1 of the ,geological ,survey1 has suggested that the ,causeway columns have been vertically lowered between two lines of fault1 and that originally they formed a portion of the tier of beautiful columns seen in the cliff above1 and known as ,the ,organ4 #f ,sleamish and several other of the ,antrim vents are described by ,sir ,a4 ,geikie in the monograph already referred to1 loc4 cit41 p4 #aja1 et seq4 ,also in the ,expl4 ,memoirs of the ,geological ,survey of ,ireland4 #g ,a diagrammatised section of the ,carrick-a-raide volcanic neck is given by ,sir ,a4 ,geikie1 loc4 cit41 p4 #aje4 #h ,geikie1 loc4 cit41 p4 #bi1 et seq4 #i ,p4 #cb4 ,the view that the crust of the earth has been horizontally extended by the intrusion of dykes is noticed by ,mc,culloch in reference to the dykes of ,skye4 #aj ,hopkins1 ,cambridge ,phil4 ,trans41 vol4 vi4 p4 #a 7#ahcf74 #aa ,as suggested in my ,presidential ,address to ,section ,c4 of the ,british ,association at ,belfast1 #ahgd4 ,,chapter ,,iii4 ,,island ,,of ,,mull ,,and ,,adjoining ,,coast4 ,the ,island of ,mull1 with the adjoining districts of ,morvern and ,ardnamurchan1 forms the more southern of the two chief centres of ,tertiary volcanic eruptions in the ,west of ,scotland1 that of ,skye being the more northern4 ,these districts have been the subject of critical and detailed study by several geologists1 from ,mc,culloch down to the present day2 and amongst the more recent1 ,sir ,archibald ,geikie and ,professor ,judd hold the chief place4 ,unfortunately1 the interpretation of the volcanic phenomena by these two accomplished observers has led them to very different conclusions as regards several important points in the volcanic history of these groups of islands2 as1 for example1 regarding the relative ages of the plateau-basalts and the acid rocks1 such as the trachytes and granophyres2 again as regards the presence of distinct centres of eruption2 and also as regards the relations of the gabbros of ,skye to the basaltic sheets4 ,such being the case1 it would appear the height of rashness on the part of the writer1 especially in the absence of a detailed examination of the sections over the whole region1 to venture on a statement of opinion regarding the points at issue2 and he must1 therefore1 content himself with a brief account of the phenomena as gathered from a perusal of the writings of these and other observers1#a guided also to some extent by the analogous phenomena presented by the volcanic region of the ,north-east of ,ireland4 7a47 ,general ,features4--,as in the case of the ,antrim district1 the ,island of ,mull and adjoining tracts present us with the spectacle of a vast accumulation of basaltic lava-flows1 piled layer upon layer1 with intervening beds of bole and tuff1 up to a thickness1 according to ,geikie1 of about #c1ejj feet4 ,at the grand headland of ,gribon1 on the west coast1 the basaltic sheets are seen to rise in one sheer sweep to a height of #a1fjj feet1 and then to stretch away with a slight easterly dip under ,ben ,more at a distance of some eight miles4 ,this mountain1 the upper part of which is formed of beds of ashes1 reaches an elevation of #c1afi feet1 so that the accumulated thickness of the beds of basalt under the higher part of the mountain must be at least equal to the amount stated above--that is1 twice as great as the representative masses of ,antrim4 ,the base of the volcanic series is seen at ,carsaig and ,gribon to rest on ,cretaceous and ,jurassic rocks1 like those of ,antrim2 hence the ,tertiary age is fully established by the evidence of superposition4 ,this was further confirmed by the discovery by the ,duke of ,argyll1#b some years ago 7#ahej71 of bands of flint-gravel and tuff1 with dicotyledonous leaves amongst the basalts of ,ardtun ,head4 ,the basement beds of tuff and gravel contain1 besides pebbles of flint and chalk1 others of sanidine trachyte1 showing that highly acid lavas had been extruded and consolidated before the first eruption of the plateau-basalts2 another point of analogy between the volcanic phenomenon of ,antrim and the ,inner ,hebrides4 ,these great sheets of augitic lava extend over the whole of the northern tract of ,mull1 the ,isles of ,ulva and ,staffa1 and for a distance of several miles inwards from the northern shore of the ,sound of ,mull1 covering the wild moorlands of ,morvern and ,ardnamurchan1 where they terminate in escarpments and outlying masses1 indicating an originally much more extended range than at the present day4 ,the summits of ,ben ,more and its neighbouring height1 ,ben ,buy1 are formed of beds of ash and tuff4 ,the volcanic plateau is1 according to ,judd1 abruptly terminated along the southern side by a large vault1 bringing the basalt in contact with ,palozoic rocks4#c 7b47 ,granophyres4--,the greater part of the tract lying to the south of ,loch na ,keal1 which almost divides ,mull into two islands1 and extending southwards and eastwards to the shores of the ,firth of ,lorn and the ,sound of ,mull1 is formed of a peculiar group of acid 7or highly silicated7 rocks1 classed under the general term of ,granophyres4 ,these rocks approach towards true granites in one direction1 and through quartz-porphyry and felsite to rhyolite in another--probably depending upon the conditions of cooling and consolidation4 ,in their mode of weathering and general appearance on a large scale1 they present a marked contrast to the basic lavas with which they are in contact from the coast of ,l4 na ,keal to that of ,l4 ,buy4 ,the nature of this contact1 whether indicating the priority of the granophyres to the plateau-basalts or otherwise1 is a matter of dispute between the two observers above named2 but the circumstantial account given by ,sir ,a4 ,geikie1#d accompanied by drawings of special sections showing this contact1 appears to prove that the granophyre is the newer of the two masses of volcanic rock1 and that it has been intruded amongst the basaltic-lavas at a late period in the volcanic history of these islands4 ,a copy of one of these sketches is here given 7,fig4 #cc71 according to which the felsite is shown to penetrate the basaltic sheets at ,alt na ,searmoin in ,mull2 other sections seen at ,cruach ,torr an ,lochain1 and on the south side of ,beinn ,fada1 appear to lead to similar conclusions4 ,these rocks are penetrated by numerous basaltic dykes4 ,illustration3 ,fig4 #cc4--,section at ,alt na ,searmoin1 ,mull1 to show the intrusion of felsite 7or granophyre7 7b7 into basalt and dolerite 7a7 of the plateau-basalt series4--7,geikie47 7c47 ,representative ,rocks of ,mourne and ,carlingford1 ,ireland4--,assuming ,sir ,a4 ,geikie's view to be correct1 it is possible that we may have in the granite and quartz-porphyries of ,mourne and ,carlingford representatives of the granites1 granophyres1 and other acid rocks of the later period of ,mull4 ,the granite of ,mourne is peculiar in structure1 and differs from the ordinary type of that rock in which the silica forms the ground mass4 ,in the case of the granite of the ,mourne ,mountains1 the rock consists of a crystalline granular aggregate of orthoclase1 albite1 smoke-quartz1 and mica2 it is also full of drusy cavities1 in which the various minerals crystallise out in very perfect form4 ,as far as regards direct evidence1 the age of this rock can only be stated to be post-,carboniferous1 and earlier than certain ,tertiary basaltic dykes by which it is traversed4 ,the granophyres of ,mull are traversed by similar dykes1 which are representatives of the very latest stage of volcanic action in the ,british ,islands4 ,the author is therefore inclined to concur with ,sir ,a4 ,geikie in assigning to the granite of the ,mourne ,mountains1 and the representative felsitic rocks of the ,carlingford ,mountains1 a ,tertiary age--in which case the analogy between the volcanic phenomena of the ,inner ,hebrides and of the ,north-east of ,ireland would seem to be complete4#e #a ,geikie1 ,proc4 ,roy4 ,soc4 ,edinburgh 7#ahfg72 ,brit4 ,assoc4 ,rep4 7,dundee1 #ahfg72 ,tertiary ,volcanic ,rocks of the ,british ,isles1 ,quart4 ,journ4 ,geol4 ,soc41 vol4 xxvii4 p4 #bgi2 also1 ,history of ,volcanic ,action in ,british ,isles1 ,trans4 ,roy4 ,soc4 ,edin4 7#ahhh72 ,judd1 ,on the ,ancient ,volcanoes of the ,highlands1 etc41 ,quart4 ,journ4 ,geol4 ,soc41 vol4 xxx4 p4 #bcc2 and ,volcanoes1 p4 #aci4 #b ,brit4 ,assoc4 ,rep4 for #ahej1 p4 #gj4 #c ,judd1 ,quart4 ,jour4 ,geol4 ,soc41 vol4 xxx4 p4 #bdb4 #d ,history of ,volcanic ,action1 etc41 loc4 cit4 p4 #aec1 et seq4 ,the ,granophyres of ,geikie come under the head of ,felsites1 passing into granite in one direction and quartz-trachyte in another1 according to ,judd2 the proportion of silica from #fi to #ge per cent4--,quart4 ,jour4 ,geol4 ,soc41 vol4 xxx4 p4 #bce4 #e ,this view the author has expressed in a recent edition of ,the ,physical ,geology of ,ireland1 p4 #agg 7#ahia74 ,,chapter ,,iv4 ,,isle ,,of ,,skye4 ,this is the largest and most important of all the ,tertiary volcanic districts1 but owing to the extensive denudation to which1 in common with other ,tertiary volcanic regions of the ,british ,isles1 it has been subjected1 its present limits are very restricted comparatively to its original extent4 ,not only is this evident from the manner in which the basaltic sheets terminate along the sea-coast in grand mural cliffs1 as opposite ,macleod's ,maidens1 and at the entrance to ,lough ,bracadale on the western coast1 but the evidence is1 according to ,sir ,a4 ,geikie1 still more striking along the eastern coast2 showing that the ,jurassic1 and other older rocks there visible1 were originally buried deep under the basaltic sheets which have been stripped from off that part of the country4 ,these great plateau-basalts occupy about three-fourths of the entire island along the western and northern areas1 rising into terraced mountains over #b1jjj feet in height1 and are deeply furrowed by glens and arms of the sea1 along which the general structure of the tableland is laid open1 sometimes for leagues at a time4 ,it is towards the south-eastern part of the island that the most interesting and important phenomena are centred2 for here we meet with representatives of the acid 7or highly silicated7 group of rocks1 and of remarkable beds of gabbro1 which have long attracted the attention of petrologists4 ,these latter beds1 throughout a considerable distance round the flanks of the ,cuillin ,hills1 are interposed between the acid rocks and the plateau-basalts2 but towards the north1 on approaching ,lough ,sligahan1 the acid rocks1 consisting of granophyres1 quartz-porphyries1 and hornblendic-granitites1 are in direct contact with the plateau-basalts2 and1 according to the very circumstantial account of ,sir ,a4 ,geikie1 are intrusive into them2 not only sending veins into the basaltic sheets1 but also producing a marked alteration in their structure where they approach the newer intrusive mass4 ,equally circumstantial is the same author's account of the relations of the granophyres to the gabbros1#a as seen at ,meall ,dearg and the western border of the ,cuillin ,hills--where the former rock may be seen to send numerous veins into the latter4 ,not only is this so1 but the granophyre is frequently seen to truncate1 and abruptly terminate some of the basaltic dykes by which the basic sheets are traversed--as in the neighbourhood of ,beinn na ,dubhaic4 ,all these phenomena strongly remind us of the conditions of similar rocks amongst the mountains of ,mourne and ,carlingford in ,ireland2 where1 at ,barnaveve1 the syenite 7or hornblendic quartz-felsite7 is seen to break through the masses of olivine gabbro1 and send numerous veins into this latter rock4#b ,the interpretation here briefly sketched differs widely from that arrived at by ,professor ,judd4 ,the granitoid masses of the ,red ,mountains 7,beinn ,dearg7 and the neighbouring heights are1 in his view1 the roots of the great volcano from which were erupted the various lavas2 the earlier eruptions producing the acid lavas1 to be followed by the gabbros1 and these by the plateau-basaltic sheets1 which stretch away towards the north and west into several peninsulas4 ,thus he holds that the rocks of basic composition were ejected subsequently to those of the acid variety1 and appeals to various sections in confirmation of this view4#c ,to reconcile these views is at present impossible2 but as the controversy between these two observers is probably not yet closed1 there is room for hope that the true interpretation of the relations of these rocks to each other will ere long be fully established4 #a ,geikie1 loc4 cit41 p4 #afa1 etc4 #b ,physical ,geology of ,ireland1 #bnd edition1 p4 #agd 7,fig4 #ba74 ,professor ,judd has also come to the conclusion that the granite of ,mourne is of ,tertiary age1 ,quart4 ,jour4 ,geol4 ,soc41 vol4 xxx4 p4 #bge4 #c ,judd1 loc4 cit41 p4 #bed4 ,,chapter ,v4 ,,the ,,scuir ,,of ,,eigg4 ,amongst the more remarkable of the smaller islets are those of ,eigg1 ,rum1 ,canna1 and ,muck1 lying between ,mull on the south and ,skye on the north1 and undoubtedly at one time physically connected together4 ,the ,island of ,eigg is especially remarkable for the fact1 as stated by ,geikie1 that here we have the one solitary case of a true superficial stream of acid lava--that of the ,scuir of ,eigg4#a 7,fig4 #cd47 ,this forms a sinuous ridge1 composed of pitchstone of several kinds1 of over two miles in length1 rising from the midst of a tableland of bedded basalt and tuff to a height of #a1bhi feet above the ocean2 the plateau-basalt is traversed by basaltic dykes1 ranging in a ,n4,w4-,s4,e4 direction4 ,but what is specially remarkable is the evidence afforded by an examination of the course of the ,scuir1 that it follows the channel of an ancient river-valley1 which has been hollowed out in the surface of the plateau4 ,the course of this channel is indicated by the presence of a deposit of river-gravel1 which in some places forms a sort of cushion between the base of the ,scuir and the side of the channel4 ,over this gravel-bed the viscous pitchstone-lava appears to have flowed1 taking possession of the river-channel1 and also of the beds of several small tributary streams which flowed into the channel of the ,scuir4 ,the recent date of the pitchstone forming this remarkable mural ridge1 once occupying the bed of a river-channel1 is shown by the fact that the basaltic dykes which traverse the plateau-basalts are truncated by the river-gravel1 which is1 therefore1 more recent2 and1 as we have seen1 the pitchstone stream is more recent than the river-gravel4 ,but at the time when this last volcanic eruption took place1 the physical geography of the whole region must have been very different from that of the present time4 ,from the character and composition of the pebbles in the old river-bed1 amongst which are ,cambrian sandstone1 quartzite1 clay-slate1 and white ,jurassic limestone1 ,sir ,a4 ,geikie concludes that when the river was flowing1 the island must have been connected with the mainland to the east where the parent masses of these pebbles are found4 ,illustration3 ,fig4 #cd4--,view of the ,scuir of ,eigg from the east4 ,the lower portion of the mountain is formed of bedded basalt1 or dolerite with numerous dykes and veins of basalt1 felstone1 and pitchstone2 the upper cliff1 or ,scuir1 is composed of pitchstone of newer age1 the remnant of a lava flow which once filled a river channel in the basaltic sheets4 ,a dyke1 or sheet1 of porphyry is seen to be interposed between the ,scuir and the basaltic sheets4--7,after ,geikie47 ,effects of ,denudation4--,the position of the ,scuir of ,eigg and its relations to the basaltic sheets show the enormous amount of denudation which these latter have undergone since the stream of pitchstone-lava filled the old river channel4 ,the walls1 or banks1 of the channel have been denuded away1 thus converting the pitchstone casting into a projecting wall of rock4 ,that it originally extended outwards into the ocean to a far greater distance than at present is evident from the abruptly truncated face of the cliff2 and yet this remarkable volcanic mass seems to have been1 perhaps1 the most recent exhibition of volcanic action to be found in the ,british ,isles4 ,it is perhaps1 on this account1 the most striking of the numerous examples exhibited throughout the ,west of ,scotland and the ,north-east of ,ireland of the enormous amount of denudation to which these districts have been subjected since the extinction of the volcanic fires2 and this at a period to which we cannot assign a date more ancient than that of the ,pliocene4 ,yet1 let us consider for a moment to what physical vicissitudes these districts have been subjected since that epoch4 ,assuming1 as we may with confidence1 that the volcanic eruptions were subarial1 and that the tracts covered by the plateau-basalts were in the condition of dry land when the eruptions commenced1 in this condition they continued in the main throughout the period of volcanic activity4 ,but the eruptions had scarcely ceased1 and the lava floods and dykes become consolidated1 before the succeeding glacial epoch set in2 when the snows and glaciers of the ,scottish ,highlands gradually descending from their original mountain heights1 and spreading outwards in all directions1 ultimately enveloped the whole of the region we are now considering until it was entirely concealed beneath a mantle of ice moving slowly1 but irresistibly1 outwards towards the ,atlantic1 crossing the deep channels1 such as the ,sound of ,mull and the ,minch1 climbing up the sides of opposing rocks and islands until even the ,outer ,hebrides and the ,north-east of ,ireland were covered by one vast mantle of ice and snow4 ,the movement of such a body of ice over the land must have been attended with a large amount of abrasion of the rocky floor2 nor have the evidences of that abrasion entirely disappeared even at the present day4 ,we still detect the grooves and scorings on the rock-surfaces where they have been protected by a coating of boulder clay2 and we still find the surface strewn with the blocks and dbris of that mighty ice-flood4 ,but whatever may have been the amount of erosion caused by the great ice-sheet1 it was chiefly confined to the more or less horizontal surface-planes4 ,erosion of another kind was to succeed1 and to produce more lasting effects on the configuration of the surface4 ,on the disappearance of the ice-sheet1 an epoch characterised by milder conditions of climate set in4 ,this was accompanied by subsidence and submersion of large tracts of the land during the ,interglacial stage2 so that the sea rose to heights of several hundred feet above the present level1 and has left behind stratified gravels with shells at these elevations in protected places4 ,during this period of depression and of subsequent re-emergence the wave-action of the ,atlantic waters must have told severely on the coast and islands1 wearing them into cliffs and escarpments1 furrowing out channels and levelling obstructions4 ,such action has gone on down to the present day4 ,the ,north-west of ,scotland and of ,ireland has been subjected throughout a very lengthened period to the wear and tear of the ,atlantic billows4 ,in the case of the former1 the remarkable breakwater which nature has thrown athwart the ,north-west ,highlands in the direction of the waves1 forming the chain of islands constituting the ,outer ,hebrides1 and composed of very tough ,archan gneiss and schist1 has done much to retard the inroads which the waves might otherwise have made on the ,isle of ,skye2 while ,coll and ,tiree1 composed of similar materials1 have acted with similar beneficent effect for ,mull and the adjoining coasts4 ,but such is the tremendous power of the ,atlantic billows when impelled by westerly winds1 that to their agency must be mainly attributed the small size of the volcanic land-surfaces as compared with their original extent1 and the formation of those grand headlands which are presented by the igneous masses of ,skye1 ,ardnamurchan1 and ,mull towards the west4 ,rain and river action1 supplemented by that of glaciers1 have also had a share in eroding channels and wearing down the upper surface of the ground1 with the result we at present behold in the wild and broken scenery of the ,inner ,hebrides and adjoining coast4 #a ,geikie1 loc4 cit41 p4 #agh2 also ,quart4 ,jour4 ,geol4 ,soc41 vol4 xxvii4 p4 #cjc4 ,,chapter ,,vi4 ,,isle ,,of ,,staffa4 ,reference has been made to this remarkable island in a former page1 but some more extended notice is desirable before leaving the region of the ,inner ,hebrides4 ,along with the islands of ,pladda1 ,treshnish1 and ,blackmore1 ,staffa is one of the outlying volcanic islands of the group1 being distant about six miles from the coast of ,mull1 and indicates the minimum distance to which the plateau-basaltic sheets originally extended in the direction of the old marginal lands of ,tiree and ,coll4 ,the island consists of successive sheets of bedded basaltic lava1 with partings of tuff1 one of which of considerable thickness is shown to lie at the base of the cliff on the south-west side of the island4#a ,the successive lava-sheets present great varieties of structure1 like those on the north coast of ,antrim2 some being amorphous1 others columnar1 with either straight or bent columns4 ,the lava-sheet out of which ,fingal's ,cave is excavated consists of vertical prisms1 beautifully formed1 and surmounted by an amorphous mass of the same material4 ,at the entrance of the ,boat ,cave we have a somewhat similar arrangement of the columns2#b but at the ,clam-shell ,cave the prisms are curved1 indicating some movement in the viscous mass before they had been fully consolidated4 ,fingal's ,cave is called after the celebrated prince of ,morvern 7or ,morven71 a province of ancient ,caledonia4 ,he is supposed to have been the father of ,ossian1 the ,celtic bard rendered famous by ,macpherson4 ,the cave1 one of many which pierce the coast-cliffs of ,western ,scotland1 is #bbg feet in length1 #aff feet in height1 and #dj feet in width4 ,on all sides regular columns of basalt1 some entire1 others broken1 rise out of the water and support the roof4 ,the cave is only accessible in calm weather4 #a ,a drawing of this cliff is given by ,geikie in the ,manual of ,geology 7,jukes and ,geikie71 #crd edition1 p4 #bgg4 #b ,prestwich1 ,geology1 vol4 i4 p4 #bha1 where a view of this cave is given4 ,,part ,v4 ,,pre-,,tertiary ,,volcanic ,,rocks4 ,,chapter ,i4 ,,the ,,deccan ,,trap-,,series ,,of ,,india4 ,the great outpourings of augitic lava of ,tertiary and recent times which we have been considering appear to have been anticipated in several parts of the world1 more especially in ,peninsular ,india and in ,africa1 and it is desirable that we should devote a few pages to the description of these remarkable volcanic formations1 as they resemble1 both in their mode of occurrence and general structure1 some of the great lava-floods of a more recent period we have been considering4 ,of the districts to be described1 the first which claims our notice is the ,deccan4 7a47 ,extent of the ,volcanic ,plateau4--,the volcanic plateau of the ,deccan stretches from the borders of the ,western ,ghats and the sea-coast near ,bombay inland to ,amarantak1 at the head of the ,narbudda ,river 7long4 #hb ,e471 and from ,belgaum 7lat4 #ae #ca' ,n47 to near ,goona 7lat4 #bd #cj'74 ,the vast area thus circumscribed is far from representing the original extent of the tract overspread by the lava-floods1 as outlying fragments of these lavas are found as far east as long4 #hd ,e4 in one direction1 and at ,kattiwar and ,cutch in another4 ,the present area1 however1 is estimated to be not less than #bjj1jjj square miles4#a 7b47 ,nature and ,thickness of the ,lava-flows4--,this tract is overspread almost continuously by sheets of basaltic lava1 with occasional bands of fresh-water strata containing numerous shells1 figured and described by ,hislop1 and believed by him to be of ,lower ,eocene age4 ,the lava-sheets vary considerably in character1 ranging from finest compact basalt to coarsely crystalline dolerite1 in which olivine is abundant4 ,the columnar structure is not prevalent1 the rock being either amorphous1 or weathering into concentric shells4 ,volcanic ash1 or bole1 is frequently found separating the different lava-flows2 and in the upper amygdaloidal sheets numerous secondary minerals are found1 such as quartz1 agate and jasper1 stilbite and chlorite4 ,the total thickness of the whole series1 where complete1 is about #f1jjj feet1 divided as follows3 #a4 ,upper trap2 with ash and inter-trappean beds #a1ejj feet #b4 ,middle trap2 sheets of basalt and ash #d1jjj #c4 ,lower trap2 basalt with inter-trappean beds #ejj -------- #f1jjj ,throughout the region here described these great sheets of volcanic rock are everywhere approximately horizontal1 and constitute a table-land of #c1jjj to #d1jjj feet in elevation1 breaking off in terraced escarpments1 and penetrated by deep river-valleys1 of which the ,narbudda is the most important4 ,the foundation rock is sometimes metamorphic schist1 or gneiss1 at other times sandstone referred by ,hislop to ,jurassic age2 and in no single instance has a volcanic crater or focus of eruption been observed4 ,but outside the central trappean area volcanic foci are numerous1 as in ,cutch1 the ,rajhipla ,hills and the ,lower ,narbudda valley4 ,the original excessive fluidity of the ,deccan trap is proved by the remarkable horizontality of the beds over large areas1 and the extensive regions covered by very thin sheets of basalt or dolerite4 7c47 ,geological ,age4--,as regards the geological age of this great volcanic series much uncertainty exists1 owing to the absence of marine forms in the inter-trappean beds4 ,one single species1 ,cardita variabilis1 has been observed as occurring in these beds1 and in the limestone below the base of the trap at ,dudukur4 ,the facies of the forms in this limestone is ,tertiary2 but there is a remarkable absence of characteristic genera4 ,on the other hand1 ,mr4 ,blanford states that the bedded traps are seen to underlie the ,eocene ,tertiary strata with ,nummulites in ,guzerat and ,cutch1#b which would appear to determine the limit of their age in one direction4 ,on balancing the evidence1 however1 it is tolerably clear that the volcanic eruptions commenced towards the close of the ,cretaceous period1 and continued into the commencement of the ,tertiary1 thus bridging over the interval between the two epochs2 and since the greater sheets have been exposed throughout the whole of the ,tertiary and ,quarternary periods1 it is not surprising if they have suffered enormously from denuding agencies1 and that any craters or cones of eruption that may once have existed have disappeared4 #a ,the ,deccan ,traps have been described by ,sykes1 ,geol4 ,trans41 #bnd ,series1 vol4 iv42 also ,rev4 ,s4 ,hislop1 ,on the ,geology of the ,neighbourhood of ,nagpur1 ,central ,india1 ,quart4 ,journ4 ,geol4 ,soc41 vol4 x4 p4 #bgd2 and ,ibid41 vol4 xvi4 p4 #aed4 ,also1 ,h4 ,b4 ,medlicott and ,w4 ,t4 ,blanford1 ,manual of the ,geology of ,india1 vol4 i4 7#ahgi74 #b ,blanford1 ,geology of ,abyssinia1 p4 #ahe4 ,,chapter ,,ii4 ,,abyssinian ,,table-,,lands4 ,another region in which the volcanic phenomena bear a remarkable analogy to those of ,central ,india1 just described1 is that of ,abyssinia4 ,nor are these tracts so widely separated that they may not be considered as portions of one great volcanic area extending from ,abyssinia1 through ,southern ,arabia1 into ,cutch and the ,deccan1 in the one direction1 while the great volcanic cones of ,kenia and ,kilimanjaro1 with their surrounding tracts of volcanic matter1 may be the extreme prolongations in the other4 ,along this tract volcanic operations are still active in the ,gulf of ,aden2 and cones quite unchanged in form1 and evidently of very recent date1 abound in many places along the coast both of ,arabia and ,africa4 ,the volcanic formations of this tract are1 however1 much more recent than those which occupy the high plateaux of ,central and ,southern ,abyssinia of which we are about to speak4 7a47 ,physical ,features4--,abyssinia forms a compact region of lofty plateaux intersected by deep valleys1 interposed between the basin of the ,nile on the west1 and the low-lying tract bordering the ,red ,sea and the ,indian ,ocean on the east4 ,the plateaux are deeply intersected by valleys and ravines1 giving birth to streams which feed the head waters of the ,blue ,nile 7,bahr el ,arak7 and the ,atbara4 ,several fine lakes lie in the lap of the mountains1 of which the ,zana1 or ,dembia1 is the largest1 and next ,ashangi1 visited by the ,british army on its march to ,magdala in #ahfh1 and which1 from its form and the volcanic nature of the surrounding hills1 appears to occupy the hollow of an extinct crater4 ,the table-land of ,abyssinia reaches its highest elevation along the eastern and southern margin1 where its average height may be #h1jjj to #aj1jjj feet2 but some peaks rise to a height of #ab1jjj to #ae1jjj feet in ,shoa and ,ankobar4#a 7b47 ,basaltic ,lava ,sheets4--,an enormous area of this country seems to be composed of volcanic rocks chiefly in the form of sheets of basaltic lava1 which rise into high plateaux1 and break off in steep--sometimes precipitous--mural escarpments along the sides of the valleys4 ,these are divisible into the following series3-- 7#a7 ,the ,ashangi ,volcanic ,series4--,the earliest forerunners of the more recent lavas seem to have been erupted in ,jurassic times1 in the form of sheets of contemporaneous basalt or dolerite amongst the ,antola limestones which are of this period4 ,but the great mass of the volcanic rocks are much more recent1 and may be confidently referred to the late ,cretaceous or early ,tertiary epochs4 ,their resemblance to the great trappean series of ,western ,india1 even in minute particulars1 is referred to by ,mr4 ,blanford1 who suggests the view that they belong to one and the same great series of lava-flows extruded over the surface of this part of the globe4 ,this view is inherently probable4 ,they consist of basalts and dolerites1 generally amygdaloidal1 with nodules of agate and zeolite1 and are frequently coated with green-earth 7chlorite74 ,beds of volcanic ash or breccia also frequently occur1 and often contain augite crystals4 ,at ,senaf1 hills of trachyte passing into claystone and basalt were observed by ,mr4 ,blanford1 but it is not clear what are their relations to the plateau-basaltic sheets4#b 7#b7 ,magdala ,volcanic ,series4--,this is a more recent group of volcanic lavas1 chiefly distinguished from the lower1 or ,ashangi1 group1 by the occurrence of thick beds of trachyte1 usually more or less crystalline1 and containing beautiful crystals of sanidine4 ,the beds of trachyte break off in precipitous scarps1 and being of great thickness and perfectly horizontal1 are unusually conspicuous4 ,mr4 ,blanford says1 with regard to this group1 that there is a remarkable resemblance in its physical aspect to the scenery of the ,deccan and the higher valleys of the ,western ,ghats of ,india1 but the peculiarities of the landscape are exaggerated in ,abyssinia4 ,many of the trachytic beds are brecciated and highly columnar2 sedimentary beds are also interstratified with those of volcanic origin4 ,the ,magdala group is unconformable to that of ,ashangi in some places4 ,a still more recent group of volcanic rocks appears to occur in the neighbourhood of ,senaf1 consisting of amorphous masses of trachyte1 often so fine-grained and compact as to pass into claystone and to resemble sandstone4 ,at ,akub ,teriki the rocks appear to be in the immediate vicinity of an ancient vent of eruption4 ,from what has been said1 it will be apparent that ,abyssinia offers volcanic phenomena of great interest for the observer4 ,there is considerable variety in the rock masses1 in their mode of distribution1 and in the scenery which they produce4 ,the extensive horizontal sheets of lava are suggestive of fissure-eruption rather than of eruption through volcanic craters2 and although these may have once been in existence1 denudation has left no vestiges of them at the present day4 ,in all these respects the resemblance of the volcanic phenomena to those of ,peninsular ,india is remarkably striking2 it suggests the view that they are contemporaneous as regards the time of their eruption1 and similar as regards their mode of formation4 #a ,w4 ,t4 ,blanford1 ,geology of ,abyssinia1 pp4 #aea-b4 #b ,blanford1 loc4 cit41 p4 #ahb4 ,,chapter ,,iii4 ,,cape ,,colony4 ,basalt of the ,plateau4--,the extensive sheets of plateau-basalt forming portions of the ,neuweld range and the elevated table-land of ,cape ,colony1 may be regarded as forerunners of those just described1 and possibly contemporaneous with the ,ashangi volcanic series of ,abyssinia4 ,the great basaltic sheets of the ,cape ,colony are found capping the highest elevations of the ,camderboo and ,stormberg ranges1 as well as overspreading immense areas of less elevated land1 to an extent1 according to ,professor ,a4 ,h4 ,green1 of at least #abj1jjj square miles4#a ,amongst these sheets1 innumerable dykes1 and masses of solid lava which filled the old vents of eruption1 are to be observed4 ,the floor upon which the lava-floods have been poured out generally consists of the ,cave ,sandstone1 the uppermost of a series of deposits which had previously been laid down over the bed of an extensive lake which occupied this part of ,africa during the ,mesozoic period4 ,after the deposition of this sandstone1 the volcanic forces appear to have burst through the crust1 and from vents and fissures great floods of augitic lava1 with beds of tuff1 invaded the region occupied by the waters of the lake4 ,the lava-sheets have since undergone extensive denudation1 and are intersected by valleys and depressions eroded down through them into the sandstone floor beneath2 and though the precise geological period at which they were extruded must remain in doubt1 it appears probable that they may be referred to that of the ,trias4#b #a ,green4 ,on the ,geology of the ,cape ,colony1 ,quart4 ,jour4 ,geol4 ,soc41 vol4 xliv4 7#ahhh74 #b ,the district lying along the south coast of ,africa is described by ,andrew ,g4 ,bain1 in the ,trans4 ,geol4 ,soc41 vol4 vii4 7#ahde72 but there is little information regarding the volcanic region here referred to4 ,,chapter ,,iv4 ,,volcanic ,,rocks ,,of ,,past ,,geological ,,periods ,,of ,,the ,,british ,,isles4 ,it is beyond the scope of this work to describe the volcanic rocks of pre-,tertiary times over various parts of the globe4 ,the subject is far too large to be treated otherwise than in a distinct and separate essay4 ,i will therefore content myself with a brief enumeration of the formations of the ,british ,isles in which contemporaneous volcanic action has been recognised4#a ,there is little evidence of volcanic action throughout the long lapse of time extending backwards from the ,cretaceous to the ,triassic epochs1 that is to say1 throughout the ,mesozoic or ,secondary period1 and it is not till we reach the ,palozoic strata that evidence of volcanic action unmistakably presents itself4 ,permian ,period4--,in ,ayrshire1 and in the western parts of ,devonshire1 beds of felspathic porphyry1 felstone and ash are interstratified with strata believed to be of ,permian age4 ,in ,devonshire these have only recently been recognised by ,dr4 ,irving and the author as of ,permian age1 the strata consisting of beds of breccia1 lying at the base of the ,new ,red ,sandstone4 ,those of ,ayrshire have long been recognised as of the same period2 as they rest unconformably on the coal measures1 and consist of porphyrites1 melaphyres1 and tuffs of volcanic origin4 ,carboniferous ,period4--,volcanic rocks occur amongst the coal-measures of ,england and ,scotland1 while they are also found interbedded with the ,carboniferous ,limestone series in ,derbyshire1 ,scotland1 and ,co4 ,limerick in ,ireland4 ,the rocks consist chiefly of basalt1 dolerite1 melaphyre and felstone4 ,devonian ,period4--,volcanic rocks of ,devonian age occur in the ,south of ,scotland1 consisting of felstone-porphyries and melaphyres2 also at ,boyle1 in ,roscommon1 and amongst the ,glengariff beds near ,killarney in ,ireland4 ,upper ,silurian ,period4--,volcanic rocks of this stage are only known in ,ireland1 on the borders of ,cos4 ,mayo and ,galway1 west of ,lough ,mask1 and at the extreme headland of the ,dingle ,promontory in ,co4 ,kerry4 ,they consist of porphyrites1 felstones and tuffs1 or breccias1 contemporaneously erupted during the ,wenlock and ,ludlow stages4 ,around the flanks of ,muilrea1 beds of purple quartz-felstone with tuff are interstratified with the ,upper ,silurian grits and slates4 ,lower ,silurian ,period4--,volcanic action was developed on a grand scale during the ,arenig and ,caradoc-,bala stages1 both in ,wales and the ,lake district1 and in the ,llandeilo stage in the ,south of ,scotland4 ,the felspathic lavas1 with their associated beds of tuff and breccia1 rise into some of the grandest mountain crests of ,north ,wales1 such as those of ,cader ,idris1 ,aran ,mowddwy1 ,arenig and ,moel ,wyn4 ,a similar series is also represented in ,ireland1 ranging from ,wicklow to ,waterford1 forming a double group of felstones1 porphyries1 breccias1 and ash-beds1 with dykes of basalt and dolerite4 ,the same series again appears amidst the ,lower ,silurian beds of ,co4 ,louth1 near ,drogheda4 ,metamorphic ,series presumably of ,lower ,silurian ,age4--,if1 as seems highly probable1 the great metamorphic series of ,donegal and ,derry are the representatives in time of the ,lower ,silurian series1 some of the great sheets of felspathic and hornblendic trap which they contain are referable to this epoch4 ,these rocks have undergone a change in structure along with the sedimentary strata of which they were originally formed1 so that the sheets of 7presumably7 augitic lava have been converted into hornblende-rock and schist4 ,similar masses occur in ,north ,mayo1 south of ,belderg ,harbour4 ,cambrian ,period4--,in the ,pass of ,llanberis1 along the banks of ,llyn ,padarn1 masses of quartz-porphyry1 felsite and agglomerate1 or breccia1 indicate volcanic action during this stage4 ,these rocks underlie beds of conglomerate1 slate and grit of the ,lower ,cambrian epoch1 and1 as ,mr4 ,blake has shown1 are clearly of volcanic origin1 and pass upwards into the sedimentary strata of the period4 ,a similar group1 first recognised by ,professor ,sedgwick1 stretches southwards from ,bangor along the southern shore of the ,menai ,straits4 ,again1 we find the volcanic eruptions of this epoch at ,st4 ,david's1 consisting of diabasic and felsitic lava1 with beds of ash2 and in the centre of ,england1 amongst the grits and slates of ,charnwood ,forest presumably of ,cambrian age1 various felstones1 porphyries1 and volcanic breccias are found4 ,thus it will be seen that every epoch1 from the earliest stage of the ,cambrian to the ,permian1 in the ,british ,isles1 gives evidence of the existence of volcanic action2 from which we may infer that the originating cause1 whatever it may be1 has been in operation throughout all past geological time represented by living forms4 ,the question of the condition of our globe in ,archan times1 and earlier1 is one which only can be discussed on theoretic ground1 and is beyond the scope of this work4 #a ,the reader is referred to ,sir ,a4 ,geikie's ,presidential ,address to the ,geological ,society 7#ahia7 for the latest view of this subject4 ,illustration3 ,,volcanic ,,band ,,of ,,the ,,moluccas4 ,map showing the volcanic belt to which ,krakatoa belongs4 ,the shaded portion is volcanic4 ,,part ,,vi4 ,,special ,,volcanic ,,and ,,seismic ,,phenomena4 ,,chapter ,i4 ,,the ,,eruption ,,of ,,krakatoa ,,in #ahhc4 ,i propose to introduce here some account of one of the most terrible outbursts of volcanic action that have taken place in modern times2 namely1 the eruption of the volcano of ,krakatoa 7a corruption of ,rakata7 in the strait of ,sunda1 between the islands of ,sumatra and ,java1 in the year #ahhc4 ,the ,malay ,archipelago1 of which this island once formed a member1 is a region where volcanic action is constant1 and where the outbursts are exceptionally violent4 ,with the great island of ,borneo as a solid1 non-volcanic central core1 a line of volcanic islands extends from ,chedooba off the coast of ,pegu through ,sumatra1 ,java1 ,sumbawa1 ,flores1 and1 reaching the ,moluccas1 stretches northwards through the ,philippines into ,japan and ,kamtschatka4 ,this is probably the most active volcanic belt in the world1 and the recent terrible earthquake and eruption in ,japan 7,november1 #ahia7 gives proof that the volcanic forces are as powerful and destructive as ever4#a 7a47 ,dormant ,condition down to #afhj4--;,down to the year #afhj1 this island1 although from its form and structure evidently volcanic1 appears to have been in a dormant state2 its sides were covered with luxuriant forests1 and numerous habitations dotted its shore4 ,but in ,may of that year an eruption occurred1 owing to which the aspect of ,krakatoa as described by ,vogel was entirely changed2 the surface of the island when this writer passed on his voyage to ,sumatra appeared burnt up and arid1 while blocks of incandescent rock were being hurled into the air from four distinct points4 ,after this first recorded eruption the island relapsed into a state of repose1 and except for a stream of molten lava which issued from the northern extremity1 there was no evidence of its dangerous condition4 ,the luxuriant vegetation of the tropics speedily re-established itself1 and the volcano was generally regarded as extinct4#b ,history repeats itself2 and the history of ,vesuvius was repeated in the case of ,krakatoa4 ,illustration3 ,fig4 #ce4--,map ,of ,the ,krakatoa ,group ,of ,islands ,before ,the ,eruption ,of ,august #ahhc 7,from ,admiralty ,chart7 7b47 ,eruption of ,may1 #ahhc4c--,on the morning of ,may #bj1 #ahhc1 the inhabitants of ,batavia1 of ,buitenzorg1 and neighbouring localities1 were surprised by a confused noise1 mingled with detonations resembling the firing of artillery4 ,the phenomena commenced between ten and eleven o'clock in the morning1 and soon acquired such intensity as to cause general alarm4 ,the detonations were accompanied by tremblings of the ground1 of buildings and various objects contained in dwellings2 but it was generally admitted that these did not proceed from earthquake shocks1 but from atmospheric vibrations4 ,no deviation of the magnetic needle was observed at the ,meteorological ,institute of ,batavia2 but a vertical oscillation was apparent1 and persons who listened with the ear placed on the ground1 even during the most violent detonations1 could hear no subterranean noise whatever4 ,it became clear that the sounds came from some volcano burst into activity2 but it is strange that for two whole days it remained uncertain what was the particular volcano to which the phenomena were to be referred4 ,the detonations appeared1 indeed1 to come from the direction of ,krakatoa2 but from ,serang1 ,anjer1 and ,merak1 localities situated much nearer ,krakatoa than ,batavia1 the telegraph announced that neither detonations nor atmospheric vibrations had been perceived4 ,the distance between ,batavia and ,krakatoa is ninety-three ,english miles4 ,the doubts thus experienced were1 however1 soon put to rest by the arrival of an ,american vessel under the command of ,a4 ,r4 ,thomas1 and of other ships which hailed from the straits of ,sunda4 ,from their accounts it was ascertained that in the direction of ,krakatoa the heavens were clouded with ashes1 and that a grand column of smoke1 illumined from time to time by flashes of flame1 arose from above the island4 ,thus after a repose of more than two hundred years1 the peaceable isle of ,krakatoa1 inhabited1 and covered by thick forests1 was suddenly awakened from its condition of fancied security4 ,illustration3 ,fig4 #cf4--,section from ,verlaten ,island through ,krakatoa1 to show the outline before and after the eruption of ,august1 #ahhh4 ,the continuous line shows the former2 the dotted line and shading1 the latter2 from which it will be observed that the original island has to a large extent disappeared4 ,the line of section is shown in ,fig4 #ce4 7c47 ,form and ,appearance of the ,island before the ,eruption of #ahhc4--;,from surveys made in #ahdi and #ahha1 it would appear that the island of ,krakatoa consisted of three mountains or groups of mountains 7,figs4 #ce1 #cf72 the southern formed by the cone of ,rakata 7properly so called71 rising with a scarped face above the sea to a height of over #hjj mtres 7#b1fbb feet74 ,adjoining this cone1 and rising from the centre of the island1 came the group of ,danan1 composed of many summits1 probably forming part of the enceinte annulaire of a crater4 ,and near the northern extremity of the isle1 a third group of mammelated heights could be recognised under the general name of ,perboewatan1 from which issued several obsidian lava-flows1 with a steep slope2 these dated back perhaps to the period of the first known eruption of #afhj4 ,this large and mountainous island as it existed at the beginning of ,may1 #ahhc1 has been entirely destroyed by the terrible eruptions of that year1 with the exception of the peripheric rim 7composed of the most ancient of the volcanic rocks1 andesite71 of which ,verlaten ,island and ,rakata formed a part1 and one very small islet1 which is noted on the maps as rots 7rock71 and on the new map of the ,straits of ,sunda of the ,dutch ,navy as that of ,bootsmansrots4#d ,as shown by the map in the ,report of the ,royal ,society1 the group of islands which existed previous to #ahhc were but the unsubmerged portions of one vast volcanic crater1 built up of a remarkable variety of lava allied to the andesite of the ,java volcanoes1 but having a larger percentage of silica1 and hence falling under the head of enstatite-dacite4#e ,that these volcanic rocks are of very recent origin is shown by the fact1 ascertained by ,verbeek1 that beneath them occur deposits of ,post-,tertiary age1 and that these in turn rest on the ,tertiary strata which are widely distributed through ,sumatra1 ,java1 and the adjoining islands4 ,according to the reasoning of ,professor ,judd1 the ,krakatoa group at an early period of its history presented the form of a magnificent crater-cone1 several miles in circumference at the base1 which subsequent eruptions shattered into fragments or blew into the air in the form of dust1 ashes1 and blocks of lava1 while the central part collapsed and fell in1 leaving a vast circular ring like the ancient crater of ,somma 7see ,fig4 #f1 p4 #dc71 and he supposes the former eruptions to have been on a scale exceeding in magnificence those which have caused such world-wide interest within the last few years4 7d47 ,eruption of #bfth to #bhth of ,august4--,it was1 as we have seen1 in the month of ,may that1 in the language of ,chev4 ,verbeek1 the volcano of ,krakatoa chose to announce in a high voice to the inhabitants of the ,archipelago that1 although almost nothing amongst the many colossal volcanic mountains of the ,indies1 it yielded to none of them in regard to its power4 ,these eruptions were1 however1 only premonitory of the tremendous and terrible explosion which was to commence on ,sunday1 the #bfth of ,august1 and which continued for several days subsequently4 ,a little after noon of that day1 a rumbling noise accompanied by short and feeble explosions was heard at ,buitenzorg1 coming from the direction of ,krakatoa2 and similar sounds were heard at ,anjer and ,batavia a little later4 ,soon these detonations augmented in intensity1 especially about five o'clock in the evening2 and news was afterwards received that the sounds had been heard in the isle of ,java4 ,these sounds increased still more during the night1 so that few persons living on the west side of the isle of ,java were able to sleep4 ,at seven in the morning there came a crash so formidable1 that those who had hoped for a little sleep at ,buitenzorg leaped from their beds4 ,meanwhile the sky1 which had up to this time been clear1 became overcast1 so that by ten o'clock it became necessary to have recourse to lamps1 and the air became charged with vapour4 ,occasional shocks of earthquake were now felt4 ,darkness became general all over the straits and the bordering coasts4 ,showers of ashes began to fall4 ,the repeated shocks of earthquake1 and the rapid discharges of subterranean artillery1 all combined to show that an eruption of even greater violence than that of ,may was in progress at the isle of ,krakatoa4 ,but the most interested witnesses to this terrible outburst were those on board the ships plying through the straits4 ,amongst these was the ,charles ,bal1 a ,british vessel under the command of ,captain ,watson4 ,this ship was ten miles south of the volcano on ,sunday afternoon1 and therefore well in sight of the island at the time when the volcano had entered upon its paroxysmal state of action4 ,captain ,watson describes the island as being covered by a dense black cloud1 while sounds like the discharges of artillery occurred at intervals of a second of time2 and a crackling noise 7probably arising from the impact of fragments of rock ascending and descending in the atmosphere7 was heard by those on board4 ,these appearances became so threatening towards five o'clock in the evening1 that the commander feared to continue his voyage and began to shorten sail4 ,from five to six o'clock a rain of pumice in large pieces1 quite warm1 fell upon the ship1 which was one of those that escaped destruction during this terrible night4#f 7e47 ,electrical ,phenomena4--,during this eruption1 electrical phenomena of great splendour were observed4 ,captain ,wooldbridge1 viewing the eruption in the afternoon of the #bfth from a distance of forty miles1 speaks of a great vapour-cloud looking like an immense wall being momentarily lighted up by bursts of forked lightning like large serpents rushing through the air4 ,after sunset this dark wall resembled a blood-red curtain1 with edges of all shades of yellow1 the whole of a murky tinge1 through which gleamed fierce flashes of lightning4 ,as ,professor ,judd observes1 the abundant generation of atmospheric electricity is a familiar phenomenon in all volcanic eruptions on a grand scale4 ,the steam-jets rushing through the orifices of the earth's crust constitute an enormous hydro-electrical engine1 and the friction of the ejected materials striking against one another in their ascent and descent also does much in the way of generating electricity4#g ,it has been estimated by several observers that the column of watery vapour ascended to a height of from twelve to seventeen and even twenty-three miles2 and on reaching the upper strata of the atmosphere1 it spread itself out in a vast canopy resembling the pine-tree form of ,vesuvian eruptions2 and throughout the long night of the #bgth this canopy continued to extend laterally1 and the particles of dust which it enclosed began to descend slowly through the air4 7f47 ,formation of ,waves4--,this tremendous outburst of volcanic forces1 which to a greater or less extent influenced the entire surface of the globe1 gave rise to waves which traversed both air and ocean2 and in consequence of the large number of observatories scattered all over the globe1 and the excellence and delicacy of the instruments of observation1 we are put in possession of the remarkable results which have been obtained from the collection of the observations in the hands of competent specialists4 ,the results are related in extenso in the ,report of the ,royal ,society1 illustrated by maps and diagrams1 and are worthy of careful study by those interested in terrestrial phenomena4 ,a brief summary is all that can be given here1 but it will probably suffice to bring home to the reader the magnitude and grandeur of the eruption4 ,the vibrations or waves generated in ,august1 #ahhc1 at ,krakatoa may be arranged under three heads3 7#a7 ,atmospheric ,waves2 7#b7 ,sound ,waves2 and 7#c7 ,oceanic ,waves2 which ,i will touch upon in the order here stated4 7#a7 ,atmospheric ,waves4--,these phenomena have been ably handled by ,general ,strachey1#h from a large number of observations extending all over the globe4 ,from these it has been clearly established that an atmospheric wave1 originating at ,krakatoa as a centre1 expanded outwards in a circular form and travelled onwards till it became a great circle at a distance of #ahj degrees from its point of origin1 after which it still advanced1 but now gradually contracting to a node at the antipodes of ,krakatoa2 that is to say1 at a point over the surface of ,north ,america1 situated in lat4 #f ,n4 and long4 #gb ,w4 7or thereabout74 ,having attained this position1 the wave was reflected or reproduced1 expanding outwards for #ahj degrees and travelling backwards again to ,krakatoa1 from which it again started1 and returning to its original form again overspread the globe4 ,this wonderful repetition1 due to the spherical form of the earth1 was observed no fewer than seven times1 though with such diminished force as ultimately to be outside the range of observation by the most sensitive instruments4 ,it is one of the triumphs of modern scientific appliances that the course of such a wave1 generated in a fluid surrounding a globe1 which might be demonstrated on mathematical principles1 has been actually determined by experiments carried on over so great an area4 7#b7 ,sound ,waves4--,if the sound-waves produced at the time of maximum eruption were not quite as far-reaching as those of the air1 they were certainly sufficiently surprising to be almost incredible1 were it not that they rest1 both as regards time and character1 upon incontestible authority4 ,the sound of the eruption1 resembling that of the discharge of artillery1 was heard not only over nearly all parts of ,sumatra1 ,java1 and the coast of ,borneo opposite the ,straits of ,sunda1 but at places over two thousand miles distant from the scene of the explosions4 ,detailed accounts1 collected with great care1 are given in the ,report of the ,royal ,society1 from which the following are selected as examples3-- #a4 ,at the port of ,acheen1 at the northern extremity of ,sumatra1 distant #a1jgc miles1 it was supposed that the port was being attacked1 and the troops were put under arms4 #b4 ,at ,singapore1 distant #ebb miles1 two steamers were dispatched to look out for the vessel which was supposed to be firing guns as signals of distress4 #c4 ,at ,bankok1 in ,siam1 distant #a1dac miles1 the report was heard on the #bgth2 as also at ,labuan1 in ,borneo1 distant #a1jcg miles4 #d4 ,at places in the ,philippine ,islands1 distant about #a1dej miles1 detonations were heard on the #bgth1 at the time of the eruption4 ,the above places lie northwards of ,krakatoa4 ,in the opposite direction1 we have the following examples3-- #e4 ,at ,perth1 in ,western ,australia1 distant #a1jib miles1 sounds as of guns firing at sea were heard2 and at the ,victorian ,plains1 distant about #a1gjj miles1 similar sounds were heard4 #f4 ,in ,south ,australia1 at ,alice's ,springs1 ,undoolga1 and other places at distances of over #b1jjj miles1 the sounds of the eruption were also heard4 #g4 ,in a westerly direction at ,dutch ,bay1 ,ceylon1 distant #b1jeh miles1 the sounds were heard between #g a4m4 and #aj a4m4 on the morning of the #bgth of ,august4 #h4 ,lastly1 at the ,chagos ,islands1 distant #b1bfg miles1 the detonations were audible between #aj and #aa a4m4 of the same day4 ,some of the above distances are so great that we may fail to realise them2 but they will be more easily appreciated1 perhaps1 if we change the localities to our own side of the globe1 and take two or three cases with similar distances4 ,then1 if the eruption had taken place amongst the volcanoes of the ,canaries1 the detonations would have been heard at ,gibraltar1 at ,lisbon1 at ,portsmouth1 ,southampton1 ,cork1 and probably at ,dublin and ,liverpool2 or1 again1 supposing the eruption had taken place on the coast of ,iceland1 the report would have been heard all over the western and northern coasts of the ,british ,isles1 as well as at ,amsterdam and the ,hague4 ,the enormous distance to which the sound travelled in the case of ,krakatoa was greatly due to the fact that the explosions took place at the surface of the sea1 and the sound was carried along that surface uninterruptedly to the localities recorded2 a range of mountains intervening would have cut off the sound-wave at a comparatively short distance from its source4 7#c7 ,oceanic ,waves4--,as may be supposed1 the eruption gave rise to great agitation of the ocean waters with various degrees of vertical oscillation2 but according to the conclusions of ,captain ,wharton1 founded on numerous data1 the greatest wave seems to have originated at ,krakatoa about #aj a4m4 on the #bgth of ,august1 rising on the coasts of the ,straits of ,sunda to a height of fifty feet above the ordinary sea-level4 ,this wave appears to have been observed over at least half the globe4 ,it travelled westwards to the coast of ,hindostan and ,southern ,arabia1 ultimately reaching the coasts of ,france and ,england4 ,eastwards it struck the coast of ,australia1 ,new ,zealand1 the ,sandwich ,islands1 ,alaska1 and the western coast of ,north ,america2 so that it was only the continent of ,north and ,south ,america which formed a barrier 7and that not absolute7 to the circulation of this oceanic wave all over the globe4 ,the destruction to life and property caused by this wave along the coasts of ,sunda was very great4 ,combined with the earthquake shocks 7which1 however1 were not very severe71 the tremendous storm of wind1 the fall of ashes and cinders1 and the changes in the sea-bed1 it produced in the ,straits of ,sunda for some time after the eruption a disastrous transformation4 ,lighthouses had been swept away2 all the old familiar landmarks on the shore were obscured by a vast deposit of volcanic dust2 the sea itself was encumbered with enormous quantities of floating pumice1 in many places of such thickness that no vessel could force its way through them2 and for months after the eruption one of the principal channels was greatly obstructed by two islands which had arisen in its midst4 ,the ,sebesi channel was completely blocked by banks composed of volcanic materials1 and two portions of these banks rose above the sea as islands1 which received the name of ,steers ,island and ,calmeyer ,island2 but these1 by the action of the waves1 have since been completely swept away1 and the materials strewn over the bed of the sea4#i 7g47 ,atmospheric ,effects4--,but the face of nature1 even in her most terrific and repulsive aspect1 is seldom altogether unrelieved by some traces of beauty4 ,in contrast to the fearful and disastrous phenomena just described1 is to be placed the splendour of the heavens1 witnessed all over the central regions of the globe throughout a period of several months after the eruption of #ahhc1 which has been ably treated by the ,hon4 ,rollo ,russell and ,mr4 ,c4 ,d4 ,archibald1 in the ,royal ,society's ,report4 ,when the particles of lava and ashes mingled with vapour were projected into the air with a velocity greater than that of a ball discharged from the largest ,armstrong gun1 these materials were carried by the prevalent trade-winds in a westerly direction1 and some of them fell on the deck of ships sailing in the ,indian ,ocean as far as long4 #hj ,e41 as in the case of the ,british ,empire--on which the particles fell on the #bith of ,august1 at a distance of #a1fjj miles from ,krakatoa4 ,but far beyond this limit1 the finer particles of dust 7or rather minute crystals of felspar and other minerals71 mingled with vapour of water1 were carried by the higher currents of the air as far as the ,seychelles and ,africa1--not only the ,east coast1 but also the ,west1 as ,cape ,coast ,castle on the ,gold ,coast2 to ,paramaribo1 ,trinidad1 ,panama1 the ,sandwich ,isles1 ,ceylon and ,british ,india1 at all of which places during the month of ,september the sun assumed tints of blue or green1 as did also the moon just before and after the appearance of the stars2#aj and from the latter end of ,september and for several months1 the sky was remarkable for its magnificent coloration2 passing from crimson through purple to yellow1 and melting away in azure tints which were visible in ,europe and the ,british ,isles2 while a large corona was observed round both the sun and moon4 ,these beautiful sky effects were objects of general observation throughout the latter part of the year #ahhc and commencement of the following year4 ,the explanation of these phenomena may be briefly stated4 ,the fine particles1 consisting for the most part of translucent crystals1 or fragments of crystals1 formed a canopy high up in the atmosphere1 being gradually spread over both sides of the equator till it formed a broad belt1 through which the rays of the sun and moon were refracted4 ,towards dawn and sunset they were refracted and reflected from the facets of the crystal1 and thus underwent decomposition into the prismatic colours2 as do the rays of the sun when refracted and reflected from the particles of moisture in a rain-cloud4 ,the subject is one which cannot be fully dealt with here1 and is rather outside the scope of this work4 7h47 ,origin of the ,eruption4--,the ultimate cause of volcanic eruptions is treated in a subsequent chapter1 nor is that of ,krakatoa essentially different from others4 ,it was remarkable1 however1 both for the magnitude of the forces evoked and the stupendous scale of the resulting phenomena4 ,it is evident that water played an important part in these phenomena1 though not as the prime mover2--any more than water in the boiler of a locomotive is the prime mover in the generation of the steam4 ,without the fuel in the furnace the steam would not be produced2 and the amount of steam generated will be proportional to the quantity and heat of the fuel in the furnace and the quantity of water in the boiler4 ,in the case of ,krakatoa1 both these elements were enormous and inexhaustible4 ,the volcanic chimney 7or system of chimneys71 being situated on an island1 was readily accessible to the waters of the ocean when fissures gave them access to the interior molten matter4 ,that such fissures were opened we may well believe4 ,the earthquakes which occurred at the beginning of ,may1 and later on1 on the #bgth of that month1 may indicate movements of the crust by which water gained access4 ,it appears that in ,may the only crater in a state of activity was that of ,perboewatan2 in ,june another crater came into action1 connected with ,danan in the centre of the island1 and in ,august a third burst forth4 ,thus there was progressive activity up to the commencement of the grand eruption of the #bfth of that month4#aa ,during this last paroxysmal stage1 the centre of the island gave way and sunk down1 when the waters of the ocean gained free access1 and meeting with the columns of molten matter rising from below originated the prodigious masses of steam which rose into the air4 7i47 ,cause of the ,detonations4--,the detonations which accompanied the last great eruption are repeatedly referred to in all the accounts4 ,these may have been due1 not only to the sudden explosions of steam directly produced by the ocean water coming in contact with the molten lava1 but by dissociation of the vapour of water at the critical point of temperature into its elements of oxygen and hydrogen2 the reunion of these elements at the required temperature would also result in explosions4 ,the phenomena attending this great volcanic eruption1 so carefully tabulated and critically examined1 will henceforth be referred to as constituting an epoch in the history of volcanic action over the globe1 and be of immense value for reference and comparison4 #a ,the eruption of ,krakatoa has been the subject of an elaborate ,report published by the ,royal ,society1 and is also described in a work by ,chevalier ,r4 ,d4 ,m4 ,verbeek1 ,ingenieur en ,chef des ,mines1 and published by order of the ,governor-,general of the ,netherland ,indies 7#ahhf74 ,see also an ,article by ,sir ,r4 ,s4 ,ball in the ,contemporary ,review for ,november1 #ahhh4 #b ,verbeek1 loc4 cit41 p4 #d4 #c ,the account of this eruption is a free translation from ,verbeek4 #d ,verbeek1 loc4 cit41 p4 #afj4 #e ,judd1 ,rep4 ,r4 ,s4 #f ,a fuller account by ,prof4 ,judd will be found in the ,report of the ,royal ,society1 p4 #ad4 ,several vessels at anchor were driven ashore on the straits owing to the strong wind which arose4 #g ,judd1 ,report1 p4 #ba4 #h ,report1 ,part ii4 #i ,in this eruption1 #cf1chj human beings perished1 of whom #cg were ,europeans2 #afc villages 7kampoengs7 were entirely1 and #acb partially1 destroyed4--,verbeek1 loc4 cit41 p4 #gi4 #aj ,verbeek1 loc4 cit41 p4 #add-e4 ,the dust put a girdle round the earth in thirteen days4 #aa ,verbeek1 loc4 cit41 p4 #cj4 ,,chapter ,,ii4 ,,earthquakes4 ,connection of ,earthquakes with ,volcanic ,action4--,the connection between earthquake shocks and volcanic eruptions is now so generally recognised that it is unnecessary to insist upon it here4 ,all volcanic districts over the globe are specially liable to vibrations of the crust2 but at the same time it is to be recollected that these movements visit countries occasionally from which volcanoes1 either recent or extinct1 are absent2 in which cases we may consider earthquake shocks to be abortive attempts to originate volcanic action4 7a47 ,origin4--,from the numerous observations which have been made regarding the nature of these phenomena by ,hopkins1 ,lyell1 and others1 it seems clearly established that earthquakes have their origin in some sudden impact of gas1 steam1 or molten matter impelled by gas or steam under high pressure1 beneath the solid crust4#a ,how such impact originates we need not stop to inquire1 as the cause is closely connected with that which produces volcanic eruptions4 ,the effect1 however1 of such impact is to originate a wave of translation through the crust1 travelling outwards from the point1 or focus1 on the surface immediately over the point of impact4#b ,these waves of translation can in some cases be laid down on a map1 and are called isoseismal curves1 each curve representing approximately an equal degree of seismal intensity2 as shown on the chart of a part of ,north ,america affected by the great ,charleston earthquake4 7,fig4 #cg47 ,mr4 ,hopkins has shown that the earthquake-wave1 when it passes through rocks differing in density and elasticity1 changes in some degree not only its velocity1 but its direction2 being both refracted and reflected in a manner analogous to that of light when it passes from one medium to another of different density4#c ,when a shock traverses the crust through a thickness of several miles it will meet with various kinds of rock as well as with fissures and plications of the strata1 owing to which its course will be more or less modified4 7b47 ,formation of ,fissures4--,during earthquake movements1 fissures may be formed in the crust1 and filled with gaseous or melted matter which may not in all cases reach the surface2 and1 on the principle that volcanoes are safety-valves for regions beyond their immediate influence1 we may infer that the earthquake shock1 which generally precedes the outburst of a volcano long dormant1 finds relief by the eruption which follows2 so that whatever may be the extent of the disastrous results of such an eruption1 they would be still more disastrous if there had been no such safety-valve as that afforded by a volcanic vent4 ,thus1 probably1 owing to the extinction of volcanic activity in ,syria1 the earthquakes in that region have been peculiarly destructive4 ,for example1 on ,january #a1 #ahcg1 the town of ,safed west of the ,jordan valley was completely destroyed by an earthquake in which most of the inhabitants perished4 ,the great earthquakes of ,aleppo in the present century1 and of ,syria in the middle of the eighteenth1 were of exceptional severity4 ,in that of ,syria1 which took place in #agei1 and which was protracted during a period of three months1 an area of #aj1jjj square leagues was affected4 ,accon1 ,saphat1 ,baalbeck1 ,damascus1 ,sidon1 ,tripoli1 and other places were almost entirely levelled to the ground2 many thousands of human beings lost their lives4#d ,other examples might be cited4 7c47 ,earthquake ,waves4--,we have now to return to the phenomena connected with the transmission of earthquake-waves4 ,the velocity of transmission through the earth is very great1 and several attempts have been made to measure this velocity with accuracy4 ,the most valuable of such attempts are those connected with the ,charleston and ,riviera shocks4 ,fortunately1 owing to the perfection of modern appliances1 and the number of observers all over the globe1 these results are entitled to great confidence4 ,the phenomena connected with the ,charleston earthquake1 which took place on the #cast of ,august1 #ahhf1 are described in great detail by ,captain ,clarence ,e4 ,dutton1 of the ,u4,s4 ,ordnance ,corps4#e ,the conclusions arrived at are2--that as regards the depth of the focal point1 this is estimated at twelve miles1 with a probable error of less than two miles2 while1 as regards the rate of travel of the earthquake-wave1 the estimate is 7in one case7 about #c4bcf miles per second2 and in another about #c4bbf miles per second4 ,on the other hand1 in the case of the earthquake of the ,riviera1 which took place on the #bcrd of ,february1 #ahhg1 at #e4cj a4m4 7local time71 the vibrations of which appear to have extended across the ,atlantic1 and to have sensibly affected the seismograph in the ,government ,signal ,office at ,washington1 the rate of travel was calculated at about #ejj miles per hour1 less than one-half that determined in the case of ,charleston2 but ,captain ,dutton claims1 and probably with justice1 that the results obtained in the latter case are far more reliable than any hitherto arrived at4 7d47 ,oceanic ,waves4--,when the originating impact takes place under the bed of the ocean--either by a sudden up-thrust of the crust to the extent1 let us suppose1 of two or three feet1 or by an explosion from a submarine volcano--a double wave is formed1 one travelling through the crust1 the other through the ocean2 and as the rate of velocity of the former is greatly in excess of that of the latter1 the results on their reaching the land are often disastrous in the extreme4 ,it is the ocean-wave1 however1 which is the more important1 and calls for special consideration4 ,if the impact takes place in very deep water1 the whole mass of the water is raised in the form of a low dome1 sloping equally away in all directions2 and it commences to travel outwards as a wave with an advancing crest until it approaches the coast and enters shallow water4 ,the wave then increases in height1 and the water in front is drawn in and relatively lowered2 so that on reaching a coast with a shelving shore the form of the surface consists of a trough in front followed by an advancing crest4 ,these effects may be observed on a small scale in the case of a steamship advancing up a river1 or into a harbour with a narrow channel1 but are inappreciable in deep water1 or along a precipitous open coast4 7e47 ,the ,earthquake of ,lisbon1 #agee4--,the disastrous results of a submarine earthquake upon the coast have never been more terribly illustrated than in the case of the earthquake of ,lisbon which took place on ,november #a1 #agee4 ,the inhabitants had no warning of the coming danger1 when a sound like that of thunder was heard underground1 and immediately afterwards a violent shock threw down the greater part of their city2 this was the land-wave4 ,in the course of about six minutes1 sixty thousand persons perished4 ,the sea first retired and left the harbour dry1 so forming the trough in front of the crest2 immediately after the water rolled in with a lofty crest1 some #ej feet above the ordinary level1 flooding the harbour and portions of the city bordering the shore4 ,the mountains of ,arrabida1 ,estrella1 ,julio1 ,marvan1 and ,cintra1 were impetuously shaken1 as it were1 from their very foundations2 and according to the computation of ,humboldt1 a portion of the earth's surface four times the extent of ,europe felt the effects of this great seismic shock1 which extended to the ,alps1 the shores of the ,baltic1 the lakes of ,scotland1 the great lakes of ,north ,america1 and the ,west ,indian ,islands4 ,the velocity of the sea-wave was estimated at about #bj miles per minute4 7f47 ,earthquake of ,lima and ,callao1 #bhth ,october1 #agdf4--,of somewhat similar character was the terrible catastrophe with which the cities of ,lima and ,callao were visited in the middle of the last century1#f in which the former city1 then one of great magnificence1 was overthrown2 and ,callao was inundated by a sea-wave1 in which out of #bc ships of all sizes in the harbour the greater number foundered2 several1 including a man-of-war1 were lifted bodily and stranded1 and all the inhabitants with the exception of about two hundred were drowned4 ,a volcano in ,lucanas burst forth the same night1 and such quantities of water descended from the cone that the whole country was overflowed2 and in the mountain near ,pataz1 called ,conversiones de ,caxamarquilla1 three other volcanoes burst forth1 and torrents of water swept down their sides4 ,in the case of these cities1 the land-wave1 or shock1 preceded the sea-wave1 which of course only reached the port of ,callao4 ,illustration3 ,fig4 #cg4--,the lines represent isoseismal curves1 or curves of equal intensity1 the force decreasing outwards from the focus at ,charleston1 ,no4 #aj4 7g47 ,earthquake of ,charleston1 #cast ,august1 #ahhf4--;,i shall close this account of some remarkable earthquakes with a few facts regarding that of ,charleston1 on the ,atlantic seaboard of ,carolina4#g ,at #i4ea a4m4 of this day1 the inhabitants engaged in their ordinary occupations were startled by the sound of a distant roar1 which speedily deepened in volume so as to resemble the noise of cannon rattling along the road1 spreading into an awful noise1 that seemed to pervade at once the troubled earth below and the still air above4 ,at the same time the floors began to heave underfoot1 the walls visibly swayed to and fro1 and the crash of falling masonry was heard on all sides1 while universal terror took possession of the populace1 who rushed into the streets1 the black portion of the community being the most demonstrative of their terror4 ,such was the commencement of the earthquake1 by which nearly all the houses of ,charleston were damaged or destroyed1 many of the public buildings seriously injured or partially demolished4 ,the effects were felt all over the ,states as far as the great lakes of ,canada and the borders of the ,rocky ,mountains4 ,two epicentral foci appear to have been established2 one lying about #ae miles to the ,n4,w4 of ,charleston1 called the ,woodstock focus2 the other about #ad miles due west of ,charleston1 called the ,rantowles focus2 around each of these foci the isoseismic curves concentrated1#h but in the map 7,fig4 #cg7 are combined into the area of one curve4 ,the position of these foci clearly shows that the origin of the ,charleston earthquake was not submarine1 though occurring within a short distance of the ,atlantic border2 the curves of equal intensity 7isoseismals7 are drawn all over the area influenced by the shock4 ,as a general result of these detailed observations1 ,captain ,dutton states that there is a remarkable coincidence in the phenomena with those indicated by the theory of wave-motion as the proper one for an elastic1 nearly homogeneous1 solid medium1 composed of such materials as we know to constitute the rocks of the outer portions of the earth2 but on the other hand he states that nothing has been disclosed which seems to bring us any nearer to the precise nature of the forces which generated the disturbance4#i #a ,the views of ,mr4 ,r4 ,mallet1 briefly stated1 are somewhat as follows3--,owing to the secular cooling of the earth1 and the consequent lateral crushing of the surface1 this crushing from time to time overcomes the resistance2 in which case shocks are experienced along the lines of fracture and faulting by which the crust is intersected4 ,these shocks give rise to earthquake waves1 and as the crushing of the walls of the fissure developes heat1 we have here the vera causa both of volcanic eruptions and earthquake shocks--the former intensified into explosions by access of water through the fissures4--,on the ,dynamics of ,earthquakes1 ,trans4 ,roy4 ,irish ,acad41 vol4 xxi4 #b ,illustration of the mode of propagation of earthquake shocks will be found in ,lyell's ,principles of ,geology1 vol4 ii4 p4 #acf1 or in the author's ,physiography1 p4 #gf1 after ,hopkins4 #c ,rep4 on ,theories of ,elevation and ,earthquakes1 ,brit4 ,ass4 ,rep4 #ahdg1 p4 #cc4 ,in the map prepared by ,prof4 ,j4 ,milne and ,mr4 ,w4 ,k4 ,burton to show the range of the great earthquake of ,japan 7#ahia71 similar isoseismal lines are laid down4 #d ,lyell1 loc4 cit41 p4 #afc4 ,two ,catalogues of ,earthquakes have been drawn up by ,prof4 ,o',reilly1 and are published in the ,trans4 ,roy4 ,irish ,academy1 vol4 xxviii4 7#ahhd and #ahhf74 #e ,ninth ,annual ,report1 ,u4,s4 ,geological ,survey 7#ahhh74 #f ,a ,true and ,particular ,account of the ,dreadful ,earthquake1 #bnd edit4 ,the original published at ,lima by command of the ,viceroy4 ,london1 #agdh4 ,translated from the ,spanish4 #g ,i take the account from that of ,capt4 ,dutton above cited1 p4 #bbj4 #h ,dutton1 ,report1 ,plate xxvi41 p4 #cjh4 #i ,ibid41 p4 #baa4 ,on the connection between the moon's position and earthquake shocks1 see ,mr4 ,richardson's paper on ,scottish earthquakes1 ,trans4 ,edin4 ,geol4 ,soc41 vol4 vi4 p4 #aid 7#ahib74 ,,part ,,vii4 ,,volcanic ,,and ,,seismic ,,problems4 ,,chapter ,i4 ,,the ,,ultimate ,,cause ,,of ,,volcanic ,,action4 ,volcanic phenomena are the outward manifestations of forces deep-seated beneath the crust of the globe2 and in seeking for the causes of such phenomena we must be guided by observation of their nature and mode of action4 ,the universality of these phenomena all over the surface of our globe1 in past or present times1 indicates the existence of a general cause beneath the crust4 ,it is true that there are to be found large tracts from which volcanic rocks 7except those of great geological antiquity7 are absent1 such as ,central ,russia1 the ,nubian ,desert1 and the ,central ,states of ,north ,america2 but such absence by no means implies the non-existence of the forces which give rise to volcanic action beneath those regions1 but only that the forces have not been sufficiently powerful to overcome the resistance offered by the crust over those particular tracts4 ,on the other hand1 the similarity of volcanic lavas over wide regions is strong evidence that they are drawn from one continuous magma1 consisting of molten matter beneath the solid exterior crust4 7a47 ,lines of ,volcanic ,action4--,it has been shown in a previous page that volcanic action of recent or ,tertiary times has taken place mainly along certain lines which may be traced on the surface of a map or globe4 ,one of these lines girdles the whole globe1 while others lie in certain directions more or less coincident with lines of flexure1 plication or faulting4 ,the ,isle of ,sumatra offers a remarkable example of the coincidence of such lines with those of volcanic vents4 ,not only the great volcanic cones1 but also the smaller ones1 are disposed in chains which run parallel to the longitudinal axis of the island 7,n4,w4-,s4,e474 ,the sedimentary rocks are bent and faulted in lines parallel to the main axis1 and also to the chains of volcanic mountains1 and the observation holds good with regard to different geological periods4#a ,another remarkable case is that of the ,jordan ,valley4 ,nowhere can the existence of a great fracture and vertical displacement of the strata be more clearly determined than along this remarkable line of depression2 and it is one which is also coincident with a zone of earthquake and volcanic disturbances4 7b47 ,such ,lines generally lie along the ,borders of the ,ocean4--,but even where1 from some special cause1 actual observation on the relations of the strata are precluded1 the general configuration of the ground and the relations of the boundaries between land and sea to those of volcanic chains1 evidently point in many cases to their mutual interdependence4 ,the remarkable straightness of the coast of ,western ,america1 and of the parallel chain of the ,andes1 affords presumptive evidence that this line is coincident with a fracture or system of faults1 along which the continent has been bodily raised out of the waters of the ocean4 ,of this elevation within very recent times we have abundant evidence in the existence of raised coral-reefs and oceanic shell-beds at intervals all along the coast2 rising in ,peru to a level of no less than #c1jjj feet above the ocean1 as shown by ,alexander ,agassiz4#b ,such elevations probably occurred at a time when the volcanoes of the ,andes were much more active than at present4 ,considered as a whole1 these great volcanic mountains may be regarded as in a dormant1 or partially moribund1 condition2 and if the volcanic forces have to some extent lost their strength1 so it would appear have those of elevation4 7c47 ,areas of ,volcanic ,action in the ,british ,isles4--,in the case of the ,british ,islands it may be observed that the later ,tertiary volcanic districts lie along very ancient depressions1 which may indicate zones of weakness in the crust4 ,thus the ,antrim plateau1 as originally constituted1 lay in the lap of a range of hills formed of crystalline1 or ,lower ,silurian1 rocks2 while the volcanic isles of the ,inner ,hebrides were enclosed between the solid range of the ,archan rocks of the ,outer ,hebrides on the one side1 and the ,silurian and ,archan ranges of the mainland on the other4 ,and if we go back to the ,carboniferous period1 we find that the volcanic district of the centre of ,scotland was bounded by ranges of solid strata both to the north and south1 where the resistance to interior pressure from molten matter would have been greater than in the ,carboniferous hollow-ground1 where such molten matter has been abundantly extruded4 ,in all these cases1 the outflow of molten matter was in a direction somewhat parallel to the plications of the strata4 7d47 ,special ,conditions under which the ,volcanic ,action operates4--,assuming1 then1 that the molten matter1 forming an interior magma or shell1 is constantly exerting pressure against the inner surface of the solid crust1 and can only escape where the crust is too weak 7owing to faults1 plications1 or fissures7 to resist the pressure1 we have to inquire what are the special conditions under which outbursts of volcanic matter take place1 and what are the general results as regards the nature of the ejecta dependent on those conditions4 7e47 ,effect of the ,presence or ,absence of ,water4--,the two chief conditions determining the nature of volcanic products1 considered in the mass1 are the presence or absence of water4 ,such presence or absence does not of course affect the essential chemical composition of the ejecta1 but it materially influences the form in which the matter is erupted4 ,the agency of water in volcanic eruptions is a very interesting and important subject in connection with the history of volcanic action1 and has been ably treated by ,professor ,prestwich4#c ,at one time it was considered that water was essential to volcanic activity2 and the fact that the great majority of volcanic cones are situated in the vicinity of the oceanic waters1 or of inland seas1 was pointed to in confirmation of this theory4 ,but the existence in ,western ,america and other volcanic countries of fissures of eruption along which molten lava has been extruded without explosions of steam1 shows that water is not an essential factor in the production of volcanic phenomena2 and1 as ,professor ,prestwich has clearly demonstrated1 it is to be regarded as an element in volcanic explosions1 rather than as a prime cause of volcanic action4 ,the main difficulty he shows to be thermo-dynamical2 and calculating the rate of increase in the elastic force of steam on descending to greater and greater depths and reaching strata of higher and higher temperatures1 as compared with the force of capillarity1 he comes to the conclusion that water cannot penetrate to depths of more than seven or eight miles1 and therefore cannot reach the seat of the eruptive forces4 ,professor ,prestwich also points out that if the extrusion of lava were due to the elastic force of vapour of water there should be a distinct relation between the discharge of the lava and of the vapour2 whereas the result of an examination of a number of well-recorded eruptions shows that the two operations are not related1 and are1 in fact1 perfectly independent4 ,sometimes there has been a large discharge of lava1 and little or no escape of steam2 at other times there have been paroxysmal explosive eruptions with little discharge of lava4 ,even in the case of ,vesuvius1 which is close to the sea1 there have been instances when the lava has welled out almost with the tranquillity of a water-spring4 7f47 ,access of ,surface ,water to ,molten ,lava during ,eruptions4--,the existence of water during certain stages in eruptions is too frequent a phenomena to be lost sight of2 but its presence may be accounted for in other ways1 besides proximity to the sea or ocean4 ,certain volcanic mountains1 such as ,etna and ,vesuvius1 are built upon water-bearing strata1 receiving their supplies from the rainfall of the surrounding country1 or perhaps partly from the sea4 ,in addition to this the ashes and scori of the mountain sides are highly porous1 and rain or snow can penetrate and settle downwards around the pipe or throat through which molten lava wells up from beneath4 ,in such cases it is easy to understand how1 at the commencement of a period of activity1 molten lava ascending through one or more fissures1 and meeting with water-charged strata or scori1 will convert the water into steam at high pressure1 resulting in explosions more or less violent and prolonged1 in proportion to the quantity of water and the depth to which it has penetrated4 ,in this manner we may suppose that ashes1 scori1 and blocks of rock torn from the sides of the crater-throat1 and hurled into the air1 are piled around the vent1 and accumulate into hills or mountains of conical form4 ,after the explosion has exhausted itself1 the molten lava quietly wells up and fills the crater1 as in the cases of those of ,auvergne and ,syria1 and other places4 ,we may1 therefore1 adopt the general principle that in volcanic eruptions where water in large quantities is present1 we shall have crater-cones built up of ashes1 scori1 and pumice2 but where absent1 the lava will be extravasated in sheets to greater or less distances without the formation of such cones2 or if cones are fanned1 they will be composed of solidified lava only1 easily distinguishable from crater-cones of the first class4 7g47 ,nature of the ,interior ,reservoir from which ,lavas are derived4--,we have now to consider the nature of the interior reservoir from which lavas are derived1 and the physical conditions necessary for their eruption at the surface4 ,without going back to the question of the original condition of our globe1 we may safely hold the view that at a very early period of geological history it consisted of a solidified crust at a high temperature1 enfolding a globe of molten matter at a still higher temperature4 ,as time went on1 and the heat radiated into space from the surface of the globe1 while at the same time slowly ascending from the interior by conduction1 the crust necessarily contracted1 and pressing more and more on the interior molten magma1 this latter was forced from time to time to break through the contracting crust along zones of weakness or fissures4 7h47 ,the ,earth's ,crust in a ,state of both ,exterior ,thrust and of ,interior ,tension4--,as has been shown by ,hopkins1#d and more recently by ,mr4 ,davison1#e an exterior crust in such a condition must eventually result in being under a state of horizontal thrust towards the exterior and of tension towards the interior surface4 ,for the exterior portion1 having cooled down1 and consequently contracted to its normal state1 will remain rigid up to a certain point of resistance2 but the interior portion still continuing to contract1 owing to the conduction of the heat towards the exterior1 would tend to enter upon a condition of tension1 as becoming too small for the interior molten magma2 and such a state of tension would tend to produce rupture of the interior part4 ,in this manner fissures would be formed into which the molten matter would enter2 and if the fissures happened to extend to the surface1 owing to weakness of the crust or flexuring of the strata1 or other cause1 the molten matter would be extruded either in the form of dykes or volcanic vents4 ,in this way we may account for the numerous dykes of trap by which some volcanic districts are intersected1 such as those of the north of ,ireland and centre of ,scotland4 ,from the above considerations1 it follows that the earth's crust must be in a condition both of pressure 7or lateral thrust7 towards the exterior portion1 and of tension towards the interior1 the former condition resulting in faulting and flexuring of the rocks1 the latter in the formation of open fissures1 through which lava can ascend under high pressure4 ,these operations are of course the attempt of the natural forces to arrive at a condition of equilibrium1 which is never attained because the processes are never completed2 in other words1 radiation and convection of heat are constantly proceeding1 giving rise to new forces of thrust and tension4 ,it now remains for us to consider what may be the condition of the interior molten magma2 and in doing so we must be guided to a large extent by considerations regarding the nature of the extruded matter at the surface4 7i47 ,relative ,densities of ,lavas4--,now1 observation shows that1 as bearing on the subject under consideration1 lavas occur mainly under two classes as regards their density4 ,the most dense 7or basic7 are those in which silica is deficient1 but iron is abundant2 the least dense 7or acid7 are those which are rich in silica1 but in which iron occurs in small quantity4 ,this division corresponds with that proposed by ,bunsen and ,durocher#f for volcanic rocks1 upon the results of analyses of a large number of specimens from various districts4 ,rocks may be thus arranged in groups3 7#a7 ,the ,basic 7,heavier7--poor in silica1 rich in iron2 containing silica #de-eh per cent4 ,examples3 ,basalt1 ,dolerite1 ,hornblende rock1 ,diorite1 ,diabase1 ,gabbro1 ,melaphyre1 and ,leucite lava4 7#b7 ,the ,acid 7,lighter7--rich in silica1 poor in iron2 containing silica #fb-gh per cent4 ,examples3 ,trachyte1 ,rhyolite1 ,obsidian1 ,domite1 ,felsite1 ,quartz-porphyry1 ,granite4 ,the ,andesite group forms a connecting link between the highly acid and the basic groups1 and there are many varieties of the above which it is not necessary to enumerate4 ,durocher supposes that the molten magmas of these various rocks are arranged in concentric shells within the solid crust in order of their respective densities1 those of the lighter density1 namely the acid magmas1 being outside those of greater density1 namely the basic2 and this is a view which seems not improbable from a consideration not only of the principle itself1 but of the succession of the varieties of lava in many districts4 ,thus we find that acid lavas have been generally extruded first1 and basic afterwards--as in the cases of ,western ,america1 of ,antrim1 the ,rhine and ,central ,france4 ,and if the interior of our globe had been in a condition of equilibrium from the time of the consolidation of the crust to the present1 reason would induce us to conclude that the lavas would ultimately have arranged themselves in accordance with the conditions of density beneath that crust4 ,but the state of equilibrium has been constantly disturbed4 ,every fresh outburst of volcanic force1 and every fresh extrusion of lava1 tends to disturb it1 and to alter the relations of the interior viscous or molten magmas4 ,owing to this it happens1 as we may suppose1 that the order of eruption according to density is sometimes broken1 and we find such rocks as granophyre 7a variety of andesite7 breaking through the plateau-basalts of ,mull and ,skye1 as explained in a former chapter4 ,notwithstanding such variations1 however1 the view of ,durocher may be considered as the most reasonable we can arrive at on a subject which is confessedly highly conjectural4 7j47 ,conclusion as regards the ,ultimate ,cause of ,volcanic ,action4--,notwithstanding1 however1 the complexity of the subject1 and the uncertainties which must attend an inquiry where some of the data are outside the range of our observation1 sufficient evidence can be adduced to enable us to arrive at a tolerably clear view of the ultimate cause of volcanic action4 ,so tempting a subject was sure to evoke numerous essays1 some of great ingenuity1 such as that of ,mr4 ,mallet2 others of great complexity1 such as that of ,dr4 ,daubeny4 ,but more recent consideration and wider observation have tended to lead us to the conclusion that the ultimate cause is the most simple1 the most powerful1 and the most general which can be suggested2 namely1 the contraction of the crust due to secular cooling of the more deeply seated parts by conduction and radiation of heat into space4 ,owing to this cause1 the enclosed molten matter is more or less abundantly extruded from time to time along the lines and vents of eruption1 so as to accommodate itself to the ever-contracting crust4 ,nor can we doubt that this process has been going on from the very earliest period of the earth's history1 and formerly at a greater rate than at present4 ,when the crust was more highly heated1 the radiation and conduction must have been proportionately more rapid4 ,owing to this cause also the contraction of the crust was accelerated4 ,to such irresistible force we owe the wonderful flexuring1 folding1 and horizontal overthrusting which the rocks have undergone in some portions of the globe--such as in the ,alps1 the ,highlands of ,scotland and of ,ireland1 and the ,alleghannies of ,america4 ,it is easy to show that the acceleration of the earth's rotation must be a consequence of such contraction2 but1 after all1 this is but one of those compensatory forces of which we see several examples in the world around us4 ,it can also be confidently inferred that at an early period of the earth's history1 when the moon was nearer to our planet than at present1 the tides were far more powerful1 and their effect in retarding the earth's rotation was consequently greater4 ,during this period the acceleration due to contraction was also greater2 and the two forces probably very nearly balanced each other4 ,both these forces 7those of acceleration and retardation7 have been growing weaker down to the present day1 though there appears to have been a slight advantage on the side of the retarding force4#g #a ,r4 ,d4 ,m4 ,verbeek1 ,krakatau1 p4 #aje 7#ahhf72 also1 ,j4 ,milne1 ,the ,great ,earthquake of ,japan1 #ahia4 #b ,bull4 ,mus4 ,comp4 ,zool41 vol4 iii4 #c ,proc4 ,roy4 ,soc41 ,no4 #bcg 7#ahhe72 also1 ,rep4 ,brit4 ,assoc4 7#ahha74 #d ,hopkins1 supra cit41 p4 #bah4 #e ,c4 ,davison and ,g4 ,h4 ,darwin1 ,phil4 ,trans41 vol4 #agh1 p2 #bda4 #f ,durocher1 ,ann4 des ,mines1 vol4 ii4 7#aheg74 #g ,see on this subject the author's ,textbook of ,physiography 7,deacon and ,co41 #ahhh71 pp4 #ef and #abb4 ,,chapter ,,ii4 ,,lunar ,,volcanoes4 ,the surface of the moon presented to our view affords such remarkable indications of volcanic phenomena of a special kind1 that we are justified in devoting a chapter to their consideration4 ,it is very tantalising that our beautiful satellite only permits us to look at and admire one half of her sphere2 but it is not a very far-fetched inference if we feel satisfied that the other half bears a general resemblance to that which is presented to the earth4 ,it is scarcely necessary to inform the reader why it is that we never see but one face2 still1 for the sake of those who have not thought out the subject ,i may state that it is because the moon rotates on her axis exactly in the time that she performs a revolution round the earth4 ,if this should not be sufficiently clear1 let the reader perform a very simple experiment for himself1 which will probably bring conviction to his mind that the explanation here given is correct4 ,let him place an orange in the centre of a round table1 and then let him move round the table from a starting-point sideways1 ever keeping his face directed towards the orange2 and when he has reached his starting-point1 he will find that he has rotated once round while he has performed one revolution round the table4 ,in this case the performer represents the moon and the orange the earth4 ,now this connection between the earth and her satellite is sufficiently close to be used as an argument 7if not as actual demonstration7 that the earth and the moon were originally portions of the same mass1 and that during some very early stage in the development of the solar system these bodies parted company1 to assume for ever after the relations of planet and satellite4 ,at the epoch referred to1 we may also suppose that these two masses of matter were in a highly incandescent1 if not even gaseous1 state2 and we conclude1 therefore1 that having been once portions of the same mass1 they are composed of similar materials4 ,this conclusion is of great importance in enabling us to reason from analogy regarding the origin of the physical features on the moon's surface1 and for the purpose of comparison with those which we find on the surface of our globe2 because it is evident that1 if the composition of the moon were essentially different from that of our earth1 we should have no basis whatever for a comparison of their physical features4 ,when the moon started on her career of revolution round the earth1 we may well suppose that her orbit was much smaller than at present4 ,she was influenced by counteracting forces1 those of gravitation drawing her towards the centre of gravity of the earth1#a and the centrifugal force1 which in the first instance was the stronger1 so that her orbit for a lengthened period gradually increased until the two forces1 those of attraction and repulsion1 came into a condition of equilibrium1 and she now performs her revolution round the earth at a mean distance of #bdj1jjj miles1 in an orbit which is only very slightly elliptical4#b ,how the period of the moon's rotation is regulated by the earth's attraction on her molten lava-sheets1 first at the surface1 and now probably below the outer crust1 has been graphically shown by ,sir ,robert ,ball1#c but it cannot be doubted that once the moon was appreciably nearer to our globe than at present4 ,the attraction of her mass produced tides in the ocean of correspondingly greater magnitude1 and capable of effecting results1 both in eroding the surface and in transporting masses of rock1 far beyond the bounds of our every-day experience4 ,of all the heavenly bodies1 the sun excepted1 the moon is the most impressive and beautiful4 ,as we catch her form1 rising as a fair crescent in the western sky after sunset1 gradually increasing in size and brilliancy night after night till from her circular disk she throws a full flood of light on our world and then passes through her decreasing phases1 we recognise her as the ,governor of the night1 or in the words of our own poet1 when in her crescent phase1 the ,diadem of night4 ,seen through a good binocular glass1 her form gains in rotundity2 but under an ordinary telescope with a four-inch objective1 she appears like a globe of molten gold4 ,yet all this light is derivative1 and is only a small portion of that she receives from the sun4 ,that her surface is a mass of rigid matter destitute of any inherent brilliancy1 appears plain enough when we view a portion of her disk through a very large telescope4 ,it was the good fortune of the author to have an opportunity for such a view through one of the largest telescopes in the world4 ,the #bg-;inch refractor manufactured by ,sir ,howard ,grubb of ,dublin1 for the ,vienna observatory1 a few years ago1 was turned on a portion of the moon's disk before being finally sent off to its destination2 and seen by the aid of such enormous magnifying power1 nothing could be more disappointing as regards the appearance of our satellite4 ,the sheen and lustre of the surface was now observed no longer2 the mountains and valleys1 the circular ridges and hollows were1 indeed1 wonderfully defined and magnified1 but the matter of which they seemed to be constituted resembled nothing so much as the pale plaster of a model4 ,one could thus fully realise the fact that the moon's light is only derivative4 ,still we must recollect that the most powerful telescope can only bring the surface of the moon to a distance from us of about #bej miles2 and it need not be said that objects seen at such a distance on our earth present very deceptive appearances2 so that we gain little information regarding the composition of the moon's crust1 or exterior surface1 simply from observation by the aid of large telescopes4 ,reasoning from analogy with our globe1 we may infer that the exterior shell of the moon consists of crystalline volcanic matter of the highly silicated1 or acid1 varieties resting upon another of a denser description1 rich in iron1 and resembling basalt4 ,this hypothesis is hazarded on the supposition that the composition of the matter of the moon's mass resembles in the main that of our globe4 ,during the process of cooling from a molten condition1 the heavier lavas would tend to fall inwards1 and allow the lighter to come to the surface1 and form the outer shell in both cases4 ,thus1 the outer crust would resemble the trachytic lavas of our globe1 and their pale colour would enable the sun's rays to be reflected to a greater extent than if the material were of the blackness of basalt4#d ,so much for the material4 ,we have now to consider the structure of the moon's surface1 and here we find ourselves treading on less speculative and safer ground4 ,all astronomers since the time of ,schroter seem to be of accord in the opinion that the remarkable features of the moon's surface are in some measure of volcanic origin1 and we shall presently proceed to consider the character of these forms more in detail4 ,but first1 and as leading up to the discussion of these physical features1 we must notice one essential difference between the constitution of the moon and of the earth2 namely1 the absence of water and of an atmosphere in the case of the moon4 ,the sudden and complete occultation of the stars when the moon's disk passes between them and the place of the observer on the earth's surface1 is sufficient evidence of the absence of air2 and1 as no cloud has ever been noticed to veil even for a moment any part of our satellite's face1 we are pretty safe in concluding that there is no water2 or at least1 if there be any1 that it is inappreciable in quantity4#e ,hence we infer that there is no animal or vegetable life on the moon's surface2 neither are there oceans1 lakes or rivers1 snowfields or glaciers1 river-valleys or caons1 islands1 stratified rocks1 nor volcanoes of the kind most prevalent on our own globe4 ,illustration3 ,fig4 #ch4--,photograph of the moon's surface 7in part7 showing the illuminated spots1 and ridges1 and the deep hollows4 ,the position of ,tycho is shown near the upper edge1 and some of the volcanic craters are very clearly seen near the margin4 ,now on looking at a photographic picture of the moon's surface 7,fig4 #ch71 we observe that there are enormous dark spaces1 irregular in outline1 but more or less approaching the circular form1 surrounded by steep and precipitous declivities1 but with sides sloping outwards4 ,these were supposed at one time to be seas2 and they retain the name1 though it is universally admitted that they contain no water4 ,some of these hollows are four ,english miles in depth4 ,the largest of these1 situated near the north pole of the moon1 is called ,mare ,imbrium2 next to it is ,mare ,serenitatis2 next1 ,mare ,tranquilitatis1 with several others4#f ,mare ,imbrium is of great depth1 and from its floor rise several conical mountains with circular craters1 the largest of which1 ,archimedes1 is fifty miles in diameter2 its vast smooth interior being divided into seven distinct zones running east and west4 ,there is no central mountain or other obvious internal sign of former volcanic activity1 but its irregular wall rises into abrupt towers1 and is marked outside by decided terraces4#g ,the ,mare ,imbrium is bounded along the east by a range of mountains called the ,apennines1 and towards the north by another range called the ,alps2 while a third range1 that of the ,caucasus1 strikes northward from the junction of the two former ranges4 ,several circular or oval craters are situated on1 and near to1 the crest of these ridges4 ,illustration3 ,fig4 #ci4--;,a magnified portion of the moon's surface1 showing the forms of the great craters with their outer ramparts4 ,the white spot with shadow is a cone rising from the centre of one of the larger craters to a great height and thus becoming illuminated by the sun's light4 ,but the greater part of the moon's hemisphere is dotted over by almost innumerable circular crater-like hollows2 sometimes conspicuously surmounting lofty conical mountains1 at other times only sinking below the general outer surface of the lunar sphere4 ,on approaching the margin1 these circular hollows appear oval in shape owing to their position on the sphere2 and the general aspect of those that are visible leads to the conclusion that there are large numbers of smaller craters too small to be seen by the most powerful telescopes4 ,these cones and craters are the most characteristic objects on the whole of the visible surface1 and when highly magnified present very rugged outlines1 suggestive of slag1 or lava1 which has consolidated on cooling1 as in the case of most solidified lava-streams on our earth4#h ,one of the most remarkable of these crateriform mountains is that named ,copernicus1 situated in a line with the southern prolongation of the ,apennines4 ,of this mountain ,sir ,r4 ,ball says3 ,it is particularly well known through ,sir ,john ,herschel's drawing1 so beautifully reproduced in the many editions of the ,outlines of ,astronomy4 ,the region to the west is dotted over with innumerable minute craterlets4 ,it has a central1 many-peaked mountain about #b1djj feet in height4 ,there is good reason to believe that the terracing shown in its interior is mainly due to the repeated alternate rise1 partial congealation and retreat of a vast sea of lava4 ,at full moon it is surrounded by radiating streaks4#i ,the view regarding the structure of ,copernicus here expressed is of importance1 as it is probably applicable to all the craters of our satellite4 ,when the moon is five or six days old1 says ,sir ,robert ,ball1 a beautiful group of three craters will be readily found on the boundary line between night and day4 ,these are ,catharina1 ,cyrillus1 and ,theophilus4 ,catharina is the most southerly of the group1 and is more than #af1jjj feet deep and connected to ,cyrillus by a wide valley2 but between ,cyrillus and ,theophilus there is no such connection4 ,indeed ,cyrillus looks as if its huge surrounding ramparts1 as high as ,mont ,blanc1 had been completely finished when the volcanic forces commenced the formation of ,theophilus1 the rampart of which encroaches considerably on its older neighbour4 ,theophilus stands as a well-defined round crater1 about #fd miles in diameter1 with an internal depth of #ad1jjj to #ah1jjj feet1 and a beautiful central group of mountains1 one-third of that height1 on its floor4 ,this proves that the last eruptive efforts in this part of the moon fully equalled in intensity those that had preceded them4 ,although ,theophilus is on the whole the deepest crater we can see in the moon1 it has received little or no deformation by secondary eruptions4 ,but perhaps the most remarkable object on the whole hemisphere of the moon is the majestic ,tycho1 which rises from the surface near the south pole1 and at a distance of about #a_/fth of the diameter of the sphere from its margin4 ,its depth is stated by ,ball to be #ag1jjj feet1 and its diameter #ej miles4 ,but its special distinction amongst the other volcanic craters lies in the streaks of light which radiate from it in all directions for hundreds and even thousands of miles1 stretching with superb indifference across vast plains1 into the deepest craters1 and over the highest opposing ridges4 ,when the sun rises on ,tycho these streaks are invisible1 but as soon as it has reached a height of #be to #cj above the horizon1 the rays emerge from their obscurity1 and gradually increase in brightness until full moon1 when they become the most conspicuous objects on her surface4 ,as yet no satisfactory explanation has been given of the origin of these illuminated rays1#aj but ,i may be permitted to add that their form and mode of occurrence are eminently suggestive of gaseous exhalations from the volcano illumined by the sun's rays2 and owing to the absence of an atmosphere1 spreading themselves out in all directions and becoming more and more attenuated until they cease to be visible4 ,the above account will probably suffice to give the reader a general idea of the features and inferential structure of the moon's surface4 ,that she was once a molten mass is inferred from her globular form2 but1 according to ,g4 ,f4 ,chambers1 the most delicate measurements indicate no compression at the poles4#aa ,that her surface has cooled and become rigid is also a necessary inference2 though ,sir ,j4 ,herschel considered that the surface still retains a temperature possibly exceeding that of boiling water4#ab ,however this may be1 it is pretty certain that whatever changes may occur upon her surface are not due to present volcanic action1 all evidence of such action being admittedly absent4 ,if1 when the earth and moon parted company1 their respective temperatures were equal1 the moon being so much the smaller of the two would have cooled more rapidly1 and the surface may have been covered by a rigid crust when as yet that of the earth may have been molten from heat4 ,hence the rigidity of the moon's surface may date back to an immensely distant period1 but she may still retain a high temperature within this crust4 ,having arrived at this stage of our narrative1 we are in a position to consider by what means1 and under what conditions1 the cones and craters which diversify the lunar surface have been developed4 ,in doing so it may be desirable1 in the first place1 to determine what form of crater on our earth's surface those of the moon do not represent2 and we are guided in our inquiry by the consideration of the absence of water on the lunar surface4 ,now there are large numbers of crateriform mountains on our globe in the formation of which water has played an important1 indeed essential1 part4 ,as we have already seen1 water1 though not the ultimate cause of volcanic eruptions1 has been the chief agent1 when in the form of steam at high pressure1 in producing the explosions which accompany these eruptions1 and in tearing up and hurling into the air the masses of rock1 scori1 and ashes1 which are piled around the vents of eruption in the form of craters during periods of activity4 ,to this class of craters those of ,etna1 ,vesuvius1 and ,auvergne belong4 ,these mountains and conical hills 7the domes excepted7 are all built up of accumulations of fragmental material1 with occasional sheets and dykes of lava intervening2 and where eruptions have taken place in recent times1 observation has shown that they are accompanied by outbursts of vast quantities of aqueous vapour1 which has been the chief agent 7along with various gases7 in piling up the circular walls of the crater4 ,it has also been shown that in many instances these crater-walls have been breached on one side1 and that streams of molten lava which once occupied the cup to a greater or less height1 have poured down the mountain side4 ,hence the form or outline of many of these fragmental craters is crescent-shaped4 ,such breached craters are to be found in all parts of the world1 and are not confined to any one district1 or even continent1 so that they may be considered as characteristic of the class of volcanic crater-cones to which ,i am now referring4 ,in the case of the moon1 however1 we fail to observe any decided instances of breached craters1 with lava-streams1 such as those ,i have described4#ac ,in nearly all cases the ramparts appear to extend continuously round the enclosed depression1 solid and unbroken2 or at least with no large gap occupying a very considerable section of the circumference4 7,see ,fig4 #ch47 ,hence we are led to suspect that there is some essential distinction between the craters on the surface of the moon and the greater number of those on the surface of our earth4 ,it is scarcely necessary to add that the volcanic mountains of the moon offer no resemblance whatever to the dome-shaped volcanic mountains of our globe4 ,if it were otherwise1 the lunar mountains would appear as simple luminous points rising from a dark floor1 over which they would cast a conical shadow4 ,but the form of the lunar volcanic mountains is essentially different2 as already observed1 they consist in general of a circular rampart enclosing a depressed floor1 sometimes terraced as in the case of ,copernicus1 from which rise one or more conical mountains1 which are in effect the later vents of eruption4 ,in our search1 therefore1 for analogous forms on our own earth1 we must leave out the craters and domes of the type furnished by the ,european volcanoes and their representatives abroad1 and have recourse to others of a different type4 ,is there then1 we may ask1 any type of volcanic mountain on our globe comparable with those on the moon8 ,in all probability there is4 ,if the reader will turn to the description of the volcanoes of the ,hawaiian group in the ,pacific1 especially that of ,mauna ,loa1 as given by ,professor ,dana and others1 and compare it with that of ,copernicus1 he will find that in both cases we have a circular rampart of solid lava enclosing a vast plain of the same material from which rise one or more lava-cones4 ,the interiors in both cases are terraced4 ,so that1 allowing for differences in magnitude1 it would seem that there is no essential distinction between lunar craters and terrestrial craters of the type of ,mauna ,loa4 ,dana calls these ,hawaiian volcanoes basaltic1 basalt being the prevalent material of which they are formed4 ,those of the moon may be composed of similar material1 or otherwise2 but in either case we may suppose they are built up of lava1 erupted from vents connected with the molten reservoirs of the interior4 ,thus we conclude that they belong to an entirely different type1 and have been built up in a different manner1 from those represented by ,etna1 ,vesuvius1 and most of the extinct volcanoes of ,auvergne1 the ,eifel1 and of other districts considered in these pages4 ,let us now endeavour to picture to ourselves the stages through which the moon may be supposed to have passed from the time her surface began to consolidate owing to the radiation of her heat into space2 for there is every probability that some of the craters now visible on her disk were formed at a very early period of her physical history4 ,when the surface began to consolidate1 it must also have contracted2 and the interior molten matter1 pressed out by the contracting crust1 must have been over and over again extruded through fissures produced over the solidified surface1 until the solid crust extended over the whole lunar surface1 and became of considerable thickness4 ,it is from this epoch that1 in all probability1 we should date the commencement of what may be termed the volcanic history of the moon4 ,we must bear in mind that although the moon's surface had become solid1 its temperature may have remained high for a very long period4 ,but the continuous radiation of the surface-heat into space would produce continuous contraction1 while the convection of the interior heat would tend to increase the thickness of the outer solid shell2 and this1 ever pressing with increasing force on the interior molten mass1 would result in frequent ruptures of the shell1 and the extrusion of molten lava rising from below4 ,hence we may suppose the fissure-eruptions of lava were of frequent occurrence for a lengthened period during the early stage of consolidation of the lunar crust2 but afterwards these may be supposed to have given place to eruptions through pipes or vents1 resulting in the formation of the circular craters which form such striking and characteristic objects in the physical aspect of our satellite4#ad ,it is not to be supposed that the various physical features on the lunar surface have all originated in the same way4 ,the great ranges of mountains previously described may have originated by a process of piling up of immense masses of molten lava extruded from the interior through vents or fissures2 while the great hollows 7or seas7 are probably due to the falling inwards of large spaces owing to the escape of the interior lava4 ,but it is with the circular craters that we are most concerned4 ,judging from analogy with the lava-craters present on our globe1 we must suppose them to be due to the extrusion1 and piling up1 of lava through central pipes1 followed in some cases by the subsidence of the floor of the crater4 ,it seems not improbable that it was in this way the greater number of the circular craters lying around ,tycho1 and dotting so large a space round the margin of the moon1 were constructed4 7,see ,fig4 #ch47 ,in general they appear to consist of an elevated rim1 enclosing a depressed plain1 out of which a central cone arises4 ,the rim may be supposed to have been piled up by successive discharges of lava from a central orifice2 and after the subsidence of the paroxysm the lava still in a molten condition may have sunk down1 forming a seething lake within the vast circular rampart1 as in the case of the ,hawaiian volcanoes4 ,the terraces observable within the craters in some instances have probably been left by subsequent eruptions which have not attained to the level of preceding ones2 and where a central crater-cone is seen to rise within the caldron1 we may suppose this to have been built up by a later series of eruptions of lava through the original pipe after the consolidation of the interior sea of lava4 ,the mamelons of the ,isle of ,bourbon1#ae and some of the lava-cones of ,hawaii1 appear to offer examples on our earth's surface of these peculiar forms4 ,such are the views of the origin of the physical features of our satellite which their form and inferred constitution appear to suggest4 ,they are not offered with any intention of dogmatising on a subject which is admittedly obscure1 and regarding which we have by no means all the necessary data for coming to a clear conclusion4 ,all that can be affirmed is1 that there is a great deal to be said in support of them1 and that they are to some extent in harmony with phenomena within range of observation on the surface of our earth4 ,the far greater effects of lunar vulcanicity1 as compared with those of our globe1 may be accounted for to some extent by the consideration that the force of gravity on the surface of the moon is only one-sixth of that on the surface of the earth4 ,hence the eruptive forces of the interior of our satellite have had less resistance to overcome than in the case of our planet2 and the erupted materials have been shot forth to greater distances1 and piled up in greater magnitude1 than with us4 ,we have also to recollect that the abrading action of water has been absent from the moon2 so that1 while accumulations of matter had been proceeding throughout a prolonged period over its surface1 there was no counteracting agency of denudation at work to modify or lessen the effects of the ruptive forces4 #a ,correctly speaking1 each attracts the other towards its centre of gravity with a force proportionate to its mass1 and inversely as the square of the distance2 but the earth being by much the larger body1 its attraction is far greater than that of the moon4 #b ,the variation in the distance is only under rare circumstances #dj1jjj miles1 but ordinarily about #ac1jjj miles4 #c ,story of the ,heavens1 #bnd edition1 p4 #ebe1 et seq4 #d ,a series of researches made by ,zllner1 of ,leipzig1 led him to assign to the light-reflecting capacity of the full-moon a result intermediate between that obtained by ,bouguer1 which gave a brightness equal to #a_/cjjjjj part of that of the sun1 and of ,wollaston1 which gave #a_/hjajgj part4 ,we may accept #a_/fahjjj of ,zllner as sufficiently close2 so that it would require #fjj1jjj full moons to give the same amount of light as that of the sun4 #e ,schroter1 however1 came to the conclusion that the moon has an atmosphere4 #f ,a chart of the moon's surface1 with the names of the principal physical features1 will be found in ,ball's ,story of the ,heavens1 #bnd edit41 p4 #fj4 ,it must be remembered that the moon as seen through a telescope appears in reversed position4 #g ,ibid41 p4 #ff4 #h ,as represented by ,nasmyth's models in plaster4 #i ,ball1 loc4 cit41 p4 #fg4 #aj ,ball1 loc4 cit41 p4 #fi4 #aa ,astronomy1 p4 #gh4 #ab ,outlines of ,astronomy1 p4 #bhe4 #ac ,at rare intervals a few crescent-shaped ridges are discernible on the lunar sphere1 but it is very doubtful if they are to be regarded as breached craters4 #ad ,the number of spots on the moon was considered to be #bdd until ,schroter increased it to #f1jjj1 and accurately described many of them4 ,schroter seems to have been the earliest observer who identified the circular hollows on the moon's surface as volcanic craters4 #ae ,drawings of these very curious forms are given by ,judd1 ,volcanoes1 p4 #abg4 ,,chapter ,,iii4 ,,are ,,we ,,living ,,in ,,an ,,epoch ,,of ,,special ,,volcanic ,,activity8 ,the question which we are about to discuss in the concluding chapter of this volume is one to which we ought to be able to offer a definite answer4 ,this can only be arrived at by a comparison of the violence and extent of volcanic and seismic phenomena within the period of history with those of pre-historic periods4 ,at first sight we might be disposed to give to the question an affirmative reply when we remember the eruptions of the last few years1 and add to these the volcanic outbursts and earthquake shocks which history records4 ,the cases of the earthquake and eruption in ,japan of ,november1 #ahia1 where in one province alone two thousand people lost their lives and many thousand houses were levelled#a2 that of ,krakatoa1 in #ahhc2 of ,vesuvius1 in #ahgb2 and many others of recent date which might be named1 added to those which history records2--the recollection of such cases might lead us to conclude that our epoch is one in which the subterranean volcanic forces had broken out with extraordinary energy over the earth's surface4 ,still1 when we come to examine into the cases of recorded eruptions--especially those of great violence--we find that they are limited to very special districts2 and even if we extend our retrospect into the later centuries of our era1 we shall find that the exceptionally great eruptions have been confined to certain permanently volcanic regions1 such as the chain of the ,andes1 that of the ,aleutian1 ,kurile1 ,japanese1 and ,philippine and ,sunda ,islands1 lying for the most part along the remarkable volcanic girdle of the world to which ,i have referred in a previous page4 ,add to these the cases of ,iceland and the volcanic islands of the ,pacific1 and we have almost the whole of the very active volcanoes of the world4 ,then for the purposes of our inquiry we have to ascertain how these active vents of eruption compare1 as regards the magnitude of their operations1 with those of the pre-historic and later ,tertiary times4 ,but before entering into this question it maybe observed1 in the first place1 that a large number of the vents of eruption1 even along the chain of the earth's volcanic girdle1 are dormant or extinct4 ,this observation applies to many of the great cones and domes of the ,andes1 including ,chimborazo and other colossal mountains in ,ecuador1 ,columbia1 ,chili1 ,peru1 and ,mexico4 ,the region between the eastern ,rocky ,mountains and the western coast of ,north ,america was1 as we have seen1 one over which volcanic eruptions took place on a vast scale in later ,tertiary times2 but one in which only the after-effects of volcanic action are at present in operation4 ,we have also seen that the chain of volcanoes of ,japan and of the ,kurile ,islands are only active to a slight extent as compared with former times1 and the same observation applies to those of ,new ,zealand4 ,out of #acj volcanoes in the ,japanese islands1 only #dh are now believed to be active4 ,again1 if we turn to other districts we have been considering1 we find that in the ,indian ,peninsula1 in ,arabia1 in ,syria and the ,holy ,land1 in ,persia1 in ,abyssinia and ,asia ,minor--regions where volcanic operations were exhibited on a grand scale throughout the ,tertiary period1 and in some cases almost down into recent times--we are met by similar evidences either of decaying volcanic energy1 or of an energy which1 as far as surface phenomena are concerned1 is a thing of the past4 ,lastly1 turning our attention to the ,european area1 notwithstanding the still active condition of ,etna1 ,vesuvius1 and a few adjoining islands1 we see in all directions throughout ,southern ,italy evidences of volcanic operations of a past time1--such as extinct crater-cones1 lakes occupying the craters of former volcanoes1 and extensive deposits of tuff or streams of lava--all concurring in giving evidence of a period now past1 when vulcanicity was widespread over regions where its presence is now never felt except when some earthquake shock1 like that of the ,riviera1 brings home to our minds the fact that the motive force is still beneath our feet1 though under restrained conditions as compared with a former period4 ,similar conclusions are applicable with even greater force to other parts of the ,european area4 ,the region of the ,lower ,rhine and ,moselle1 of ,hungary and the ,carpathians1 of ,central ,france1 of the ,north of ,ireland and the ,inner ,hebrides1 all afford evidence of volcanic operations at a former period on an extensive scale2 and the contrast between the present physically silent and peaceful condition of these regions1 as regards any outward manifestations of sub-terrestrial forces1 compared with those which were formerly prevalent1 cannot fail to impress our minds irresistibly with the idea that volcanic energy has well-nigh exhausted itself over these tracts of the earth's surface4 ,from this general survey of the present condition of the earth's surface1 as regards the volcanic operations going on over it1 and a comparison with those of a preceding period1 we are driven to the conclusion that1 however violent and often disastrous are the volcanic and seismic phenomena of the present day1 they are restricted to comparatively narrow limits2 and that even within these limits the volcanic forces are less powerful than they were in pre-historic times4 ,the middle part of the ,tertiary period appears1 in fact1 to have been one of extraordinary volcanic activity1 whether we regard the wide area over which this activity manifested itself1 or the results as shown by the great amount of the erupted materials4 ,many of the still active volcanic chains1 or groups1 probably had their first beginnings at the period referred to2 but in the majority of cases the eruptive forces have become dormant or extinct4 ,with the exception of the lavas of the ,indian-,peninsular area1 which appear1 at least partially1 to belong to the close of the ,cretaceous epoch1 the specially volcanic period may be considered to extend from the beginning of the ,miocene down to the close of the ,pliocene stage4 ,during the ,eocene stage1 volcanic energy appears to have been to a great degree dormant2 but plutonic energy was gathering strength for the great effort of the ,miocene epoch1 when the volcanic forces broke out with extraordinary violence over ,europe1 the ,british ,isles1 and other regions1 and continued to develop throughout the succeeding ,pliocene epoch1 until the whole globe was surrounded by a girdle of fire4 99 99 99 99 99 ,the reply1 therefore1 to the question with which we set out is very plain2 and is to the effect that the present epoch is one of comparatively low volcanic activity4 ,the further question suggests itself1 whether the volcanic phenomena of the middle ,tertiary period bear any comparison with those of past geological times4 ,this1 though a question of great interest1 is one which is far too large to be discussed here2 and it is doubtful if we have materials available upon which to base a conclusion4 ,but it may be stated with some confidence1 in general terms1 that the history of the earth appears to show that1 throughout all geological time1 our world has been the theatre of intermittent geological activity1 periods of rest succeeding those of action2 and if we are to draw a conclusion regarding the present and future1 it would be that1 owing to the lower rate of secular cooling of the crust1 volcanic action ought to become less powerful as the world grows older4 #a ,admirably illustrated in ,prof4 ,j4 ,milne's recently published work1 ,the ,great ,earthquake of ,japan1 #ahia4 ,,appendix4 ,a ,,brief ,,account ,,of ,,the ,,principal ,,varieties ,,of ,,volcanic ,,rocks4 ,the text-books on this subject are so numerous and accessible1 that a very brief account of the volcanic rocks is all that need be given here for the purposes of reference by readers not familiar with petrological details4 ,let it be observed1 in the first place1 that there is no hard and fast line between the varieties of igneous and volcanic rocks4 ,in this as in other parts of creation--natura nil facit per saltum2 there are gradations from one variety to the other4 ,at the same time a systematic arrangement is not only desirable1 but necessary2 and the most important basis of arrangement is that founded on the proportion of silica 7or quartz7 in the various rocks1 as first demonstrated by ,durocher and ,bunsen1 who showed that silica plays the same part in the inorganic kingdom that carbon does in the organic4 ,upon this hypothesis1 which is a very useful one to work with1 these authors separated all igneous and volcanic rocks into two classes1 viz41 the ,basic and the ,acid2 the former containing from #de-eh per cent41 the latter #fb-gh per cent4 of that mineral4 ,but there are a few intermediate varieties which serve to bridge over the space between the ,basic and ,acid ,groups4 ,the following is a generalised arrangement of the most important rocks under the above heads3-- ,tabular ,view of ,chief ,igneous and ,volcanic ,rocks4 ,,basic ,,group4 #a4 ,basalt and ,dolerite4 #b4 ,gabbro4 #c4 ,diorite4 #d4 ,diabase and ,melaphyre4 #e4 ,porphyrite4 ,,intermediate ,,group4 #f4 ,syenite4 #g4 ,mica-trap1 or ,lampophyre4 #h4 ,andesite4 ,,acid ,,group4 #i4 ,trachyte1 ,domite1 and ,phonolite4 #aj4 ,rhyolite and ,obsidian4 #aa4 ,granophyre4 #ab4 ,granite4 ,in the above grouping1 and in the following definitions1 ,i have not been able to follow any special authority4 ,but the most serviceable text-books are those of ,mr4 ,frank ,rutley1 ,study of ,rocks1 and ,dr4 ,hatch1 ,petrology2 also ,h4 ,rosenbusch1 ,mikroskopische ,physiographie der ,mineralien1 and ,f4 ,zirkel's ,untersuchungen ber mikroskopische ,structur der ,basaltgesteine4 ,we shall consider these in the order above indicated3-- #a4 ,,basalt4--,the most extensively distributed of all volcanic rocks4 ,it is a dense1 dark rock of high specific gravity 7#b4d-b4h71 consisting of plagioclase felspar 7,labradorite or anorthite71 augite1 and titano-ferrite 7titaniferous magnetite74 ,olivine is often present2 and when abundant the rock is called olivine-basalt4 ,in the older rocks1 basalt has often undergone decomposition into melaphyre2 and amongst the metamorphic rocks it has been changed into diorite or hornblende rock2 the augite having been converted into hornblende4 ,when leucite or nepheline replaces plagioclase1 the rock becomes a leucite-basalt1#a or nepheline-basalt4 ,some basalts have a glass paste1 or ground-mass1 in which the minerals are enclosed4 ,the lava of ,vesuvius may be regarded as a variety of basalt in which leucite replaces plagioclase1 although this latter mineral is also present4 ,zirkel calls it ,sanidin-leucitgestein1 as both the macroscopic and microscopic structure reveal the presence of leucite1 sanidine1 plagioclase1 nephiline1 augite1 mica1 olivine1 apatite1 and magnetite4#b ,dolerite does not differ essentially from basalt in composition or structure1 but is a largely crystalline-granular variety1 occurring more abundantly than basalt amongst the more ancient rocks1 and the different minerals are distinctly visible to the naked eye4 ,a remarkable variety of this rock occurs at ,slieve ,gullion in ,ireland1 in which mica is so abundant as to constitute the rock a micaceous dolerite4 #b4 ,,gabbro4--,a rather wide group of volcanic rocks with variable composition4 ,essentially it is a crystalline-granular compound of plagioclase1 generally ,labradorite and diallage4 ,sometimes the pyroxenic mineral becomes hypersthene1 giving rise to hypersthene-gabbro2 or when hornblende is present1 to hornblende-gabbro2 when olivine1 to olivine-gabbro4 ,magnetite is always present4 ,these rocks occur in the ,carlingford district in ,ireland1 in the ,lizard district of ,cornwall1 the ,inner ,hebrides 7,mull1 ,skye1 etc47 of ,scotland1 and in ,saxony4 #c4 ,,diorite4--,a crystalline-granular compound of plagioclase and hornblende with magnetite4 ,when quartz is present it becomes 7according to the usual ,british acceptation7 a syenite2 but this view is gradually giving place to the ,german definition of syenite1 which is a compound of orthoclase and hornblende2 and it may be better to denominate the variety as quartz-diorite4 ,the diorites are abundant as sheets and dykes amongst the older palozoic and metamorphic rocks1 and are sometimes exceedingly rich in magnetite4 ,mica1 epidote1 and chlorite are also present as accessories4 ,the rock occurs in ,north ,wales1 ,charnwood ,forest1 ,wicklow1 ,galway1 and ,donegal1 and the ,highlands of ,scotland4 ,there can be little doubt that amongst the metamorphic rocks of ,galway1 ,mayo1 and ,donegal the great beds of 7often columnar7 diorite were originally augitic lavas1 which have since undergone transformation4 #d4 ,,diabase4--,it is very doubtful if ,diabase ought to be regarded as a distinct species of igneous rock1 as it seems to be simply an altered variety of basalt or dolerite1 in which chlorite1 a secondary alteration-product1 has been developed by the decomposition of the pyroxene or olivine of the original rock4 ,it is a convenient name for use in the field when doubt occurs as to the real nature of an igneous rock4 ,melaphyre is a name given to the very dark varieties of altered augitic lavas1 rich in magnetite and chlorite4 #e4 ,,porphyrite 7or quartzless porphyry74--,a basic variety of felstone-porphyry1 consisting of a felspathic base with distinct crystals of felspar1 with which there may be others of hornblende1 mica1 or augite4 ,the colour is generally red or purple1 and it weathers into red clay1 in contrast to the highly acid or silicated felsites which weather into whitish sand4 #f4 ,,syenite4--,as stated above1 this name has been variously applied4 ,its derivation is from ,syene 7,assouan7 in ,egypt1 and the granitic rocks of that district were called syenites1 under the supposition 7now known to be erroneous7 that they differ from ordinary granites in that they were supposed to be composed of quartz1 felspar1 and hornblende1 instead of quartz1 felspar1 and mica4 ,from this it arose that syenite was regarded as a variety of granite in which the mica is replaced by hornblende1 and this has generally been the ,british view of the question4 ,but the ,german definition is applied to an entirely different rock1 belonging to the felstone family2 and according to this classification syenite consists of a crystalline-granular compound of orthoclase and hornblende1 in which quartz may or may not be present4 ,from this it will be seen that1 according to ,zirkel1 syenite is essentially distinct from diorite in the species of its felspar4#c ,it seems desirable to adopt the ,german view2 and as regards diorites containing quartz as an accessory1 to apply to them the name of quartz-diorite1 as stated above1 the name syenite as used by ,british geologists having arisen from a misconception4 #g4 ,,mica-,,trap 7,,lampophyre74--,a rock1 allied to the felstone family1 in which mica is an abundant and essential constituent1 thus consisting of plagioclase and mica1 with a little magnetite4 ,quartz may be an accessory4 ,this rock occurs amongst the ,lower ,silurian strata of ,ireland1 ,cumberland1 and the ,south of ,scotland2 it is not volcanic in the ordinary acceptation of that term4 ,the term lampophyre was introduced by ,gmbel in describing the mica-traps of ,fichtelgebirge4 #h4 ,,andesite4--,this is a dark-coloured1 compact or vesicular1 semi-vitreous group of volcanic rocks1 composed essentially of a glassy plagioclase felspar1 and a ferro-magnesian constituent enclosed in a glassy base4 ,according to the nature of the ferro-magnesian constituent1 the group may be divided into hornblende-andesite1 biotite-andesite1 and augite-andesite4 ,quartz is sometimes present1 and when this mineral becomes an essential it gives rise to a variety called quartz-andesite or dacite4 ,these rocks are the principal constituents of the lavas of the ,andes1 and the name was first applied to them by ,leopold von ,buch2 but their representatives also occur in the ,british ,isles1 ,germany1 and elsewhere4 ,dacite is the lava of ,krakatoa and some of the volcanoes of ,japan4 #i1 #aj4 ,,trachyte and ,,domite1 etc4--,these names include very numerous varieties of highly silicated volcanic rock1 and in their general form consist of a white felsitic paste with distinct crystals of sanidine1 together with plagioclase1 augite1 biotite1 hornblende1 and accessories4 ,when crystalline grains or blebs of quartz occur1 we have a quartz-trachyte2 when tridymite is abundant1 as in the trachyte of ,co4 ,antrim1 we have tridymite-trachyte4 ,the trachytes occupy a position between the pitchstone lavas on the one hand1 and the andesites and granophyres on the other4 7b47 ,domite is the name applied to the trachytic rocks of the ,auvergne district and the ,puy de ,dme particularly4 ,they do not contain free quartz1 though they are highly acid rocks1 containing sometimes as much as #fh per cent4 of silica4 7c47 ,phonolite 7,clinkstone7 is a trachytic rock1 composed essentially of sanidine1 nepheline1 and augite or hornblende4 ,it is usually of a greenish colour1 hard and compact1 so as to ring under the hammer2 hence the name4 ,the ,wolf ,rock is composed of phonolite1 and it occurs largely in ,auvergne4 7d47 ,rhyolites are closely connected with the quartz-trachytes1 but present a marked fluidal1 spherulitic1 or perlitic structure4 ,they consist of a trachytic ground-mass in which grains or crystals of quartz and sanidine1 with other accessory minerals1 are imbedded4 ,they occur amongst the volcanic rocks of the ,british ,isles1 ,hungary1 and the ,lipari ,islands1 from which the name ,liparite has been derived4 7e47 ,obsidian 7,pitchstone74--,this is a vitreous1 highly acid rock1 which has become a volcanic glass in consequence of rapid cooling1 distinct minerals not having had time to form4 ,it has a conchoidal fracture1 various shades of colour from grey to black2 and under the microscope is seen to contain crystallites or microliths1 often beautifully arranged in stellate or feathery groups4 ,spherulitic structure is not infrequent2 and occasionally a few crystals of sanidine1 augite1 or hornblende are to be seen imbedded in the glassy ground-mass4 ,the rock occurs in dykes and veins in the ,western ,isles of ,scotland1 in ,antrim1 and on the borders of the ,mourne ,mountains1 near ,newry1 in ,ireland4 #aa4 ,,granophyre4--,this term1 according to ,geikie1 embraces the greater portion of the acid volcanic rocks of the ,inner ,hebrides4 ,they are closely allied to the quartz-porphyries1 and vary in texture from a fine felsitic or crystalline-granular quartz-porphyry1 in the ground-mass of which porphyritic turbid felspar and quartz may generally be detected1 to a granitoid rock of medium grain1 in which the component dull felspar and clear quartz can be readily distinguished by the naked eye4 ,throughout all the varieties of texture there is a strong tendency to the development of minute irregularly-shaped cavities1 inside of which quartz or felspar has crystallised out--a feature characteristic of the granites of ,arran and of the ,mourne ,mountains4 #ab4 ,,granite4--,a true granite consists of a crystalline-granular rock consisting of quartz1 felspar 7orthoclase71 and mica2 the quartz is the paste or ground-mass in which the felspar and mica crystals are enclosed4 ,this is the essential distinction between a granite and a quartz-porphyry or a granophyre4 ,owing to the presence of highly-heated steam under pressure in the body of the mass when in a molten condition1 the quartz has been the last of the minerals to crystallise out1 and hence does not itself occur with the crystalline form4 ,true granite is not a volcanic rock1 and its representatives amongst volcanic ejecta are to be found in the granophyres1 quartz-porphyries1 felsites1 trachytes1 and rhyolites so abundant in most volcanic countries1 and to one or other of these the so-called granites of the ,mourne ,mountains1 of ,arran ,island1 and of ,skye are to be referred4 ,granite is a rock which has been intruded in a molten condition amongst the deep-seated parts of the crust1 and has consolidated under great pressure in presence of aqueous vapour and with extreme slowness1 resulting in the formation of a rock which is largely crystalline-granular4 ,its presence at the surface is due to denudation of the masses by which it was originally overspread4 ,illustration3 ,plate ,i4 ,,explanation ,,of ,,plate ,i4 ,,magnified ,,sections ,,of ,,vesuvian ,,minerals4 ,fig4 #a4 ,section of leucite crystal from the lava of #ahfh1 with fluid cavities4 ,mag41 #cej diams4 #b1 #c1 #d1 and #e4 ,sections of nepheline crystals from the lava of #agfg1 #ahcd1 and #ahed4 #f4 ,section of sodalite crystal from the lava of #agid1 with belonites and crystals of magnetite enclosed4 #g1 #h1 #i4 ,crystals of leucite with microliths and cavities darkened by magnetite dust2 also1 containing crystals of magnetite4 #aj4 ,group of leucite crystals of irregular form from the lava of #ahee1 congregated around a nucleus of crystals of plagioclase and magnetite4 ,illustration3 ,plate ,,ii4 ,,explanation ,,of ,,plate ,,ii4 ,,magnified ,,sections ,,of ,,vesuvian ,,minerals4 ,fig4 #a4 ,section of augite crystal from the lava of #agid1 with numerous gas cells and delicately banded walls4 ,the interior contains two long prisms1 probably of apatite4 #b4 ,crystal of augite with banded walls1 and indented by leucite crystals1 from the lava of #agid4 ,mag41 #dj diams4 #c1 #d1 #e4 ,sections of augite crystals from the lavas of #agid and #ahbj4 #f4 ,group of augite crystals from the lava of #ahce4 #g4 ,ditto from the lava of #ahbb1 with encluded mica-flake 7a7 and portion of the glass paste1 or ground-mass1 of the rock 7b71 containing microliths and grains of magnetite4 ,fig4 #h4 ,two crystals of olivine from the lava of #ahee2 they are intersected on one side by the plane of the thin section1 and are remarkable for showing lines of gas cells1 and bands of growth sometimes cellular4 ,mag41 #dj diams4 #i4 ,section of rock-crystal 7quartz71 with double terminal pyramids1 from the lava of #ahej4 #aj4 ,twin crystal of sanidine from the lava of #aheh4 ,mag41 #dj diams4 #aa1 #ab1 #ac4 ,sections of plagioclase crystals 7probably labradorite7 from the lava of #ahee4 ,mag41 #ajj diams4 #ad4 ,section of olivine crystal from the lava of #afca--;imperfectly formed4 ,mag41 #cj diams4 #ae4 ,section of mica-flake from the lava of #ahbb4 ,mag41 #cj diams4 ,illustration3 ,plate ,,iii4 ,,explanation ,,of ,,plate ,,iii4 ,,magnified ,,sections ,,of ,,volcanic ,,rocks4 #a4 ,diorite dyke1 traversing ,assynt limestone1 ,north ,highlands4 #b4 ,basalt from upper beds1 near ,giant's ,causeway1 ,county ,antrim4 #c4 ,hornblende-hypersthene-augite ,andesite1 from ,pichupichu1 ,andes4 #d4 ,augite-,andesite from ,pichupichu1 ,andes4 #e4 ,olivine dolerite1 with hornblende and biotite1 ,madagascar4 #f4 ,leucite basalt1 with mellilite1 ,capo di ,bove1 ,italy4 ,illustration3 ,plate ,,iv4 ,,explanation ,,of ,,plate ,,iv4 ,,magnified ,,sections ,,of ,,volcanic ,,rocks4 #a4 ,vesuvian lava1 glass paste with numerous crystals of leucite2 others of augite and nepheline porphyritically developed2 also small grains of magnetite4 #b4 ,vesuvian lava1 glass paste with numerous crystals of leucite2 others of olivine1 hornblende1 and sanidine1 porphyritically developed2 small grains of magnetite4 #c4 ,trachyte from ,hungary2 felsitic paste with crystals of hornblende and sanidine1 and a little magnetite4 #d4 ,gabbro1 from ,carlingford ,hill1 ,ireland1 consisting of anorthite1 augite1 a little olivine1 and magnetite4 #e4 ,dolerite1 from old volcanic neck1 ,scalot ,hill1 near ,lame1 consisting of labradorite1 augite1 olivine1 and magnetite4 #f4 ,dolerite1 ,ballintoy1 ,county ,antrim1 showing ophetic structure1 consisting of augite1 labradorite1 and magnetite4 #a ,mr4 ,s4 ,allport has discovered this in the rock called the ,wolf ,rock off the coast of ,cornwall4 ,the most important work on basalt is that by ,f4 ,zirkel1 ,unters4 ber mikros4 ,zusammensetzung und ,structur der ,basaltgesteine4 ,bonn 7#ahgj74 #b ,zirkel1 ,die mikroskopische ,beschaffenheit der ,mineralien und ,gesteine1 p4 #aec4 ,leipsig 7#ahgc74 #c ,zirkel1 ,petrog41 i4 #egh2 ,b4 von ,cotta1 p4 #agh 7,eng4 ,trans474 ,,index4 ,,index4 ,abyssinian table-lands1 #aij et seq4 ,albano1 ,lake1 #hi ,america1 volcanic regions of ,north1 #acf et seq42 of ,western1 #add ,andes1 #ah1 #bg1 #bbg1 #bed ,andesite1 #bfc ,antrim1 #aed et seq4 ,arabia1 dormant volcanoes of1 #abf-ace ,arabian desert1 #acd ,archibald1 ,c4 ,d41 #bac ,arizona1 volcanoes of1 #acg ,argyll1 ,duke of1 #agc ,ascension1 #cf ,ashangi1 volcanic series of1 #aib ,atmospheric effects of ,krakatoa eruption1 #bac-bad ,auckland district1 volcanoes of1 #adg ,auvergne1 volcanic regions of1 #ad1 #af1 #ib et seq4 ,azores1 #cb ,ball1 ,sir ,r4 ,s41 #bdb1 #bdd ,basalt1 #bfj ,blanford1 ,w4 ,t41 #ahh1 #ahi ,bonneville1 ,lake1 #ada-adb ,british ,isles1 ,tertiary volcanic districts of1 #aed et seq41 #bbg2 pre-,tertiary volcanic districts of1 #aif et seq4 ,buch1 ,l4 von1 #f1 #aa1 #bd ,california1 volcanoes of1 #adj ,callirrho1 springs of1 #acc ,caon1 the ,grand1 #ach ,cantal1 volcanoes of the1 #ii-aja ,cape ,colony1 ,basalts of1 #aid ,charleston earthquake1 #bah1 #bbb1 #bbd ,chambers1 ,g4 ,f41 #bdf ,charnwood ,forest1 #aih ,chimborazo1 #ah ,clermont1 vale of1 #if-ig ,clinkstone1 #bfc ,cordilleras of ,quito1 #be ,cotopaxi1 #af-ah1 #bd1 #bf ,crater-cones1 ,lava1 #ai ,crateriform cones1 #ac ,craterless domes1 #ae ,dana1 ,prof4 ,j4 ,d41 #ai1 #ci1 #bdi ,darwin1 #bh1 #cj ,darwin1 ,prof4 ,g4 ,h41 #i1 #bca ,daubeny1 #g1 #fa1 #fi ,davison1 ,c41 #i1 #bca ,davy1 ,sir ,h41 #aa ,deccan trap-series1 #ahg et seq4 ,demavend1 ,mount1 #bd ,diabase1 #bfb ,diorite1 #bfa ,dolerite1 #bfa ,domite1 #bfc ,dore1 volcanoes of ,mont1 #ajj-aja ,doughty1 ,c4 ,m41 #abg ,durocher1 #bcb ,dutton1 ,capt4 ,c4 ,e41 #i1 #bbj1 #bbb ,dykes in ,ireland1 #afi-agj ,earthquakes1 #bag et seq4 ,errigal1 #aj ,etna1 #ad1 #fa et seq41 #bbi ,fingal's ,cave1 #ahe ,forbes1 ,d41 #bg ,france1 extinct volcanoes of1 #ib et seq4 ,gabbro1 #bfa ,gardner1 ,j4 ,s41 #aef ,geikie1 ,sir ,a41 #h1 #bi1 #adc1 #aef1 #afj1 #afi1 #agb1 #agf1 #agg1 #aif ,giant's ,causeway1 #afe-aff ,granite1 #bfd ,granophyre1 #bfd2 of ,mull1 #agd ,green1 ,prof4 ,a4 ,h41 #aid ,hatch1 ,dr41 #bfj ,haughton1 ,prof41 #fh ,haurn1 volcanoes of the1 #bb1 #abi ,haute ,loire1 volcanic districts of1 #aja-aje ,hawaii1 volcanoes of1 #ci1 #bdi1 #bea ,hecla1 #cb ,herschel1 ,sir ,j41 #bdd ,hibbert1 ,dr4 ,s41 #f1 #aad1 #abd ,hochstetter1 ,f4 von1 #adg ,hopkins1 #aga1 #bag ,hull1 ,dr4 ,e4 ,g41 #aaj ,humboldt1 ,a4 von1 #bj1 #be ,hutton1 ,james1 #e ,iceland1 volcanoes of1 #cj-cb ,ireland1 volcanic ,tertiary rocks of1 #aed et seq4 ,jauln1 #abi ,johnston-,lavis1 #eb ,jordan valley1 #abf et seq41 #bbf ,jorullo1 #bd ,judd1 ,prof41 #h1 #fh1 #fi1 #ga1 #agb1 #agh1 #bjh ,krakatoa1 eruption of1 #bjf et seq4 ,kurile ,islands1 volcanoes of1 #bh ,laacher ,see1 #aba-abc ,lampophyre1 #bfb ,lancerote1 #cd ,lasaulx1 ,prof4 von1 #fh ,lavas1 relative density of1 #bcb-bcd ,lima in #agdf1 earthquake of1 #bbb ,lipari ,islands1 volcanoes of1 #fi et seq4 ,lisbon1 earthquake of1 #bba ,lister1 ,j4 ,j41 #ch ,lunar volcanoes1 #bcf et seq4 ,lyell1 ,sir ,c41 #cj1 #fb1 #gh1 #bag ,mackowen1 ,col41 #gd ,magdala1 volcanic series of1 #aib-aic ,mallet1 ,r41 #i1 #bag ,mauna ,loa1 #ai1 #ci1 #bdi ,mica-trap1 #bfb ,milne1 ,prof41 #bh1 #bah1 #bec ,moab1 volcanic regions of1 #acb ,moon1 volcanoes of1 #bcf et seq4 ,monte ,nuovo1 #he ,mull1 #agb et seq4 ,neapolitan group of volcanoes1 #bh ,new ,zealand1 volcanoes of1 #adf ,obsidian1 #bfd ,ocean waves of seismic origin1 #bjh1 #bbj ,o',reilly1 ,prof41 #i1 #bai ,orizaba1 #ba ,ovid1 #c ,pacific1 volcanic islands of1 #cg ,palestine1 dormant volcanoes of1 #abf-ace ,palmieri1 ,prof41 #ee ,pantelleria1 #gd ,phlegran fields1 #he ,phonolite1 #bfc ,pitchstone1 #bfd ,pliny1 #b1 #d ,porphyrite1 #bfb ,powell1 ,major1 #ach ,pre-,tertiary volcanic rocks1 #ahg et seq42 of ,british ,isles1 #aif et seq4 ,puy de ,dme1 #aje-aaj ,pythagoreans on volcanoes1 #b-c ,quito1 ,cordilleras of1 #be ,rangitoto1 #ai1 #adi ,reyer1 ,dr4 ,e41 #ag ,rhine valley1 volcanoes of1 #aac et seq4 ,rhyolite1 #bfc ,riviera in #ahhg1 earthquake of1 #bai ,rocca ,monfina1 #hj ,roderberg1 #aai1 #abj ,rome1 #hh-hi ,rosenbusch1 ,h41 #bfj ,roto ,mahana1 #aea ,ruapahu1 #aea ,russell1 ,hon4 ,rollo1 #bac ,rutley1 ,f41 #bfj ,st4 ,helena1 #cg ,san ,francisco1 ,mount1 #ach ,santorin1 #gf-hc ,schehallion1 #aj ,schumacher1 #abg ,scotland1 volcanic districts of1 #agb et seq4 ,scrope1 ,poulett1 #e1 #gc1 #ic1 #ih ,scuir of ,eigg1 #ahj-ahd ,seismic phenomena1 special1 #bja et seq41 #bag et seq4 ,shasta1 ,mount1 #adj ,siebengebirge1 #aaf-abj ,skye1 #agg-agi ,sleamish1 #afh ,smyth1 ,piazzi1 #cc ,snake ,river1 volcanoes of1 #adb ,staffa1 #ahe-ahf ,strabo on volcanoes1 #c ,stromboli1 #ga-gc ,sumatra1 volcanic action in1 #bbf ,syenite1 #bfb ,symes1 ,r4 ,g41 #afg ,syria1 earthquakes in1 #bai ,taupo ,lake1 #aej ,taylor1 ,mount1 #ach ,tell el ,ahmr1 #aca ,tell el ,akkasheh1 #aca ,tell el ,farras1 #aca ,tell ,ab en ,ned1 #acj ,tell ,ab ,nedr1 #abi ,templepatrick1 quarry at1 #afj ,teneriffe1 #cc ,tertiary period1 volcanic activity of1 #bee ,thucydides1 #b ,tonga ,islands1 volcanoes of1 #ch ,tongariro1 #aea ,trachyte1 #bfc ,trass of ,brhl ,valley1 #abc-abe ,tristan da ,cunha1 #cg ,tristram1 ,canon1 #abg1 #aca ,utah1 volcanoes of1 #acg ,verbeek1 ,r4 ,d4 ,m41 #bjb ,vesuvius1 #d1 #ad1 #da-fj1 #fg1 #bbi ,volcanoes1 historic notices of1 #a-e2 form1 structure1 and composition of1 #aj-ai2 lines and groups of active1 #bj-bi2 of mid-ocean1 #cj-dj2 extinct or dormant1 #hd et seq42 special volcanic and seismic phenomena1 #bja et seq42 the ultimate cause of volcanic action1 #bbe et seq42 whether we are living in an epoch of special volcanic activity1 #bec-bef2 brief account of volcanic rocks1 #bei-bfe ,vulcanists1 #e ,vulcano1 #fi1 #ga ,wallace1 ,a4 ,r41 #ha ,waltershausen1 ,w4 ,s4 von1 #g1 #fa ,wellington1 ,mount1 #adi ,wharton1 ,capt41 #bab ,whymper1 ,e41 #ah ,yarmk1 valley of the1 #abi1 #aca ,yellowstone ,park1 #ade ,zirkel1 ,f41 #bfj ,zllner1 #bdj ,,the ,,walter ,,scott ,,press1 ,,newcastle-,,on-,,tyne4 ,the ,contemporary ,science ,series4 ,,edited ,,by ,,havelock ,,ellis4 99 99 99 99 99 ,crown #hvo1 ,cloth1 #cs4 #f;d4 per vol42 ,half ,morocco1 #fs4 #f;d4 ,i4 ,,the ,,evolution ,,of ,,sex4 ,by ,professor ,,patrick ,,geddes and ,j4 ,,arthur ,,thomson4 ,with #ij ,illustrations4 ,second ,edition4 ,the authors have brought to the task--as indeed their names guarantee--a wealth of knowledge1 a lucid and attractive method of treatment1 and a rich vein of picturesque language4--,nature4 ,,ii4 ,,electricity ,,in ,,modern ,,life4 ,by ,g4 ,w4 ,,de ,,tunzelmann4 ,with #hh ,illustrations4 ,a clearly-written and connected sketch of what is known about electricity and magnetism1 the more prominent modern applications1 and the principles on which they are based4--,saturday ,review4 ,,iii4 ,,the ,,origin ,,of ,,the ,,aryans4 ,by ,dr4 ,,isaac ,,taylor4 ,illustrated4 ,second ,edition4 ,canon ,taylor is probably the most encyclopdic all-round scholar now living4 ,his new volume on the ,origin of the ,aryans is a first-rate example of the excellent account to which he can turn his exceptionally wide and varied information4444 ,masterly and exhaustive4--,pall ,mall ,gazette4 ,,iv4 ,,physiognomy ,,and ,,expression4 ,by ,p4 ,,mantegazza4 ,illustrated4 ,professor ,mantegazza is a writer full of life and spirit1 and the natural attractiveness of his subject is not destroyed by his scientific handling of it4--,literary ,world 7,boston74 ,v4 ,,evolution ,,and ,,disease4 ,by ,j4 ,b4 ,,sutton1 ,f4,r4,c4,s4 ,with #ace ,illustrations4 ,the work is of special value to professional men1 yet educated persons generally will find much in it which it is both interesting and important to know4--,the ,scottish ,weekly4 ,,vi4 ,,the ,,village ,,community4 ,by ,g4 ,l4 ,,gomme4 ,illustrated4 ,his book will probably remain for some time the best work of reference for facts bearing on those traces of the village community which have not been effaced by conquest1 encroachment1 and the heavy hand of ,roman law4--,scottish ,leader4 ,,vii4 ,,the ,,criminal4 ,by ,,havelock ,,ellis4 ,illustrated4 ,an ably written1 an instructive1 and a most entertaining book4--,law ,quarterly ,review4 99 99 99 99 99 ,london3 ,,walter ,,scott1 ,,limited1 #bd ,warwick ,lane4 ,the ,contemporary ,science ,series--continued4 ,,viii4 ,,sanity ,,and ,,insanity4 ,by ,dr4 ,,charles ,,mercier4 ,illustrated4 ,taken as a whole1 it is the brightest book on the physical side of mental science published in our time4--,pall ,mall ,gazette4 ,,ix4 ,,hypnotism4 ,by ,dr4 ,,albert ,,moll4 ,second ,edition4 ,marks a step of some importance in the study of some difficult physiological and psychological problems which have not yet received much attention in the scientific world of ,england4--,nature4 ,x4 ,,manual ,,training4 ,by ,dr4 ,c4 ,m4 ,,woodward1 ,director of the ,manual ,training ,school1 ,st4 ,louis4 ,illustrated4 ,there is no greater authority on the subject than ,professor ,woodward4--,manchester ,guardian4 ,,xi4 ,,the ,,science ,,of ,,fairy ,,tales4 ,by ,e4 ,,sidney ,,hartland4 ,mr4 ,hartland's book will win the sympathy of all earnest students1 both by the knowledge it displays1 and by a thorough love and appreciation of his subject1 which is evident throughout4--,spectator4 ,,xii4 ,,primitive ,,folk4 ,by ,,elie ,,reclus4 ,for an introduction to the study of the questions of property1 marriage1 government1 religion1--in a word1 to the evolution of society1--this little volume will be found most convenient4--,scottish ,leader4 ,,xiii4 ,,the ,,evolution ,,of ,,marriage4 ,by ,professor ,,letourneau4 ,among the distinguished ,french students of sociology1 ,professor ,letourneau has long stood in the first rank4 ,he approaches the great study of man free from bias and shy of generalisations4 ,to collect1 scrutinise1 and appraise facts is his chief business4--,science4 ,,xiv4 ,,bacteria ,,and ,,their ,,products4 ,by ,dr4 ,g4 ,,sims ,,woodhead4 ,illustrated4 ,an excellent summary of the present state of knowledge of the subject4--,lancet4 ,,xv4 ,,education ,,and ,,heredity4 ,by ,j4 ,m4 ,,guyau4 ,it is a sign of the value of this book that the natural impulse on arriving at its last page is to turn again to the first1 and try to gather up and coordinate some of the many admirable truths it presents4--,anti-,jacobin4 ,,xvi4 ,,the ,,man ,,of ,,genius4 ,by ,professor ,,lombroso4 ,illustrated4 ,by far the most comprehensive and fascinating collection of facts and generalisations concerning genius which has yet been brought together4--,journal of ,mental ,science4 ,,xvii4 ,,the ,,grammar ,,of ,,science4 ,by ,professor ,,karl ,,pearson4 ,illustrated4 ,,xviii4 ,,property3 ,,its ,,origin ,,and ,,development4 ,by ,,ch4 ,,letourneau1 ,general ,secretary to the ,anthropological ,society1 ,paris1 and ,professor in the ,school of ,anthropology1 ,paris4 ,an ethnological account of the beginnings of property among animals1 of its communistic stages among primitive races1 and of its later individualistic developments1 together with a brief sketch of its probable evolution in the future4 99 99 99 99 99 ,london3 ,,walter ,,scott1 ,,limited1 #bd ,warwick ,lane4 99 99 99 99 99 ,transcriber's note3 ,changed ',kilarrea' to ',kilauea' on page #ai3 ,mauna ,loa and ,kilarrea4 ,changed ',kilanea' to ',kilauea' on page #ci3 ,kilanea1 #daeh feet4 ,made punctuation 7semi-colons7 consistent in caption to figure #af4 ,changed ',brionde' to ',brioude' on page #id3 till at ,brionde it becomes4 ,changed 'occuping' to 'occupying' on page #if3 occuping a hollow4 ,changed ',rodesberg' to ',roderberg' on page #aah3 old extinct volcano of ,rodesberg4 ,changed ',wolkenberg' to ',wolkenburg' on page #aah3 and that of the ,wolkenberg4 ,left the reference to ,jeremiah1 l4 #be4 in footnote to ,part ,,iii ,chapter ,i1 although ,jeremiah1 li4 #be4 seems more appropriate4 ,changed 'fumarols' to 'fumaroles' on page #acg3 fumarols give evidence4 ,removed extra comma on page #aec3 of the present1 epoch4 ,changed 'columnal' to 'columnar' on page #agf3 the columnal structure4 ,changed 'groves' to 'grooves' on page #ahc3 the groves and scorings4 ,changed ',angust' to ',august' on page #bab3 the #bgth of ,angust4 ,changed 'mikroskopischen' to 'mikroskopische' on page #bfj3 ber mikroskopischen ,structur4 ,changed 'become' to 'becomes' on page #bfj3 the rock become a leucite-basalt4 ,left inconsistent spellings of ',baalbec' and ',baalbeck'2 ',harrat' and ',harrt'2 'mtres' and 'metres'2 'pitchstone' and 'pitch-stone'2 'prehistoric' and 'pre-historic'2 ',rhne' and ',rhone'2 'sub-aerial'1 'subarial' and 'subaerial'2 'tableland' and 'table-land'4 ,greek words were replaced with their transliterations3 'meson pyr' and ',peri kosmou'4 ,the oe-ligature was expanded to the two separate characters3 ',euboea' and ',boeotia'4 ,left the list numbering as is at the beginning of ,chapter ,,ii of ,part ,,iv1 even though the list begins at item c1 as if it continues the list which began in the previous chapter4