,,the ,,eruption ,,of ,,vesuvius ,,in   
#ahgb1   ,,by ,,professor ,,luigi       
,,palmieri1 ,of the ,university of      
,naples2 ,director of the ,vesuvian     
,observatory4   ,,with ,,notes1 ,,and   
,,an ,,introductory ,,sketch ,,of ,,the 
,,present ,,state ,,of ,,knowledge ,,of 
,,terrestrial ,,vulcanicity1 ,the       
,cosmical ,nature and ,relations of     
,volcanoes and ,earthquakes4   ,,by     
,,robert ,,mallet1 ,mem4 ,inst4 ,c4,e41 
,f4,r4,s41 ,f4,g4,s41 ,m4,r4,i4,a41 c41 
c4   ,,with ,,illustrations4   ,,london3
  ,,asher  ,,co41 #ac1 ,,bedford        
,,street1 ,,covent ,,garden1 ,w4,c4     
#ahgc4   ,w4 ,s4 ,johnson1 ,nassau      
,steam ,press1 #fj1 ,st4 ,martin's      
,lane1 ,charing ,cross1 ,w4,c4   ,the   
,translator should look upon himself as 
a ,merchant in the ,intellectual        
,exchange of the world1 whose business  
it is to promote the interchange of the 
produce of the mind4                    
,,goethe1 ,kunst und ,alterthum4        
,,introductory ,,sketch1 c4   ,the      

publishers of this little volume1 in    
requesting me to undertake a translation
 of the ,incendio ,vesuviano1 of        
,professor ,palmieri1 and to accompany  
it with some introductory remarks1 have 
felt justified by the facts that ,signor
 ,palmieri's position as a physicist1   
the great advantages which his long     
residence in ,naples as a ,professor of 
the ,university1 and for many years past
 ,director of the ,meteorological       
,observatory--established upon ,vesuvius
 itself1 prior to the expulsion of the  
late dynasty--have naturally caused much
 weight to attach to anything emanating 
from his pen in reference to that       
volcano4  ,nearly forty memoirs on      
various branches of physics--chiefly    
electricity1 magnetism and              
meteorology--produced since #ahdb1 are  
to be found under ,palmieri's name in   
the ,universal ,catalogue of ,scientific
 ,papers of the ,royal ,society1 and of 
these nine refer to ,vesuvius1 the      
earliest being entitled ,primi ,studii  

,meteorologici fatti sul ,r4            
,osservatorio ,vesuviano1 published in  
#ahec4 ,he was also author1 in          
conjunction with ,professor ,a4         
,scacchi1 of an elaborate report upon   
the ,volcanic ,region of ,monte         
,vulture1 and on the ,earthquake        
7commonly called of ,melfi7 of #ahea4   
,these1 however1 by no means exhaust the
 stock of ,palmieri's labours4  ,the    
following ,memoir of ,signor ,palmieri  
on the eruption of ,vesuvius in ,april  
of this year 7#ahgb71 brief as it is1   
embraces two distinct subjects1 viz41   
his narrative as an eye-witness of the  
actual events of the eruption as they   
occurred upon the cone and slopes of the
 mountain1 and his observations as to   
pulses emanating from its interior1 as  
indicated by his ,seismograph1 and as to
 the electric conditions of the         
overhanging cloud of smoke 7so called7  
and ashes1 as indicated by his bifilar  
electrometer1 both established at the   
,observatory4 ,the two last have but an 

indirect bearing upon ,vulcanology4 ,the
 narrative of the events of the eruption
 is characterised by exactness of       
observation and a sobriety of           
language--so widely different from the  
exaggerated style of sensational writing
 that is found in almost all such       
accounts--that ,i do the author no more 
than justice in thus expressing my view 
of its merits4  ,nor should a special   
narration1 such as this1 become less    
important or suffer even in popular     
estimation by the fact that so recently 
my friend1 ,professor ,j4 ,phillips1 has
 given to the world the best general    
account of ,vesuvius1 in its historical 
and some of its scientific aspects1     
which has yet appeared4 ,that           
monograph--with its sparkling style1 and
 scholarly digressions1 as well as for  
its more direct merits--will1 no doubt1 
become the manual for many a future     
visitor to the volcanic region of       
,naples2 but it1 like the following     
,memoir of ,palmieri1 and in common with

 almost every work that has appeared on 
the subject of ,volcanoes1 contains a   
good deal which1 however interesting1   
and remotely related to ,vulcanology1   
does not properly belong to the body of 
that branch of cosmical science1 as ,i  
understand its nature and limits4  ,it  
tends but little1 for example1 to clear 
our views1 or enlarge our knowledge of  
the vast mechanism in which the ,volcano
 originates1 and that by which its      
visible mass is formed1 that we should  
ascertain the electric condition of the 
atmosphere above its eruptive cone1 or  
into what crystallographic classes the  
mineral species found about it may be   
divided3 it will help us but little to  
know ,pliny's notions of how ,pompeii   
was overwhelmed1 or to re-engrave       
pictures1 assumed to give the exact     
shape of the ,vesuvian or other cone at 
different periods1 or its precise       
altitude1 which are ever varying1 above 
the sea4 ,even much more time and labour
 may be spent upon analysing the vapours

 and gases of fumaroles and salfatares  
than the results can now justify4       
,nothing1 perhaps1 tends more to the    
effective progress of any branch of     
observational and inductive science1    
than that we should endeavour to discern
 clearly the scope and boundary of our  
subject4  ,to do so is but to accord    
with ,bacon's maxim1 ,prudens questio   
dimidium scienti4 ,that once shaped1 the
 roads or methods of approach become    
clearer2 and every foothold attained    
upon these direct paths enables us to   
look back upon such collateral or       
subordinate questions as at first       
perplexed us1 and find them so          
illuminated that they are already       
probably solved1 and1 by solution1 again
 prove to us that we are in the right   
paths4  ,i believe1 therefore1 that ,i  
shall not do disservice to the grand    
portion of cosmical physics to which    
volcanic phenomena belong1 by devoting  
the few pages accorded to me for this   
,introduction to sketching what seems to

 me to be the present position of       
terrestrial ,vulcanicity1 and tracing   
the outlines and relations of the two   
branches of scientific                  
investigation--,vulcanology and         
,seismology--by which its true nature   
and part in the ,cosmos are chiefly to  
be ascertained4  ,the general term1     
,vulcanicity1 properly comprehends all  
that we see or know of actions taking   
place upon and modifying the surface of 
our globe1 which are referable not to   
forces of origin above the surface1 and 
acting superficially1 but to causes that
 have been or are in operation beneath  
it4 ,it embraces all that ,humboldt has 
somewhat vaguely called the reactions of
 the interior of a planet upon its      
exterior4  ,these reactions show        
themselves principally and mainly in the
 marking out and configuration of the   
great continents and ocean beds1 in the 
forcing up of mountain chains1 and in   
the varied phenomena consequent thereon1
 as seen in more or less adjacent       

formations4  ,these constitute the      
mechanism which has moulded and         
fashioned the surface of our globe from 
the period when it first became         
superficially solid1 and prepared it as 
the theatre for the action of all those 
superficial actions--such as those of   
tides1 waves1 rain1 rivers1 solar heat1 
frost1 vitality1 vegetable and animal   
7passing by many others less            
obvious7--which perpetually modify1     
alter or renew the surface of our world1
 and maintain the existing regimen of   
the great machine1 and of its           
inhabitants4 ,these last are the domain 
of ,geology1 properly so called4 ,no    
geological system can be well founded1  
or can completely explain the working of
 the world's system as we now see it1   
that does not start from ,vulcanicity as
 thus defined2 and this is equally true1
 whether1 as do most geologists1 we     
include within the term ,geology        
everything we can know about our world  
as a whole1 exclusive of what ,astronomy

 teaches as to it1 dividing ,geology in 
general into ,physical ,geology--the    
boundaries of which are very            
indistinct--and ,stratigraphical        
,geology1 whose limits are equally so4  
,it has been often said that ,geology in
 this widest sense begins where         
,astronomy or ,cosmogony ends its       
information as to our globe1 but this is
 scarcely true4  ,vulcanicity--or       
,geology1 if we choose to make it       
comprehend that--must commence its      
survey of our world as a nebula upon    
which1 for unknown ages1 thermic1       
gravitant and chemical forces were      
operative1 and to the final play of     
which1 the form1 density and volume1 as 
well as order of deposition of the      
different elements in the order of their
 chemical combination and deposition was
 due1 when first our globe became a     
liquid or partly liquid spheroid1 and   
which have equally determined the       
chemical nature of the materials of the 
outward rind of the earth that now is1  

and with these some of the primary      
conditions that have fixed the          
characters1 nature and interdependence  
of the vegetables and animals that      
inhabit it4 ,physical ,astronomy and    
,physical ,geology1 through             
,vulcanicity1 thus overlap each other2  
the first does not end where the second 
begins2 and in every sure attempt to    
bring ,geology to that pinnacle which is
 the proper ideal of its completed      
design--namely1 the interpretation of   
our world's machine1 as part of the     
universal ,cosmos 7so far as that can   
ever become known to our limited        
observation and intelligence7--we must  
carry with us astronomic considerations1
 we must keep in view events anterior to
 the status consistentior of ,leibnitz1 
nor lose sight of the fact that the     
chain of causation is one endless and   
unbroken2 that forces first set moving1 
we know not when or how1 the dim        
remoteness of which imagination tries to
 sound in shadowy thought1 like those of

 the grand old ,eastern poem1 ,when the 
morning stars first sang together1 are1 
however changed in form1 operative      
still4 ,the light and fragile butterfly1
 whose glorious garb irradiates the     
summer zephyr in which it floats1 has   
had its power of flight--which is its   
power to live--determined by results of 
that same chain of causes that lifted   
from the depths the mountain on whose   
sunny side he floats1 that has          
determined the seasons and the colour of
 the flower whose nectar he sucks1 and  
that discharges or dissipates the storm 
above1 that may crush the insect and the
 blossom in which it basked4 ,and thus1 
as has been said1 it was not all a myth1
 that in older days affirmed that in    
some mysterious way the actions and the 
lives of men were linked to the stars in
 their courses4  ,whatever may have been
 the manifestations of ,vulcanicity at  
former and far remoter epochs of our    
planet1 and to which ,i shall return1 in
 the existing state of regimen of and   

upon our globe it shows itself chiefly  
in the phenomena of ,volcanoes and of   
,earthquakes1 which are the subjects of 
,vulcanology and of ,seismology         
respectively1 and in principal part1    
also1 of this ,introduction4  ,the      
phenomena of hot springs1 geysers1 etc41
 which might be included under the title
 of ,thermopgology1 have certain        
relations to both1 but more immediately 
to ,vulcanology4  ,let us now glance at 
the history and progress of knowledge in
 these two chief domains of             
,vulcanicity1 preparatory to a sketch of
 its existing stage as to both1 and1 by 
the way1 attempt to extract a lesson as 
to the methods by which such success as 
has attended our labours has been       
achieved4  ,it will be most convenient  
to treat of ,seismology first in order4 
,aristotle--who devotes a larger space  
of his ,fourth ,book1 ,greek3 ,peri     
,kosmou1 to ,earthquakes--,seneca1      
,pliny1 ,strabo1 in the so-called       
classic days1 and thence no end of      

writers down to about the end of the    
seventeenth century--amongst whom       
,fromondi 7#aebg7 and ,travagini 7#afgi7
 are1 perhaps1 the most important       
now--have filled volumes with records of
 facts1 or what they took to be such1 of
 ,earthquakes1 as handed down to or     
observed by themselves1 and with plenty 
of hypotheses as to their nature and    
origin1 but sterile of much real        
knowledge4  ,hooke's ,discourses of     
,earthquakes1 read before the ,royal    
,society about #afij1 afford a curious  
example of how abuse of words once given
 by authority clings as a hindrance to  
progress4 ,he had formed no distinct    
idea of what he meant by an ,earthquake1
 and so confusedly mixes up all         
elevations or depressions of a permanent
 character with subversions1 conversions
 and transpositions of parts of the     
earth1 however sudden or transitory1    
under the name of ,earthquakes4  ,a like
 confusion is far from uncommon amongst 
geological writers1 even at the present 

day1 and examples might be quoted from  
very late writings of even some of the  
great leaders of ,english ,geology4     
,from the seventeenth to the middle of  
the eighteenth century one finds floods 
of hypotheses from ,flamsteed1          
,httinger1 ,amontons1 ,stukeley1        
,beccaria1 ,percival1 ,priestly1 and a  
crowd of others1 in which electricity1  
then attracting so much attention1 is   
often called upon to supply causation   
for a something of which no clear idea  
had been formed4 ,count ,bylandt's      
singular work1 published in #ahce1      
though showing a curious partial insight
 in point of advancement1 might be put  
back into that preceding period4  ,in   
#agfj appeared the very remarkable      
,paper1 in the fifty-first volume of the
 ,philosophical ,transactions1 of the   
,rev4 ,john ,mitchell1 of ,cambridge1 in
 which he views an ,earthquake as a     
sudden lifting up1 by a rapid evolution 
of steam or gas beneath1 of a portion of
 the earth's crust1 and the lateral     

transfer of this gaseous bubble beneath 
the earth's crust1 bent to follow its   
shape and motion1 or that of a wave of  
liquid rock beneath1 like a carpet      
shaken on air4 ,great as are certain    
collateral merits of ,mitchell's ,paper1
 showing observation of various sorts   
much in advance of his time1 this notion
 of an ,earthquake is such as1 had he   
applied to it even the imperfect        
knowledge of mechanics and physics then 
possessed in a definite manner1 he could
 scarcely have failed to see its        
untenable nature4 ,that the same notion1
 and in a far more extravagant form1    
should have been reproduced in #ahdc by 
,messrs4 ,rogers1 by whom the gigantic  
parallel anticlinals1 flanks and valleys
 of the whole ,appalachian chain of     
mountains are taken for nothing more    
than the indurated foldings and wrinkles
 of ,mitchell's carpet1 is one of the   
most salient examples of the abuse of   
hypothesis untested by exact science4   
,neither ,humboldt nor ,darwin1 great as

 were the opportunities of observation  
enjoyed by both1 can be supposed to have
 formed any definite idea of what an    
,earthquake is2 and the latter1 who had 
observed well the effects of great      
sea-waves rolling in-shore after the    
shock1 did not establish any clear      
relation between the two4,a  ,hitherto  
no one appears to have formed any clear 
notion as to what an ,earthquake        
is--that is to say1 any clear idea of   
what is the nature of the movement      
constituting the shock1 no matter what  
may be the nature or origin of the      
movement itself4 ,the first glimmering  
of such an idea1 so far as my reading   
has enabled me to ascertain1 is due to  
the penetrating genius of ,dr4 ,thomas  
,young1 who1 in his ,lectures on        
,natural ,philosophy1 published in      
#ahjg1 casually suggests the probability
 that earthquake motions are vibratory1 
and are analogous to those of sound4,b  
,this was rendered somewhat more        
definite by ,gay ,lussac1 who1 in an    

able paper ,on the ,chemical ,theories  
of ,volcanoes1 in the twenty-second     
volume of the ,annales de ,chmie1 in    
#ahbc1 says3 ,en un mot1 les            
tremblements de terre ne sont que la    
propagation d'une commotion  travers la 
masse de la terre1 tellement indpendante
 des cavits souterraines qu'elle        
s'entendrait1 d'autant plus loin que la 
terre serait plus homogne4  ,these      
suggestions of ,young and of ,gay       
,lussac1 as may be seen1 only refer to  
the movement in the more or less solid  
crust of the earth4 ,but two1 if not    
three1 other great movements were long  
known to frequently accompany earthquake
 shocks--the recession of the sea from  
the shore just about the moment of      
shock--the terrible sounds or           
subterraneous growlings which sometimes 
preceded1 sometimes accompanied1 and    
sometimes followed the shock--and the   
great sea-wave which rolls in-shore more
 or less long after it1 remained still  
unknown as to their nature4 ,they had   

been recognised only as concomitant but 
unconnected phenomena--the more         
inexplicable1 because sometimes present1
 sometimes absent1 and wholly without   
any known mutual bearing or community of
 cause4  ,on the #ith ,february1 #ahdf1 
,i communicated to the ,royal ,irish    
,academy my ,paper1 ,on the ,dynamics of
 ,earthquakes1 printed in ,vol4 ,,xxi41 
,part ,i41 of the ,transactions of that 
,academy1 and published the same year in
 which it was my good fortune to have   
been able to colligate the observed     
facts1 and bringing them together under 
the light of the known laws of          
production and propagation of vibratory 
waves in elastic1 solid1 liquid and     
gaseous bodies1 and of the production   
and propagation of liquid waves of      
translation in water varying in depth1  
to prove that all the phenomena of      
earthquake shocks could be accounted for
 by a single impulse given at a single  
centre4 ,the definition given by me in  
that ,paper is that an earthquake is    

,the transit of a wave or waves of      
elastic compression in any direction1   
from vertically upwards to horizontally1
 in any azimuth1 through the crust and  
surface of the earth1 from any centre of
 impulse or from more than one1 and     
which may be attended with sound and    
tidal waves dependent upon the impulse  
and upon circumstances of position as to
 sea and land4  ,thus1 for example1 if  
the impulse 7whatever may be its cause7 
be delivered somewhere beneath the bed  
of the sea1 all four classes of         
earthquake waves may reach an observer  
on shore in succession4 ,the elastic    
wave of shock passing through the earth 
generally reaches him first3 its        
velocity of propagation depending upon  
the specific elasticity and the degree  
of continuity of the rocky or the       
incoherent formations or materials      
through which it passes4  ,under        
conditions pointed out by me1 this      
elastic wave may cause an aqueous wave1 
producing recession of the sea1 just as 

it reaches the margin of sea and land4  
,if the impulse be attended by fractures
 of the earth's crust1 or other         
sufficient causes for the impulse to be 
communicated to the air directly or     
through the intervening sea1 ordinary   
sound-waves will reach the observer     
through the air1 propagated at the rate 
of #a1adj feet per second1 or           
thereabouts2 and may also reach him     
before or with or soon after the shock  
itself1 through the solid material of   
the earth2 and lastly1 if the impulse be
 sufficient to disturb the sea-bottom   
above the centre of impulse1 or         
otherwise to generate an aqueous wave of
 translation1 that reaches the observer 
last1 rolling in-shore as the terrible  
great sea-wave1 which has ended so many 
of the great earthquakes1 its dimensions
 and its rate of propagation depending  
upon the magnitude of the originating   
impulse and upon the variable depth of  
the water4 ,it is not my purpose1 nor   
would it be possible within my limits   

here1 to give any complete account of   
the matter contained in that ,paper1    
which1 in the words of the ,president of
 the ,academy upon a later occasion1    
fixed upon an immutable basis the true  
theory of ,earthquakes4,c ,i should     
state1 however1 that in it ,i proved the
 fallacy of the notion of vorticose     
shocks1 which had been held from the    
days of ,aristotle1 and showed that the 
effects 7such as the twisting on their  
bases of the ,calabrian ,obelisks7 which
 had been supposed due to such1 were but
 resolved motions1 due to the transit   
rectilinearly of the shock4  ,this      
removed one apparent stumbling block to 
the true theory4  ,incidentally also it 
was shown that from the observed        
elements of the movement of the elastic 
wave of shock at certain points--by     
suitable instruments--the position and  
depth of the focus1 or centre of        
impulse1 might be inferred4  ,in the    
same volume 7,transactions of the ,royal
 ,i4 ,academy1 ,,xxi47 ,i gave account1 

with a design to scale1 for the first   
self-registering and recording          
seismometer ever1 to my knowledge1      
proposed4 ,in some respects in principle
 it resembles that of ,professor        
,palmieri1 of which he has made such    
extended use at the ,vesuvian           
,observatory1 though it differs much    
from the latter in detail4 ,in ,june1   
#ahdg1 ,mr4 ,hopkins1 of ,cambridge1    
read his ,report1 ,on the ,geological   
,theories of ,elevation and             
,earthquakes1 to the ,british           
,association--requested by that body the
 year before--and printed in its        
,reports for that year4  ,the chief     
features of this document are a digest  
of ,mr4 ,hopkins's previously published 
,mathematical ,papers on the formations 
of fissures1 etc41 by elevations and    
depressions1 and those on the thickness 
of the earth's crust1 based on          
precession1 etc41 which he discusses in 
some relations to volcanic action4      
,this extends to forty-one pages1 the   

remaining eighteen pages of the ,report 
being devoted to ,vibratory ,motions of 
the ,earth's ,crust produced by         
,subterranean ,forces--,earthquakes4    
,the latter consists mainly of a rsum of
 the acknowledged laws1 as delivered    
principally by ,poisson1 of formation   
and propagation of elastic waves and of 
liquid waves1 by ,webers1 ,s4 ,russel   
and others--the original matter in this 
,report is small--and as respects the   
latter portion consists mainly in some  
problems for finding analytically the   
position or depth of the centre of      
disturbance when certain elements of the
 wave of shock are given1 or have been  
supposed registered by seismometric     
instruments1 such as that described by  
myself1 and above referred to4,d ,at the
 time my original ,paper ,on the        
,dynamics of ,earthquakes was published1
 there was little or no experimental    
knowledge as to the actual velocity of  
transit of waves--analogous to those of 
sound1 but of greater amplitude--through

 elastic solids4 ,the velocity as       
deduced from theory1 the solid being    
assumed quite homogeneous and           
continuous1 was very great1 and might be
 taken for some of the harder and denser
 rock formations at #aa1jjj or #ab1jjj  
feet per second4 ,that these enormous   
velocities of wave transit would be     
something near those of actual          
earthquake shock seemed probable to me1 
and was so accepted by ,hopkins4  ,thus1
 he says 7,report1 p4 #hh73 ,the        
velocity of the sea-wave1 for any       
probable depth of the sea1 will be so   
small as compared with that of the      
vibratory wave1 that we may consider the
 time of the arrival of the latter at   
the place of observation as coincident  
with that of the departure of the       
sea-wave from the centre of divergence4 
,in my original ,paper 7,dynamic1 c471  
,i had suggested1 as an important       
object1 to ascertain by actual          
experiment what might be the wave's     
transit rate in various rocky and       

incoherent formations2 and having       
proposed this in my first ,report upon  
the ,facts of ,earthquake to the        
,british ,association1 ,i was enabled by
 its liberality to commence those       
experiments1 in which ,i was ably       
assisted by my eldest son1 then quite a 
lad--,dr4 ,jno4 ,william ,mallet1 now   
,professor of ,chemistry at the         
,university of ,virginia1 ,u4,s42 and to
 give account of the results1 in my     
second ,report 7,report1 ,british       
,association for #ahea7 to that body4   
,those experiments were made by         
producing an impulse at one end of an   
accurately measured base line1 by the   
explosion of gunpowder in the formation 
experimented upon1 and noting the time  
the elastic wave generated required to  
pass over that distance1 upon a nearly  
level surface4 ,special instruments were
 devised and employed1 by which the     
powder was fired and the time           
registered1 by touching a lever which   
completed certain galvanic contacts4    

,the media or formations in which these 
experiments were conducted were1 damp   
sand--as likely to give the minimum     
rate--and crystalline rock 7granite71 as
 likely to give the maximum4 ,the       
results were received1 not with doubt1  
but with much surprise1 for it at once  
appeared that the actual velocity of    
transit was vastly below what theory had
 indicated as derivable from the density
 and modulus of elasticity of the       
material1 taken as homogeneous1 etc4    
,the actual velocities in feet per      
second found were3    ,in sand          
#hbdiae feet per second4   ,in          
discontinuous and     much shattered    
granite       #a1cjfdbe              ,in
 more solid granite          #a1ffdegd  
,this ,i at once attributed1 and as it  
has since been proved correctly1 to the 
loss of vis viva1 and consequently of   
speed1 by the discontinuity of the      
materials4  ,and some indication of the 
general truth of the fact was derivable 
from comparing the rude previous        

approximations to the transit rate of   
some great ,earthquakes4 ,in the case of
 that of ,lisbon1 estimated by ,mitchell
 at #a1gfj feet per second4 ,it was     
still desirable to extend similar       
experiments to the harder classes of    
stratified and of contorted rocks4 ,this
 ,i was enabled to carry into effect1 at
 the great ,quarries at ,holyhead       
7whence the slate and quartz rocks have 
been obtained for the construction of   
the ,asylum ,harbour there71 taking     
advantage of the impulses generated at  
that period by the great mines of powder
 exploded in these rocks4  ,the results 
have been published in the              
,philosophical ,transactions for #ahfa  
and #ahfb 7,appendix74 ,they show that  
the mean lowest rate of wave transit in 
those rocks1 through measured ranges of 
from #e1jch to #f1ehb feet1 was #a1jhi  
feet per second2 and the mean highest1  
#a1ceb feet per second2 and the general 
mean #a1cbj feet per second4  ,by a     
separate train of experiments on the    

compressibility of solid cubes of these 
rocks1 ,i obtained the mean modulus of  
elasticity of the material when         
perfectly continuous and unshattered1   
with this remarkable result--that in    
these rocks1 as they exist at ,holyhead1
 nearly seven-eighths of the full       
velocity of wave transmission due to the
 material1 if solid and continuous1 is  
lost by reason of the heterogeneity and 
discontinuity of the rocky masses as    
they are found piled together in        
,nature4  ,i also proved that the       
wave-transit period of the unshattered  
material of these rocks was greatest in 
a direction transverse to the bedding1  
and least in line parallel with that2   
but the effect of this in the rocky mass
 itself may be more than counterbalanced
 by the discontinuity and imperfect     
contact of the adjacent beds4  ,these   
results indicate1 therefore1 that the   
superficial rate of translation of the  
solitary sea-wave of earthquakes may1   
when over very deep water1 equal or even

 exceed the transit rate 7in some cases7
 of the elastic wave of shock itself4   
,these results have since received      
general confirmation by the careful     
determinations of the transit rates of  
actual earthquake waves1 in the rocks of
 the ,rhine ,country and in ,hungary1 by
 ,nggerath and ,schmidt respectively1   
and by those made since by myself in    
those of ,southern ,italy1 to which ,i  
shall again refer4 ,in an elastic wave  
propagated from a centre of impulse in  
an infinitely extended volume of a      
perfect gas1 normal vibrations are alone
 propagated--as is the case with sound  
in air4  ,in the case of like movements 
propagated in elastic and perfectly     
homogeneous and isotropic solids1 the   
wave possesses both normal and          
transversal vibrations1 and is1 in so   
far1 analogous to the case of light4    
,mr4 ,hopkins1 in his ,report above     
referred to1 has based certain          
speculations upon the assumed necessary 
co-existence of both orders of vibration

 in actual earthquake shocks in the     
materials of which our earthy crust is  
actually composed4  ,the existence of   
transversal vibration in those materials
 has not been yet proved experimentally1
 though there is sufficient ground to   
preclude our denying their probable     
existence4  ,that if they do exist they 
play but a very subordinate part in the 
observable phenomena of actual          
,earthquake is highly probable4 ,this is
 the view1 supported not only by        
observations of the effects of such     
shocks in ,nature1 but by the theoretic 
consideration of the effects of         
discontinuity of formations in planes or
 beds more or less transverse to the    
wave path 7or line joining the centre of
 impulse with the mean centre of wave   
disturbance at any point of its         
transit74 ,if we suppose1 for           
illustration sake1 such an elastic wave 
transmitted perpendicularly through a   
mass of glass plates1 each indefinitely 
thin1 and all in absolute contact with  

each other1 but without adhesion or     
friction1 more or less of the           
transversal vibration of the wave would 
be cut off and lost at each transit from
 plate to plate1 as the elastic         
compression can1 by the conditions1 be  
transmitted only normally or by direct  
push perpendicularly from plate to      
plate4 ,this must take place in ,nature1
 and to a very great extent1 and the    
consideration1 with others1 enabled me  
generally to apply the normal wave      
motion of shock alone to my             
investigation as to the depth of the    
centre of impulse of the great          
,neapolitan ,earthquake of #aheg1 an    
account of which was published in #ahfb1
 and to be presently further referred   
to4  ,hitherto the multitudinous facts1 
or supposed facts1 recorded in          
numberless accounts of ,earthquakes had 
remained almost wholly unclassified1 and
 so far as they had been discussed--in a
 very partial manner1 as incidental     
portions of geological treatises--with  

little attempt to sift the fabulous from
 the real1 or to connect the phenomena  
admitted by reference to any general    
mechanical or physical causes4 ,in #ahej
 my first ,report upon the ,facts of    
,earthquakes1 called for by the ,british
 ,association in #ahdg1 was read and    
published in the ,reports of that body  
for that year4 ,in this1 for the first  
time1 the many recorded phenomena of    
,earthquakes are classified1 and the    
important division of the phenomena into
 primary and secondary effects of the   
shock was established4 ,several facts or
 phenomena1 previously held as          
marvellous or inexplicable1 were either1
 on sufficient grounds1 rejected1 or    
were1 for the first time1 shown         
susceptible of explanation4 ,amongst the
 more noticeable results were the       
pointing out that fissures and fractures
 of rock or of incoherent formations    
were but secondary effects1 and1 in the 
latter1 were1 in fact1 generally of the 
nature of inceptive landslips4 ,this    

last was not accepted1 ,i believe1 by   
geologists at the time2 but the         
correctness of the views then propounded
 as to earth fissures--the nature of the
 spouting from them of water or mud--the
 appearances taken for smoke issuing    
from them1 etc4--have since been fully  
confirmed1 first1 by my own observations
 upon the effects of the ,great         
,neapolitan ,earthquake of #aheg1 and   
more lately by those of ,dr4 ,oldham    
upon the ,earthquake of ,cachar         
7,india71 where he was enabled to       
observe fissures of immense magnitude1  
the nature of the production of which he
 has well described and explained in the
 ,proceedings1 ,geological ,society1    
,london1 #ahgb4  ,the relations between 
meteorological phenomena proper and     
,earthquakes have always been a subject 
of popular belief and superstition4     
,this was here carefully discussed1 and 
with the result of disproving any       
connection1 or1 if any1 but of an       
indirect nature4 ,i also1 to some       

extent1 towards the end of this ,report1
 discussed the question of the possible 
nature of the impulse itself which      
originates the shock2 ,i showed that it 
must be of the nature of a blow1 and    
ventured to offer conjecturally five    
possible causes of the impulse3         
#a4 ,sudden fractures of rock1 resulting
 from the steady and slow      increase 
of elevatory pressure4       #b4 ,sudden
 evolution 7under special conditions7 of
 steam4       #c4 ,sudden condensation  
of steam1 also under special conditions4
       #d4 ,sudden dislocations in the  
rocky crust of the earth1 through       
pressure acting in any direction4       
#e4 ,occasionally through the recoil due
 to explosive effects at      volcanic  
foci 7p4 #gi-hj74  ,the first and last  
of these ,i am1 through subsequent      
light1 disposed now to withdraw or      
greatly to modify4  ,the first1 the     
supposed snap and jar1 occasioned by the
 sudden and violent rupture of solid    
rock masses1 to which ,mr4 ,scrope1 in  

his very admirable work on ,volcanoes1  
is disposed to refer the impulse of     
earthquake shocks 7,scrope1 #bnd edit41 
p4 #bid71 ,i believe may be proved on   
acknowledged physical principles--when  
applied to the known elasticities and   
extensibilities of rocks1 and keeping in
 view the small thicknesses fractured at
 the same instant--to be capable of only
 the most insignificant impulsive       
effects2 and if we also take into       
consideration that strata1 if so        
fractured1 are necessarily not free1 but
 surrounded by others above and below1  
any such impulsive effect emanating from
 fracture may be held as non-existent or
 impossible4 ,in the statement of his   
views which follows1 and in objecting to
 my second and third possible causes 7p4
 #bie-bif1 headed ,objections to        
,mallet's ,theory71 ,mr4 ,scrope appears
 to me to have fallen into the error of 
assuming that the nature of the impulse1
 or the cause producing it1 forms any   
part of my theory of earthquake         

movement1 or in anywise affects it4 ,i  
carefully guarded against this in the   
original ,paper 7,transactions1 ,royal  
,irish ,academy1 ,vol4 ,,xxi41 p4 #fj1  
and again1 p4 #ig71 when ,i stated it is
 quite immaterial to the truth of my    
theory of earthquake motion what view be
 adopted1 or what mechanism be assigned1
 to account for the original impulse4   
,as regards the fifth conjecture        
suggested by me1 ,i am now1 with better 
knowledge and larger observation of     
volcanic phenomena1 not prepared to     
admit any single explosion at volcanic  
vents of a magnitude sufficient to      
produce by its recoil an earthquake wave
 of any importance1 or extending to any 
great distance in the earth's crust4    
,the rock of #bjj tons weight1 said to  
have been projected nine miles from the 
crater of ,cotopaxi1 which ,i quoted    
from ,humboldt as an example1,e ,i      
believe to be as purely mythical as the 
rock 7bloc rejett7 of perhaps one-sixth 
of that weight which1 previous to the   

late eruption1 lay in the middle of the 
,atria dell ,cavallo1 and which it was  
roundly affirmed had been blown out of  
the crater1 but which in reality had at 
some time rolled down from near the top 
of the cone1 after having been dislodged
 from some part of the upper lip of the 
crater walls1 where1 as its wonderful   
hardness and texture and its enamel-like
 surface showed1 it had been roasted for
 years probably4  ,nor do ,i believe in 
the sudden blowing away of one-half the 
crater and cone of ,vesuvius1 or of any 
other volcano1 at one effort1 however   
affirmed4  ,nothing more than conjecture
 as to the nature of the impulse        
producing great or small ,earthquakes   
can1 ,i believe1 as yet be produced4    
,that there is some one master mechanism
 productive of most of the impulses of  
great shocks is highly probable1 but    
that more causes than one may produce   
these impulses1 and that the causes     
operative in small and long repeated    
shocks1 like those of ,visp-,comrie and 

,east ,haddam1 differ much from those   
producing great ,earthquakes1 is almost 
certain4  ,we shall be better prepared  
to assign all of these when we have     
admitted a true theory of volcanic      
action1 and so are better able to see   
the intimate relations in mechanism     
between seismic and volcanic actions4   
,it is not difficult meanwhile to assign
 the very probable mechanism of those   
comparatively petty repercussions which 
are experienced in close proximity to   
volcanic vents when in eruption1 and    
which1 though certainly seismic in their
 nature1 and powerful enough1 as upon   
the flanks of ,etna1 to crack and       
fissure well-built church-towers1 can   
scarcely be termed ,earthquakes4  ,in my
 ,first ,report ,i stated that almost   
nothing was known then of the           
distribution of recorded ,earthquakes in
 time or in space over our globe's      
surface1 and ,i proposed the formation  
and discussion of a complete catalogue  
of all recorded ,earthquakes1 with this 

in view4  ,this was approved by the     
,council of the ,british ,association   
and at once undertaken by me1 with the  
zealous and efficient co-operation of my
 eldest son1 ,dr4 ,j4 ,w4 ,mallet4      
,nearly the whole of the ,second        
,british ,association ,report1 of #ahea1
 is occupied with the account of the    
experiments as to the transit rate of   
artificially made shocks in sand and    
granite1 as already referred to4  ,the  
,third ,report1 of #aheb-ahed1 contains 
the whole of this1 ,the ,earthquake     
,catalogue of the ,british ,association 
7of which1 through the liberality of    
that body1 more than one hundred copies 
were distributed freely71 in which are  
given1 in columnar form1 the following  
particulars1 from the earliest known    
dates to the end of #ahdb3       #a4    
,the date and time of day1 as nearly as 
recorded4       #b4 ,the locality or    
place of occurrence4       #c4 ,the     
direction1 duration1 and number of      
shocks so far      recorded4       #d4  

,phenomena connected with the sea--great
 sea-waves1 tides1      etc4       #e4  
,phenomena connected with the           
land--meteorological phenomena          
preceding and succeeding4 ,secondary    
phenomena--all minor or      remarkable 
phenomena recorded4       #f4 ,the      
authority for the record4  ,though most 
materially assisted by the previous     
labours and partial catalogues of ,von  
,hoff1 ,cotte1 ,hoffman1 ,merrian1 and1 
above all1 of ,perrey1 the preparation  
of this catalogue--which demanded visits
 to the chief libraries of ,europe1 and 
the collating of some thousands of      
authors in various languages and of all 
time--was a work of great and sustained 
labour1 which1 except for my dear son's 
help1 ,i should never have found time   
and power to complete4 ,professor       
,perrey1 formerly of the ,facult des    
,sciences of ,dijon1 now en retrait1 who
 has devoted a long and useful life to  
assiduous labours in connection with    
,seismology1 was our great ally2 and his

 catalogues are so large and complete   
for most known parts of the world after 
#ahdb1 that we were able to arrest our  
own catalogue at that date1 and take ,m4
 ,perrey's as their continuation up to  
#ahej4  ,the whole ,british ,association
 ,catalogue thus embraces the long      
historic period of from #afjf ,b4,c4 of 
vulgar chronology1 when the first known 
,earthquake is recorded1 to ,a4,d4      
#ahej2 and the base of induction which  
it presents as to the facts recorded    
extends to between #f1jjj and #g1jjj    
separate ,earthquakes4 ,my ,fourth      
,report 7,reports1 ,british             
,association1 #aheh17 is occupied       
principally with the discussion of this 
great catalogue1 and with that of       
several special catalogues produced by  
other authors with limited areas or     
objects4  ,the discussion of ,m4        
,perrey's local catalogues with those of
 others1 in reference to a supposed     
prevalent apparent horizontal direction 
of shock in certain regions--as to      

distribution1 as to season1 months1 time
 of day or night1 relation to state of  
tide--the bearings of the views of      
,zantedeschi and others as to the       
probable existence of a terrane         
tide--the supposed relations of the     
occurrence of ,earthquakes upon the age 
of the moon1 as deduced by ,perrey1     
viz43 that #ast1 ,earthquakes occur most
 frequently at the syzygies2 #bnd1 that 
their frequency increases at the perigee
 and diminishes at the apogee2 #crd1    
that they are more frequent when the    
moon is on the meridian than when she is
 #ij away from it--and the views of     
several authorities as to the           
distribution of ,earthquakes in time and
 in space--occupy the first #df pages of
 this ,report4  ,it then proceeds to    
discuss the distribution in time and in 
space as deduced from the full base of  
the great catalogue4  ,the results as to
 time are reduced to curves1 and those  
as to space 7or distribution over our   
globe's surface7 to the great seismic   

map 7,mercator's projection71 upon which
 and in accordance with certain         
principles and conventional laws1 which 
admit of the indication of both         
intensity and frequency1 all recorded   
,earthquakes have been so laid down as  
to present a real indication of the     
distribution of seismic energy for the  
whole historic period and all over the  
world4  ,the original of this map1 which
 also shows the ,volcano 7size1 about #g
 feet by #e feet71 remains for reference
 in the custody of the ,royal ,society4 
,a reduced copy was published with the  
,report1 and to a still more reduced    
scale has been reproduced in other      
places4 ,it is impossible here to do    
more than refer to a few of the more    
salient points4  ,as regards            
distribution in time1 durational seismic
 energy may be considered as probably   
constant during historic time1 though it
 is probably a decaying energy viewed in
 reference to much longer periods4 ,it  
does not appear of the nature of a      

distinctly periodic force4       #a4    
,whilst the minimum paroxysmal interval 
may be a year or two1      the average  
interval is from five to ten years of   
comparative      repose4       #b4 ,the 
shorter intervals are in connection with
 periods of      fewer ,earthquakes1 not
 always with those of least intensity1  
but usually so4       #c4 ,the          
alternations of paroxysm and of repose  
appear to follow      no absolute law   
deducible from these causes4       #d4  
,two marked periods of extreme paroxysm 
are observable in      each century 7for
 the last three centuries71 one greater 
than      the other--that of greatest   
number and intensity occurring          
about the middle of each century1 and   
the other towards the end      of each4 
,as respects season1 there appear       
distinct indications of a maximum about 
the winter solstice1 and equally so of a
 minimum rather before the autumnal     
equinox4 ,it is not improbable that     
there is a remote relation between      

,earthquakes and the annual march of    
barometric pressure4  ,we may expect1 at
 present1 one great ,earthquake about   
every eight months1 and were we         
possessed of a sufficient report from   
all parts of our globe1 we should       
probably find scarcely a day pass       
without a very sensible ,earthquake     
occurring somewhere1 whilst1 as regards 
still smaller tremors1 it might almost  
be said that our globe1 as a whole1 is  
scarcely ever free from them4  ,as      
respects the distribution of seismic    
energy in space of our earth's surface1 
it is that of bands of variable and of  
great breadth1 with sensible seismic    
influence extending to from #e to #ae   
transversely1 which very generally      
follow3       #a4 ,the lines of elevated
 tracts which mark and divide the great 
oceanic or terra-oceanic basins 7or     
saucers1 as ,i have called      them1   
from their shallowness in relation to   
surface1 in this      discussion7 of the
 earth's surface4       #b4 ,and in so  

far as these are frequently the lines of
 mountain      chains1 and these latter 
those of volcanic vents1 so the         
seismic bands are found to follow these 
likewise4 ,isolated      ,volcanoes are 
found in these bands also4       #c4    
,while sensible seismic influence is    
generally limited to      the average   
width of the band1 paroxysmal efforts   
are      occasionally propagated to     
great distances transversely beyond     
that4       #d4 ,the sensible width of  
the band depends upon the energy        
developed at each point of the length1  
and upon the accidental      geologic   
and topographic conditions along the    
same4       #e4 ,seismic energy may     
become sensible at any point of the     
earth's surface1 its efforts being1     
however1 greater and more      frequent 
as the great lines of elevation and of  
volcanic      activity are approached2  
yet not in the inverse ratio of         
distance1 for many of the most          
frequently and terribly shaken          

regions of the earth1 as the east shore 
of the ,adriatic1 ,syria1      ,asia    
,minor1 ,northern ,india1 etc41 are at  
great distances from      active        
,volcanoes4       #f4 ,the surfaces of  
minimum or of no known disturbance are  
the      central areas of great oceanic 
or of terra-oceanic basins or           
saucers1 and the greater islands        
existing in shallow seas4  ,space       
obliges me to pass unnoticed here many  
minor but not unimportant deductions4   
,the discussions as to distribution in  
time and space occupy seventy-two pages 
of this fourth and last ,report1 the    
remainder of which 7thirty-one pages7   
embraces the description and            
mathematical discussion as to           
seismometers1 to which ,i may refer1 as 
comprising the most complete account of 
these instruments that has1 ,i believe1 
been anywhere given4  ,the appendix to  
the ,report comprises the entire        
bibliography of ,earthquakes collected  
during those researches1 and a          

concluding chapter on desiderata1 and   
inquiries as to ill-understood phenomena
 supposed to be connected with          
,earthquakes4         99       99       
99       99       99  ,in #ahdi-ej1 ,i  
was honoured by the request to draw up  
the article ,earthquake ,phenomena1     
which has appeared in the first and     
subsequent editions of the ,admiralty   
,manual of ,scientific ,inquiry4        
,originally the subject was intended to 
have formed part of the article on      
,geology1 entrusted to ,mr4 ,darwin1 who
 consulted me upon the subject2 and upon
 my representing how much ,earthquakes  
had1 within a short time1 become matter 
for the mathematician and physicist1 he1
 with a singleness of eye to science    
which it is but just to place on record1
 took the necessary steps with the      
,admiralty authorities that ,earthquakes
 should form a separate article1 and    
advised its being placed1 as it was1 in 
my hands4 ,to record this will1 ,i      
believe1 be sufficient justification for

 my reference to this article1 in which 
a good deal of information as to        
,seismometry is to be found4         99 
99       99       99       99  ,by      
recurring to ,mr4 ,hopkins's ,report on 
,earthquake ,theory1 before remarked    
upon 7,report of ,british ,association1 
#ahdg71 it will be seen that the        
solutions of the problems which he there
 gives for finding the depth of focus of
 shock are founded upon the velocity of 
propagation of the wave in the interior 
of the mass1 the apparent horizontal    
velocity and the horizontal direction of
 propagation at any proposed point being
 known 7p4 #hb74  ,by this it appears   
plainly that at that time ,mr4 ,hopkins 
supposed that it was the velocity of    
translation of the wave of shock that   
did the mischief1 and not the velocity  
of the wave particle1 or wave itself4   
,and1 further1 that the former might be 
obtained by reference simply to the     
modulus of elasticity of the rock of any
 given formation1 as1 indeed1 was my own

 earliest view when ,i produced my      
,dynamics of ,earthquake in #ahdf4 ,from
 the remarks already made as to the vast
 difference between the actual transit  
velocity in more or less discontinuous  
rocks--such as they occur in ,nature--it
 will be equally obvious that ,mr4      
,hopkins's methods1 as above mentioned1 
are impracticable1 even were there no   
confusion between the velocity of       
translation of the wave and that of the 
wave particle or wave itself4  ,this    
applies also to the demonstration and   
diagram 7taken from ,hopkins7 given by  
,professor ,phillips 7,vesuvius1 pp4    
#beh-bei74  ,in ,december1 #aheg1       
occurred the great ,neapolitan          
,earthquake1 which desolated a large    
portion of that kingdom2 and an         
opportunity then arose for practically  
applying to the problems of finding the 
directions of earthquake shock at a     
given point through which it has passed1
 and ultimately the position and depth  
of focus1 other methods1 which ,i had   

seen1 from soon after the date of       
publication of my original ,paper       
7#ahdf71 were easily practicable1 and   
the details of which ,i had gradually   
matured4  ,bearing in mind that1 in the 
case of the normal vibration in any     
elastic solid of indefinite dimensions1 
the direction of motion in space of the 
wave particle coincides in the first    
semiphase of the wave1 and at the       
instant of its maximum velocity with the
 right line joining the particle and the
 focus or centre of disturbance1 it     
follows that1 in the case of            
earthquakes1 the normal vibration of the
 wave of shock is always in a vertical  
plane passing through the focus and any 
point on the earth's surface through    
which the shock passes 7assuming for the
 present no disturbing causes after the 
impulse has been given71 and that at    
such a point the movement of the wave   
particle in the first semiphase of the  
wave is in the same direction or sense  
as that of translation2 and at the      

moment of maximum velocity the direction
 in space of the motion of the wave     
particle is that of the right line      
joining the point through which the wave
 has passed with the focus or centre of 
impulse4  ,if1 therefore1 we can        
determine the direction of motion of the
 wave particle in the first semiphase1  
and its maximum velocity1 we can obtain1
 from any selected point1 a line 7that  
of emergence of the shock7 somewhere in 
which1 if prolonged beneath the earth1  
the focus must have been2 and if we can 
obtain like results for two or more     
selected points1 we decide the position 
and the depth of the focus1 which must  
be in the intersection of the several   
lines of direction of the wave particle 
motion at each point1 when prolonged    
downwards4  ,now1 as ,i have said1 it is
 the vibration of the wave itself1 i4e41
 the motion of the wave particle that   
does the mischief--not the transit of   
the wave from place to place on the     
surface2 just as in the analogous 7but  

not similar7 case of a tidal wave of    
translation running up an estuary and   
passing a ship anchored there1 it is not
 the transit up the channel1 but the    
wave form itself--i4e41 the motion of   
the wave particles--that lifts the ship1
 sends her a little way higher up       
channel1 drops her to her former level1 
and sends her down channel again to the 
spot she lay in just before the arrival 
of the wave4  ,everything1 therefore1   
that has been permanently disturbed by  
an earthquake shock has been thus moved 
in the direction and with the maximum   
velocity impressed upon it by the wave  
particle in the first semiphase of the  
wave2 and thus almost everything that   
has been so disturbed may1 by the       
application of established dynamical    
principles1 be made to give us more or  
less information as to the velocity of  
the wave particle 7or as we1 for        
shortness1 say1 the velocity of shock71 
the direction of its normal vibration1  
and the position and depth beneath the  

earth's surface1 from which came the    
generating impulse4 ,we thus arrive at  
these as simply and as surely as we can 
infer from the position taken by a      
billiard ball1 on which certain forces  
are known to have acted1 the forces     
themselves and their direction2 or1 from
 a broken beam1 the pressure or the blow
 which fractured it4  ,it is obvious1   
then1 that nearly every object          
disturbed1 dislocated1 fractured or     
overthrown by an earthquake shock is a  
sort of natural seismometer1 and the    
best and surest of all seismometers1 if 
we only make a judicious choice of the  
objects which being found after such a  
shock1 we shall employ for our purpose4 
,this was the principle which ,i        
proposed to the ,royal ,society at once 
to apply to the effects of the then     
quite recent great ,neapolitan          
,earthquake of #aheg1 and which1 through
 the liberality and aid of that body1 ,i
 was enabled to employ with the result  
,i had pretty confidently anticipated1  

namely1 the ascertainment of the        
approximate depth of the focus4  ,every 
shock-disturbed object in an            
earthquake-shaken country is capable of 
giving some information as to the shock 
that acted upon it2 but it needs a      
careful choice1 and some mechanical     
,greek3 nous1 to select proper and the  
best objects1 so as to avoid the        
needless perplexity of disturbing forces
 not proper to the shock1 or other      
complications4  ,when properly chosen1  
these natural seismometers1 or evidences
 fitted for observation after the shock1
 are of two great classes1 by which the 
conditions of the earthquake motion are 
discoverable3       #a4 ,fractures or   
dislocations 7chiefly in the masonry of 
buildings71 which afford two principal  
sources and sorts of      information1  
namely3       a4 ,from the observed     
directions of fractures or fissures1    
by which the wave path1 and frequently  
the angle of      emergence1 may be     
immediately inferred4       b4          

,information from the preceding1 united 
with known      conditions as to the    
strength of materials to resist         
fracture1 by which the velocity of the  
fracturing impulse      may be          
calculated4       #b4 ,the overthrow or 
the projection1 or both1 of bodies large
 or      small1 simple or complex4 ,from
 these we are enabled to infer3       c4
 ,by direct observation1 the direction  
in azimuth of the      wave path4       
d4 ,by measurements of the horizontal   
and vertical distances      of overthrow
 or of projection1 to infer either the  
velocity      of projection1 or angle of
 emergence4  ,fractures by shock present
 their planes always nearly in          
directions transverse to the wave path4 
,projections or overthrow take place    
7unless secondarily disturbed7 in the   
line of the wave path1 or in the        
vertical plane passing through it3 but  
the direction of fall or overthrow may  
be either in the same direction as the  
wave transit 7i4e41 as the motion of the

 wave particle in the first semiphase71 
or contrary to it4  ,it is thus obvious 
that the principal phenomena presented  
by the effects of earthquake shock upon 
the objects usually occurring upon the  
surface of the inhabited parts of the   
earth1 resolve themselves into problems 
of three orders1 and are all amenable to
 mechanical treatment1 viz43       #a4  
,problems relating to the direction and 
amount of velocity      producing       
fracture or fissures4       #b4         
,problems relating to the single or     
multiplied oscillations      of bodies1 
considered as compound pendulums4       
#c4 ,problems referable to the theory of
 projectiles4  ,these three may combine 
in several cases1 and on the part of the
 observer must combine with             
measurements1 angular and linear1 and   
with geodetic operations to be conducted
 in the shaken country4  ,the methods of
 application in detail are described    
fully1 as well as their actual          
application and results1 in my work     

published in #ahfb 7#b vols471 entitled 
,the ,first ,principles of              
,observational ,seismology1 as developed
 in the ,report to the ,royal ,society  
of ,london of the ,expedition made by   
,command of the ,society into the       
,interior of the ,kingdom of ,naples1 to
 investigate the ,circumstances of the  
,great ,earthquake of ,december1 #aheg1 
to the many illustrations of which the  
pecuniary grant1 in aid1 of #cjj was    
most liberally made to the publishers   
7,messrs4 ,chapman and ,hall7 by the    
,society4  ,it is not my intention here1
 nor would space allow1 of my going into
 the details of observation1 nor of the 
deductions and conclusions ,i have      
recorded in those volumes4 ,i have      
referred to their contents as marking   
the advent of a new method4 ,i have     
ventured to call it a new organon in the
 investigation of ,earthquakes1 and1    
through them1 of the deep interior of   
our earth2 and will only add that the   
method1 on this its very first trial1   

proved fertile and successful4 ,the     
depth of focus for this shock of        
,december1 #aheg1 was about seven to    
eight geographical miles below sea      
level1 roughly stated4 ,it gives me     
great pleasure to add that my friend1   
,dr4 ,oldham1 ,director-,general of the 
,geological ,survey of ,india1 has since
 applied these same methods to the      
phenomena of the great ,cachar          
,earthquake of the #ajth ,january1      
#ahfi1 and with success4 ,the pressure  
of official duties has1 he informs me1  
as yet prevented his fully working out  
his results1 but they appear so far to  
indicate1 as we should expect1 a depth  
of focus or origin considerably greater 
than in the ,european case of #aheg4    
,some account of ,dr4 ,oldham's results 
were this year communicated to the      
,geological ,society of ,london through 
myself1 they are of great interest and  
importance4  ,such1 briefly and         
imperfectly sketched1 is the existing   
state of ,seismology4 ,as a branch of   

exact science it is1 as it were1 an     
affair of yesterday4 ,it is with        
reluctance that ,i have been compelled1 
in this review1 to refer to my own work 
so prominently4 ,the harvest has been   
and still is plenteous1 but in this     
field of intellectual work the labourers
 are few4 ,this must continue to be so  
as long as ,geology shall continue to be
 viewed in public estimation 7in        
,england at least7 as a fashionable toy1
 that everyone who has been to school is
 supposed capable of handling2 and until
 all who profess to be geologists shall 
have learnt that1 to make sound         
progress1 they must first become        
mathematicians1 physicists and chemists4
  ,it is to the general imperfect       
knowledge of these sciences amongst     
geologists that speculative errors show 
such vitality1 and that ,geology makes  
such poor progress towards becoming the 
interpretation of the world as a machine
 7,erdkunde74  ,it is for the same      
reason that ,seismology and ,vulcanology

 make little progress2 the first cannot 
be pursued beyond its present           
boundaries1 nor can even its present    
position be understood or explained by  
anyone unfamiliar with the laws of wave 
motion1 of all classes of waves2 and it 
would be easy to show1 by quoting from  
various ,british or foreign text-books  
on ,geology1 how extremely imperfect is 
the grasp of some of the authors upon   
the subject of earthquake-wave motion1  
even such as they admit and endeavour to
 explain and apply3 in fact1 many       
geologists appear never to have framed  
to themselves any clear idea of what is 
a wave of any sort1 liquid or elastic4  
,the general silence as to seismic      
theory of ,french geological writers is 
remarkable1 to whatever cause           
attributable4 ,it has been said that    
,french philosophers show themselves    
little disposed to acknowledge or to    
follow the lead of their foreign        
compeers in any branch of science4 ,if  
this be true1 or in so far as it may be 

so1 it is unworthy of ,french science1  
which has such boundless claims upon our
 homage4 ,i am disposed to attribute the
 fact in this case to other             
circumstances2 and1 amongst these1 to   
the small extent to which our language  
is known amongst ,french scientific men4
  ,germany has shown more desire to     
cultivate this branch of science4       
,although1 as yet1 the distinct         
enunciation of its fundamental          
principles has but sparsely found its   
way into her text-books1 several able   
monographs1 such as those of ,schmidt   
and of ,httinger1 prove how completely  
some of her philosophers have mastered  
and how well applied them4 ,the men of  
science of ,northern ,italy1 amongst    
whom so many glorious names are to be   
found on the roll of discovery1 have    
shown themselves quite alive to the     
importance of ,seismology2 and ,i know  
of no more clear1 exact and popular     
exposition of its principles and        
application1 and of its cosmical        

relations1 than is to be found in a     
small volume by ,professor ,gerolamo    
,boccardo1 published at ,genoa in #ahfi1
 entitled ,sismopirologia ,terremoti1   
,vulcani e lente oscillazione del suolo1
 saggio di una teoria di ,geographia    
,fisica4  ,my object1 so far1 has been  
to mark the progress of ascertained     
theoretic notions as to ,seismology4 ,i 
have1 therefore1 passed without notice  
many speculative monographs1 and the    
treatment upon ,earthquakes1 whether    
speculative or historical1 and however  
able1 that constitutes a prominent      
feature of nearly all systematic works  
on ,geology4  ,that which may be at     
present viewed as achieved and certainly
 ascertained in theoretic ,seismology is
 the clear conception of the nature of  
earthquake motion2 the relations to it  
of great sea or other water wave        
commotions2 the relations to it of sound
 waves--as to which1 however1 more      
remains to be known2 and the relations  
of all these to secondary effects1      

tending in various ways to modify more  
or less the topographic and other       
conditions of the land or sea bottom4   
,and in descriptive ,seismology the     
present distribution of the earthquake  
bands or regions of greatest seismic    
prevalence and activity are tolerably   
ascertained1 and their connection with  
volcanic lines and those of elevation   
rendered more evident4 ,viewed alone1   
nothing can yet be said to be absolutely
 ascertained as to the immediately      
antecedent cause or causes of the       
impulse4 ,the function of ,earthquake1  
as part of the cosmical machine1 has    
become more clear1 as the distinctive   
boundaries between ,earthquake and      
permanent elevation of the earth have   
been made evident2 and it has been seen 
that ,earthquake1 however               
contemporaneous occasionally with       
permanent elevation1 is not the cause1  
though it may be one of the consequences
 of the same forces which produce       
elevation2 and thus1 that an infinite   

number of ,earthquakes1 however violent1
 and acting through however prolonged a 
time1 can never act as an agent of      
permanent elevation1 unless1 indeed1 on 
that minute scale in which surface      
elevation may arise from secondary      
effects1 like that of the ,ullah ,bund4 
,much remains to be done1 and much may  
be expected even from the continuation1 
if done in a systematic and organised   
manner1 of the statistic record of      
,earthquakes in connection with those   
other branches of cosmical statistics1  
,climatology1 ,meteorology1 ,terrestrial
 ,magnetism1 etc41 the observation of   
which is already1 to a certain extent1  
organised over a large portion of the   
globe4  ,and now let us look back for a 
moment to ask1 ,how1 by what mental path
 of discovery1 have we arrived at what  
we have passed in review8  ,the facts of
 ,earthquakes have been before men for  
unknown ages open secrets1 as ,nature's 
facts have been well called2 but eyes   
had they and saw not4 ,facts viewed     

through the haze of superstition1 or of 
foregone notions of what ,nature ought  
to do1 cease to be facts4 ,when1 after  
the great ,calabrian ,earthquake of     
#aghc1 the ,royal ,academy of ,naples   
sent forth its commission of its learned
 members to examine into the effects1   
they had spread around them in sad      
profusion all that was necessary to have
 enabled them to arrive at a true notion
 of the nature of the shock1 and thence 
a sound explanation of the varied and   
great secondary effects they witnessed1 
and of which they have left us the      
records in their ,report1 and the       
engravings illustrative of it4 ,but we  
look in vain for any light2 the things  
seen1 often with distortion or          
exaggeration1 are heaped together as in 
the phantasmagoria of a wild and        
terrible dream1 from which neither order
 nor conclusion follow4  ,why was this8 
,why were these eminent savants no more 
successful in explaining what they saw  
than the ignorant peasants they found in

 the ,calabrian mountains8  ,because    
physical science itself was not         
sufficiently advanced1 no doubt2 but    
also because they had no notion of      
applying such science as they had1 to   
the very central point itself of the    
main problem before them1 freed from all
 possible adventitious conditions1 and  
so1 as it were1 attacking it in the     
rear4 ,how different might have been the
 result of their labours1 had they begun
 by asking themselves1 ,what is an      
earthquake8 ,can we not try to find out 
what it is by observing and measuring   
what it has done8 ,we see the converse  
mode of dealing with ,nature in         
,torricelli4 ,nature abhors a vacuum1   
was told him1 as the wisdom of his day4 
,possibly3 but her abhorrence is        
limited1 for ,i find it is measured by  
the pressure of a column of water of    
thirty-four feet in height4 ,we need not
 pursue the story with ,pascal1 up to   
the top of the ,puy de ,dme4  ,this     
lesson is instructive generally to all  

investigators1 and particularly here2   
for ,vulcanology1 to which we are about 
now to turn1 has occupied until almost  
to-day much the same position that      
,seismology did in those of the         
,neapolitan ,commissioners4  ,whole     
libraries have been written with respect
 to it dealing with quality1 but measure
 and quantity remain to be applied to   
it4  ,to a very preponderant class in   
the civilised world no knowledge is of  
much interest or value that does not    
point to what is called a practical     
result1 one measurable into utility or  
coin4 ,i do not stop to remark as to the
 bad or as to certain good results of   
this tendency of mind2 but ,i may       
venture to point out to all1 that the   
exact knowledge of the nature of        
earthquake motion1 even during the short
 time that it has become known1 has not 
been barren in results absolutely       
practical and utilitarian4 ,the minute  
investigation of the destruction of     
buildings1 etc41 and the deductions that

 have been made as to the relations     
between the form1 height1 materials1    
methods of building1 combination of     
timber and of masonry1 and many other   
architectural or constructive           
conditions1 have made it certain now    
that earthquake-proof houses and other  
edifices can be constructed with        
facility1 and at no great increase1 if  
any at all1 of cost4 ,i can affirm that 
there is no physical necessity why in   
frequently and violently shaken         
countries1 such as ,southern ,italy or  
the ,oriental end generally of the      
,mediterranean1 victims should hereafter
 continue by thousands to be sacrificed 
by the fall of their ill-designed and   
badly built houses4  ,were a ,building  
,act properly framed1 put in force by   
the ,italian ,government in the         
,basilicatas and ,capitanata1 etc41 so  
that new houses or existing ones1 when  
rebuilt1 should be so in accordance with
 certain simple rules1 a not very       
distant time can be foreseen when       

,earthquakes1 passing through these rich
 and fertile but now frequently sorely  
afflicted regions1 should come and go1  
having left but little trace of ruin or 
death behind4 ,some disasters there must
 always be1 for we cannot make the      
flanks of mountains1 nor the beds of    
torrents1 etc41 always secure2 but the  
main mortality of all ,earthquakes is in
 the houses or other inhabited          
buildings4 ,make these proof1 and the   
wholesale slaughter is at an end4  ,the 
principles we have established have been
 thus practically applied in another    
direction4 ,the ,japanese ,government1  
with the keen and rapid perception of   
the powers inherent in ,european science
 which characterises now that wonderful 
people1 has commenced to illuminate its 
coasts by lighthouses constructed after 
the best ,european models4 ,but ,japan  
is greatly convulsed by earthquakes1 and
 lighthouses1 as being lofty buildings1 
are peculiarly liable to be destroyed by
 them4  ,the engineer of the ,japanese  

,government for these lights1 ,mr4      
,thomas ,stevenson1 ,c4,e4 7one of the  
engineers to the ,commissioners of      
,northern ,lights71 was instructed to   
have regard1 in the design of those     
lighthouses1 to their exposure to shock4
 ,i was consulted by ,mr4 ,stevenson as 
to the general principles to be         
observed2 and those edifices have been  
constructed so that they are presumedly 
proof against the most violent shocks   
likely to visit ,japan2 not1 perhaps1   
upon the best possible plan1 but upon   
such as is truly based upon the         
principles ,i have developed4 ,mr4      
,stevenson has published some account of
 their construction4  ,the earthquake   
regions of ,south ,america might with   
incalculable benefit apply those ideas2 
and1 indeed1 they have been1 to some    
extent1 already applied by my friend1   
,mr4 ,william ,lloyd1 ,member of the    
,institution of ,civil ,engineers1 to   
the ,new ,custom ,houses constructed    
from his designs at ,valparaiso4  ,as   

one of these utilitarian views1 and an  
important one1 it will occur to many to 
ask--,can the moment of the occurrence  
or the degree of intensity of earthquake
 shock be predicted1 or is it probable  
that at a future day we may be able to  
predict them8 ,at present1 any          
prediction1 either of the one or the    
other1 is impossible2 and those few who 
have professed themselves in possession 
of sufficient grounds for such          
prediction are deceivers or deceived4   
,nor is it likely that1 for very many   
years to come1 if ever1 science shall   
have advanced so as to render any such  
prediction possible2 but it is neither  
impossible nor improbable that the time 
shall arrive when1 within certain1      
perhaps wide1 limits as to space1       
previous time1 and instant of           
occurrence1 such forewarnings may be    
obtainable4  ,earthquakes1 like storms  
and tempests1 and nearly all changes of 
weather1 are not periodic phenomena1 nor
 yet absolutely uncertain or1 so to say1

 accidental as to recurrence4  ,they are
 quasi-periodic1 that is to say1 some of
 their conditions as to causation rest  
upon a really periodic basis1 as1 for   
example1 the recurrence of storms upon  
the periodic march of the earth1 and sun
 and moon1 etc41 and the recurrence of  
,earthquakes upon the secular cooling of
 our earth2 but the conditions in both  
are so numerous and complicated with    
particulars1 that we cannot fully       
analyse them--hence1 cannot reduce the  
phenomena to law1 and so cannot predict 
recurrence4 ,yet storms and             
tempests--which were1 along with        
pestilences and ,earthquakes1 amongst   
the natural phenomena which ,bishop     
,butler deemed in his own day impossible
 of human prediction--have already1     
through the persistent and systematised 
efforts of meteorological observers1    
become to a certain extent foreseeable2 
and medical science assures us that it  
has rendered that1 though to a much less
 degree of probability1 true of         

pestilences4  ,we may1 therefore1 give  
the utilitarian some hope1 that if he   
will help us along--who value our       
accessions of knowledge primarily upon a
 different standard to his--in our talk 
of discovery1 our posterity1 in a       
century or two hence1 may not improbably
 possess the advantage of being able1 in
 some degree1 to predict their          
,earthquakes4 ,i fear the inducement    
will go but a small way with the        
utilitarian generation1 whose bent tends
 much towards asking1 ,what has         
posterity ever done for them8  ,but     
though we cannot as yet predict the time
 when an ,earthquake may take place in  
any locality1 we can1 on mixed statistic
 and dynamic grounds1 in many cases     
state the limits of probable violence of
 the next that may recur4 ,for example1 
the three shafts of marble columns of   
the ,temple of ,serapis1 at ,pozzuoli1  
each of about #da-a_/b feet in height1  
and #d feet #aj inches in diameter at   
the base1 remain standing alone1 since  

they were uncovered1 in the year #agej4 
,now1 as we can calculate exactly what  
velocity of earthquake-wave motion would
 be required to overset these1 we are   
certain that1 during the last one       
hundred and twenty-two years1 the site  
of the ,temple1 and we may say ,naples  
and the ,phlegran fields generally1 have
 never experienced a shock as great as  
the very moderate one that would overset
 these columns4 ,a shock whose wave     
particle had a horizontal velocity of   
only about #c-a_/b feet 7,british7 per  
second would overturn these columns2    
which is only about one-fourth the      
velocity 7within the meizoseismic area7 
of the great shock of #aheg1 that       
produced wide-spread destruction in the 
,basilicatas1 and not enough to throw   
down any reasonably well-built house of 
moderate height4  ,naples1 so far as    
,earthquake is concerned1 whether coming
 from the throes of ,vesuvius or        
elsewhere1 has a pretty good chance of  
safety4 ,she may possibly 7though not   

probably7 be some day smothered in      
ashes2 but is in little danger of being 
shaken to the earth4 ,during this time  
there have been taking place1 larger    
eruptions of ,vesuvius and earthquake   
shocks from other centres1 together     
probably about the same number of times 
as the numbers of those years1 when     
those columns have been more or less    
shaken4  ,we may therefore affirm that  
the probability 7on the basis of this   
experience only7 is1 say #abj to #a1    
that the next shock1 whether derived    
from ,vesuvius1 or elsewhere1 that may  
shake ,pozzuoli1 will be one less in    
power than would be needed to overturn  
the shafts of the ,temple of ,serapis   
there4         99       99       99     
99       99  ,let us now turn to the    
second branch of our subject--viz41     
,vulcanology--upon which1 as yet1 we    
have secured less firm standing ground  
than we have seen we possess in         
,seismology1 for which reason we took   
that first into consideration4  ,it is  

the part of ,vulcanology to co-ordinate 
and explain all the phenomena of past or
 present times visible on our globe     
which are evidences of the existence and
 action1 whether local or general1 of   
temperatures within our globe greatly in
 excess of those of the surface1 and    
which reach the fusing points of various
 mineral compounds as found arriving1   
heated or fused1 at the surface4  ,the  
stratigraphic geologist sees that such  
heated or fused masses have come up from
 beneath1 throughout every epoch that he
 can trace2 but he cannot fail to       
discern more or less a change in the    
order or character of those outcomings1 
as he traces them from the lowest and   
oldest formations to those of the       
present day4 ,he sees immense           
outpourings of granitoid or porphyrytic 
rocks that have welled up and overflowed
 the oldest strata--huge dykes filling  
miles of fissures that had been         
previously opened for the reception of  
the molten matter that has filled them1 

and often passing through those masses  
of previously outpoured rock2 later he  
sees huge tables of basaltic rock poured
 forth over all4 ,one grand             
characteristic common to all            
these--commonly called plutonic         
products--being that1 whether they were 
poured forth over the surface or        
injected into cavities in other rocks1  
the movements of the fused material     
were1 on the whole1 hydrostatic and not 
explosive4  ,at the present day1        
whatever other evidences we have of high
 temperature below our globe's surface1 
that which primarily fixes the eye of   
the geologist is the ,volcano1 whose    
characteristic1 as we see it in         
activity1 is explosive4 ,but though     
there is this great characteristic      
difference between the plutonic and the 
volcanic actions and their products1 the
 two1 when looked at largely1 are seen  
so to inosculate1 that it is impossible 
not to refer them to an agency common to
 both1 however changed the modes of its 

action have been between the earliest   
epochs of which traces are presented to 
us and the present day4  ,to us little  
men1 who1 as ,herschell has well said1  
in referring to the methods of measuring
 the size of our globe1 can never see it
 all at once1 but must creep like mites 
about its surface1 the ,volcano1 in the 
stupendous grandeur of its effects1     
tends to fix itself in our minds in     
exaggerated proportions to its true     
place in the cosmic machine2 and1 in    
fact1 nearly all who have sought to     
expound its nature and mode of          
origination have occupied themselves far
 too exclusively with describing and    
theorising upon the strange and varied  
phenomena which the volcanic cone itself
 and its eruptions present1 and too     
often1 in the splendour and variety of  
these1 have very much lost sight of what
 ought to be the centre-point of all    
such studies1 namely1 to arrive at some 
sound knowledge of what is the primum   
mobile of all these wonderful efforts4  

,nor has the distinction been very      
clearly seen between the main phenomena 
presented at and about volcanic active  
mouths1 which can be employed to        
elucidate the nature of the causation at
 work far below1 and those most varied  
and curious1 and in other respects most 
pregnant and instructive phenomena1     
mechanical and chemical1 which are      
called into action in and by the ejected
 matter of the volcanic cone after its  
ejection4 ,it can help us but little or 
very indirectly1 in getting at a true   
conception of the nature and source of  
the heat itself of the ,volcano1 to     
examine1 for example1 all the curious   
circumstances that are seen in the      
movements and changes in the lava that  
has already flowed from its mouth2 but  
it would be of great importance if we   
can ascertain1 by any form of           
observation around the cone1 from what  
depth it has come1 or at what depth the 
igneous origin lies4  ,the physician1   
endeavouring to ascertain the real      

nature of small-pox or measles1 will    
scarcely make much progress who1 however
 curiously or minutely1 confines his    
attention to the pustules that he sees  
upon the skin4  ,yet the ,volcano1 or   
rather all volcanic activity as now     
operative upon our globe1 is1 as it     
were1 an experiment of ,nature's own    
perpetually going on before us1 the     
results of which1 if well chosen--that  
is1 as ,bacon says1 by keeping to the   
main and neglecting the accidents--can1 
when colligated and correctly reasoned  
upon1 in relation to our planet as a    
whole1 give us the key to the enigma of 
terrestrial ,vulcanicity in its most    
general sense1 and at every epoch of our
 world's geognostic history1 and show us
 its true place and use in the cosmical 
machine4 ,let us glance at the history  
of past speculation on this subject1    
from which so little real knowledge is  
to be derived1 and then at the salient  
facts of ,vulcanology as now seen upon  
our earth1 and finally see if we can    

connect these with other great cosmical 
conditions1 so as to arrive at a        
consistent explanation in harmony with  
all4  ,we gain nothing absolutely from  
the knowledge of the so-called ancients 
as to ,volcanoes in ,europe at least1   
where alone historic records likely to  
refer to them exist4 ,the ,volcanoes of 
,europe are few and widely scattered4   
,the ,greeks saw but little of them1 and
 the ,romans were all and at all times  
most singularly unobservant of natural  
phenomena4  ,csar never mentions the    
existence in ,france of the ,volcanoes  
of ,auvergne1 so much like those he must
 have seen in ,italy and ,sicily2 and   
,roman writers pass in silence that     
great volcanic region1 though inhabited 
by them1 and their language impressed   
upon the places1 as ,volvic             
7volcano-vicus7 seems with others to    
indicate2 and though there is some      
reason to believe that one or other of  
the ,puys was in activity within the    
first five hundred years of our epoch1  

the notices which ,humboldt and others  
have collected as from ,plato1          
,pausanius1 ,pliny1 ,ovid1 etc41 teach  
nothing4  ,whatever of mere speculation 
there may have been1 volcanic theory1 or
 what has passed for such1 there was    
none before #agjj1 when ,lmry brought   
forward a trivial experiment1 the       
acceptance of which1 even for a moment1 
as a sufficient cause for volcanic heat 
7and it retarded other or truer views   
for years71 we can now only wonder at4  
,breislak's origin1 in the burning of   
subterranean petroleum or like          
combustibles1 was scarcely less absurd  
than ,lmry's sulphur and iron filings4  
,davy1 in the plenitude of his fame1 and
 full of the intense chemical activities
 of the metals of the alkalies which he 
had just isolated1 threw a new but      
transient verisimilitude upon the       
so-called chemical theory of ,volcanoes1
 by ascribing the source of heat to the 
oxidation of those metals assumed to    
exist in vast1 unproved and unindicated 

masses in the interior of the earth4    
,but ,davy had too clear an intellect   
not to see the baseless nature of his   
own hypothesis1 which in his last work1 
the ,consolations in ,travel1 he        
formally recanted2 and it only survived 
him in the long-continued though        
unconvincing advocacy of ,dr4 ,daubeny4 
,so far1 the origin of the heat had been
 sought always1 in the crude notion of  
some sort of fuel consumed1 whether that
 were petroleum or potassium and sodium2
 but as no fuel was to be found1 nor any
 indicated by the products1 so far as   
known1 of the volcanic heat1 so what has
 been called the mechanical theory1 in a
 variety of shapes1 took its place4     
,this1 in whatever form1 takes its lava 
and other heated products of the volcano
 ready made from a universal ocean of   
liquid material1 which it supposes      
constitutes the interior or nucleus of  
our globe1 and which is only skinned    
over by a thin1 solid crust of cooled   
and consolidated rock1 which was        

variably estimated at from fourteen to  
perhaps fifty miles in thickness4 ,here 
was a boundless supply of more than     
heat1 of hot lava ready made1 the       
existence of which at these moderate    
depths the then state of knowledge of   
hypogeal temperature1 which was supposed
 to go on increasing with depth at the  
rate of about #a ,fahrenheit1 for every 
thirty or forty feet1 seemed quite to   
sustain4  ,the difficulty remained1 how 
was this fiery ocean brought to the     
surface or far above it8 ,to account for
 this two main notions prevailed1 and1  
indeed1 have not ceased to prevail4     
,some unknown elastic gases or vapour   
forced it up through fissures or rents  
pre-existent1 or produced by the tension
 of the elastic and liquid pressure     
below4  ,the form in which this view    
took most consistency1 and approaching  
most nearly to truth1 finds the elastic 
vapour in steam generated from water    
passed down through fissures from the   
sea or from the land surface4 ,but to   

this the difficulty was started1 that   
fissures that could let down water would
 pass up steam4 ,the objection1 when all
 the conditions are adequately          
considered1 has really no weight2 and it
 has been completely disposed of1 since 
within a few years it has been proved   
that capillary infiltration goes on in  
all porous rocks to enormous depths1 and
 that the capillary passages in such    
media1 though giving free vent to       
water--and the more as the water is     
warmer--are1 when once filled with      
liquid1 proof against the return through
 them of gases or vapours4 ,so that the 
deeply seated walls of the ducts leading
 to the crater1 if of such material1 may
 be red hot and yet continue to pass    
water from every pore 7like the walls of
 a well in chalk71 which is flushed off 
into steam that cannot return by the way
 the water came down1 and must reach the
 surface again1 if at all1 by the duct  
and crater1 overcoming in its way       
whatever obstructions they may be filled

 with4  ,and this remarkable property of
 capillarity sufficiently shows how the 
lava--fused below or even at or above   
the level of infiltration--may become   
interpenetrated throughout its mass by  
steam bubbles1 as it usually but not    
invariably is found to be4  ,nor is it  
difficult to see such a mechanism       
between volcanic ducts and fissures     
conveying down water1 as large and open 
pipes1 for a large part of their depth1 
as shall bring down water to foci of    
volcanic heat1 without the power of the 
water flowing back except as steam and  
through the crater4  ,indeed1 the facts 
known as to geysers1 and those of       
half-drowned-out ,volcanoes such as     
,stromboli--whose action is intermittent
 just as much as that of a geyser--show 
that this is not merely probable4 ,there
 is1 therefore1 no need for the         
hypothesis of those who have supposed   
all the huge volumes of steam blown off 
from ,volcanoes in eruption to come from
 vesicular water pre-existent in the    

minute cavities of crystalline or other 
rocks before their fusion into lava3 a  
fact not proved for many classes of     
rock1 and for none in sufficient        
quantity to account for the vast volume 
of steam required and for the           
irregularity of its issue4  ,it is      
rather to anticipate1 but ,i may state  
at once that1 so far as the admission of
 superficial waters to the interior1 and
 to any depth to which fissures or      
dislocation can extend1 ,i believe no   
valid physical or mechanical            
difficulties exist1 taking into account 
all the conditions that may come into   
play together4  ,another set of views   
has been suggested and supported by     
various writers1 which proposes to      
account for the rise of lava on purely  
hydrostatic principles4 ,the solid      
crust1 fractured into isolated fragments
 by tensions due to its own contraction1
 is supposed to sink into the sea of    
lava on which it floats2 and much       
ingenuity has been expended in imagining

 the mechanism by which1 in places1 the 
liquid matter is supposed to rise above 
the surface of the crust4  ,i have no   
space for discussing these views further
 than to assert that1 in the existing   
state of our globe1 and even admitting a
 solid crust of only #fj1jjj metres     
thick1 dislocation of the crust by      
tension is not possible4 ,the solid     
crust of our globe1 as ,i hope we shall 
see further on1 is not in a state of    
tension1 and has not been so since it   
was extremely thin1 a mere pellicle as  
compared with the liquid nucleus1 but   
is1 on the contrary1 in a state of      
tangential compression4  ,however       
tenable1 in other respects1 may be the  
volcanic theory which rests upon the    
assumption of a very thin crust and a   
universal ocean of fused rock beneath1  
it fails wholly to explain many of the  
most important circumstances observable 
as to the distribution and movements of 
existing ,volcanoes on our globe4  ,it  
affords no adequate explanation of the  

configuration of the lines of           
,volcanoes1 nor of their occurrence in  
the ocean bed1 nor of their existence in
 high latitudes1 near the ,poles1 where1
 no matter how or at what rate our globe
 cooled from liquidity1 the crust must  
be thickest2 nor of the independence of 
eruptive action of closely adjacent     
volcanic vents2 nor of the              
non-periodicity1 the sudden awakening-up
 to activity1 the as sudden exhaustion1 
the long repose1 the gradual decay of   
action at particular vents1 and of much 
more that might be stated and sustained 
as difficulties left by that theory     
unexplained1 or that are of a nature    
even opposed to it4  ,the researches of 
the last few years have1 however1 as it 
appears to me1 rendered any theory that 
demands as its postulates a very thin   
crust1 and a universal liquid nucleus   
beneath it1 absolutely untenable4       
,without attaching any importance to the
 arguments of ,mr4 ,hopkins1 based upon 
precession and nutation1 it appears to  

me1 on various other grounds1 some of   
which have been urged by ,sir ,william  
,thompson1 that the earth's solid crust 
is not a thin one1 at least not thin    
enough to render it conceivable that    
water can ever gain admission to a fluid
 nucleus1 if any such still exist1      
situated at so great a depth2 and       
without such access we can have no      
,volcano4 ,it is not necessary to go to 
the extent of a crust of #hjj or #a1jjj 
miles thick3 with one of half the minor 
thickness1 ,i believe it may be proved1 
on various grounds1 hydraulic amongst   
others1 that neither water could reach  
the nucleus1 nor the liquid matter of   
the nucleus reach the surface4 ,mr4     
,hopkins having proved to his own       
satisfaction an enormous thickness for  
the crust1 and seeing clearly the       
difficulties that this involved to the  
generally accepted volcanic theory1 and 
having no other to substitute for it1   
fell back upon that most vague and weak 
notion of the existence of isolated     

lakes of liquid rock1 existing at       
comparatively small depths beneath the  
earth's surface within the solid and    
relatively cold crust1 each supplying   
its own ,volcano1 or more than one1 with
 ready-made lava4 ,what is to produce   
these lakes of fused matter in the midst
 of similar solidified matter8 what is  
perpetually to maintain their fluidity  
in the midst of solid matter continually
 cooling8 what has given them their     
local position8 why near or less near   
the surface8 what should have arranged  
them in directions stretching in some   
cases nearly from ,pole to ,pole8       
,surely this creation of imaginary      
lakes1 merely because it happens to fit 
the vacant chink that seems needed to   
wedge up a falling theory1 is an        
instance of that abuse of hypothesis    
against which ,newton so vehemently     
declaims--,hypotheses non fingo4        
,hypothesis1 to be a philosophic        
scaffolding to knowledge1 must1 as      
,whewell has said1 be close to the      

facts1 and not merely connected with    
them by arbitrary and untried facts4    
,yet this appears accepted by ,lyell    
7#ajth edition1 ,vol4 ,,ii41 p4 #bbg1   
and elsewhere72 by ,phillips 7,vesuvius1
 pp4 #cca1 #ccb72 by ,scrope1 if1 as ,i 
hope1 ,i mistake him not 7,volcanoes1   
pp4 #bfe1 #cjg-h72 though none of these 
excellent authorities seem either quite 
clear or quite satisfied with the       
notion2 and in the very passage referred
 to1 ,lyell may have possibly a much    
more philosophic notion in view1 where  
he says3 ,it is only necessary1 in order
 to explain the action of ,volcanoes1 to
 discover some cause which is capable of
 bringing about such a concentration of 
heat as may melt one after the other    
certain portions of the solid crust1 so 
as to form seas1 lakes or oceans of     
subterraneous lava4 7,vol4 ,,ii1 pp4    
#bbf1 #bbg74 ,if by this is meant1 that 
all that is needed to complete a true   
theory of volcanic action is to discover
 an adequate cosmical cause for the     

heat--that is to say1 a prime mover to  
which all its phenomena may be traced   
back1 which shall be at once            
reconcilable with the conditions of our 
planet as a cooling mass in space and   
with facts of ,vulcanology as they are  
now seen upon it--then ,i entirely agree
 with it4  ,it has been my own object to
 endeavour to discover and develope that
 adequate cause in a ,paper ,on         
,volcanic ,energy1 an ,attempt to       
develope its ,true ,nature and ,cosmical
 ,relations1 read 7in abstract7 before  
the ,royal ,society of ,london          
7,proceedings1 ,royal ,society1 ,vol4   
,,xx41 ,may1 #ahgb71 and now 7,october1 
#ahgb7 under consideration of ,council  
with a view to publication4  ,i propose 
concluding this review of the progress  
of ,vulcanology 7in which ,i have had to
 limit myself to reviewing merely the   
chief stages of advance towards         
knowledge of the nature and origin of   
volcanic heat itself1 and have had to   
pass without notice the vast and        

important mass of facts and reasonings  
collected by so many labourers as to its
 visible phenomena and products1 and the
 still greater mass of speculation1 good
 and bad1 on every branch of the        
subject71 by giving a necessarily very  
brief and imperfect sketch of my own    
views as in that ,paper in part         
developed4 ,it will first be necessary  
to retrace our steps a little1 in order 
to gain such a point as shall afford us 
a fuller view of the whole problem      
before us4  ,it is not necessary to     
dilate1 even did space allow1 upon the  
many points which bind together         
,earthquakes and ,volcanoes as belonging
 to the play of like forces4 ,these are 
generally admitted2 and in various ways1
 more or less obscure1 geologists       
generally have supposed some relations  
between these and the forces of         
elevation1 which have raised up mountain
 chains1 etc4  ,no one1 however1 that ,i
 am aware of1 prior to myself1 in the   
,paper just alluded to1 has attempted to

 show1 still less to prove upon an      
experimental basis1 that all the        
phenomena of elevation1 of volcanic     
action1 and of ,earthquakes1 are        
explicable as parts of one simple       
machinery--namely1 the play of forces   
resulting from the secular cooling of   
our globe4 ,we have seen that1 on the   
whole1 both ,earthquakes and ,volcanoes 
follow along the great lines of         
elevation of our surface4 ,any true     
solution of the play of forces which has
 produced any one of those three classes
 of phenomena must connect itself with  
them all1 and be adequate to account for
 all4 ,and this would have earlier been 
seen1 had geologists generally framed   
for themselves any correct notions of   
the mechanism of elevation itself1 and  
seen its real relation with the secular 
cooling of our planet4 ,but the play of 
forces resulting from this secular      
cooling has never1 until very recently1 
been adequately or truly stated4 ,the   
arbitrary assumption and neglect of     

several essential conditions by ,la     
,place1 in his celebrated ,paper ,on the
 ,cooling of the ,earth1 in the fifth   
volume of the ,mcanique ,cleste1 and the
 arbitrary and unsustainable hypothesis 
of ,poisson upon the same subject1 have 
tended to retard the progress of        
physical ,geology as to the nature of   
elevation3 the first1 by leaving the    
geologist in doubt as to whether our    
globe were cooling at all2 the second1  
by suggesting distorted notions as to   
the mode of its cooling and             
consolidation4 ,on the other hand1      
neither geologists nor mathematicians   
generally have framed for themselves any
 clear notions of the mechanism of      
elevation4 ,had a true conception been  
formed of the forces and interior       
movements brought necessarily into      
operation by the secular cooling of the 
globe1 geologists could scarcely have   
failed to see that their notion as to   
the way and direction in which the      
forces producing elevation have actually

 acted could not1 if arising from       
refrigeration1 be those which they have 
almost universally supposed1            
namely--some force acting vertically    
upwards1 i4e41 radially from the centre 
of the sphere4 ,had geologists only     
looked at ,nature with open eye1 they   
must have seen that mountain ranges1 and
 elevations generally 7exclusive of     
volcanic cones71 presented circumstances
 absolutely incompatible with their     
having been thrust up by any force      
primarily acting in the direction of a  
radius to the spheroid4  ,yet this is   
the erroneous notion of the mechanism of
 elevation which to the present hour    
prevails amongst geologists1 so far as  
they in general have framed to          
themselves any distinct idea of such    
mechanism at all4  ,thus1 only to cite  
two examples from recent authors of     
justly high reputation4 ,lyell says of  
the probable subterranean sources1      
whether of upward or downward movement1 
when permanently uplifting a country1   

and in reference to the crumpling of    
strata on mountain flanks by lateral    
pressure1 it would be rash to assume    
these able to resist a power of such    
stupendous energy1 if its direction1    
instead of being vertical1 happened to  
be oblique or horizontal4 ,this is      
somewhat vague--and ,i trust ,i do not  
mistake or misrepresent the illustrious 
author--yet it is the most explicit     
expression ,i can find in the           
,principles of ,geology as to his notion
 of the primary direction of elevatory  
force 7,edit4 #aj1 ,vol4 ,i41 p4 #acc74 
,that ,mr4 ,scrope's idea is that only  
of primary radial or vertical direction 
of such forces1 is apparent on          
inspecting his ,diagram ,no4 #fd        
7,volcanoes1 p4 #bhe71 and in the use of
 the words1 an axial wedge of granite1  
which1 on the next page1 we find is     
liquefied granite2 and if we read on to 
page #bid1 and refer also to pages #ej  
and #ea1 ,i believe there can be no     
doubt that vertical or direct up-thrust 

is the author's notion of the primary   
direction of all forces of elevation4   
,the true nature of these forces was1   
however1 clearly seen and most justly   
stated by ,constant ,prevost 7,compt4   
,rend41 ,tome ,,xxxi41 #ahej1 and       
,bulletin de la ,socit ,golog4 de       
,france1 ,tome ,,ii41 #ahdj7 as         
consisting1 not in forces of some       
unknown origin acting primarily in the  
vertical1 but in tangential pressures   
acting horizontally1 and resolved by    
mutual pressures at certain points into 
vertical resultants4 ,these ,prevost    
rightly attributed to the contraction of
 the earth's solid crust4 ,the same idea
 has been adopted by ,elie de ,beaumont 
as the true mechanism of the elevation  
of mountain ranges2 and although ,de    
,beaumont's views as to the thinness he 
assigns to the solid and contracting    
crust1 and his strange deduction as to  
the parallelism of contemporaneous      
mountain chains uplifted by its         
spasmodic action along certain lines1   

may be untenable1 his notion generally  
as to the play of forces producing      
mountain elevation is much more nearly  
correct4  ,mr4 ,hopkins's notion is     
simply that of the geologists4 ,anyone  
who reads his well-known papers on      
elevation and the formation of fissures1
 etc41 must see that he views all       
elevatory forces as of liquids or       
quasi-liquids forced up and acting      
primarily vertically upon the strata    
above them1 and that these strata are   
not under tangential compression1 but   
under tension4 ,hence the mathematical  
deductions contained in those papers as 
to the directions in which elevatory    
forces act1 and in which fissures are   
formed by them1 are not in any way a    
setting forth of such facts as occur in 
,nature1 and1 much attention as they    
have attracted1 can only now be viewed  
as exercises of mathematical skill      
misapplied1 because based upon data not 
to be found in ,nature4 ,in fact1 those 
papers do but misrepresent ,nature1 and1

 like many other mathematical           
investigations based on untrue or       
insufficient data1 have tended to retard
 knowledge4  ,the views which ,i have   
put forward in the ,paper ,i have       
referred to1 read to the ,royal         
,society1 recapitulated in skeleton1 so 
to say1 are as follows4 ,omitting those 
portions which treat of our globe from  
the period of the first liquefaction out
 of a nebulous condition1 and of the    
earliest stages of the cooling by       
radiation into space1 when the crust was
 extremely thin1 and of the deformation 
of the spheroid as one of the first     
effects of its contraction1 and through 
that the general shaping out of         
continents and ocean beds2 ,i have      
endeavoured to show that the rate of    
contraction of the crust1 while very    
thin1 exceeded that of the large fluid  
nucleus supporting it1 and so gave rise 
to tangential tensions in the crust1 and
 fracturing it into segments2 next1 that
 as the crust thickened1 these tensions 

were gradually converted into tangential
 pressures1 the contraction of the      
nucleus now beginning to exceed 7for    
equal losses of heat7 that of the crust 
through which it cooled4 ,at this stage 
these tangential pressures gave rise to 
the chief elevations of mountain        
chains--not by liquid matter by any     
process being injected from beneath     
vertically1 but by such pressures1      
mutually reacting along certain lines1  
being resolved into the vertical1 and   
forcing upwards more or less of the     
crust itself4 ,the great outlines of the
 mountain ranges and the greater        
elevation of the land were designated   
and formed during the long periods that 
elapsed in which the continually        
increasing thickness of crust remained  
such that it was still1 as a whole1     
flexible enough1 or opposed sufficiently
 little resistance to crushing1 to admit
 of this uprise of mountain chains by   
resolved tangential pressures4 ,i have  
shown that the simple mechanism of such 

tangential pressures is competent to    
account for all the complex phenomena   
both of the elevations and of the       
depressions that we now see on the      
earth's surface 7other than continents  
and ocean beds71 including the          
production of gaping fissures 7in       
directions generally orthogonal to those
 of tangential pressure74 ,and as our   
earth is still a cooling body1 and the  
crust1 however now thicker and more     
rigid1 is still incapable of sustaining 
the tangential pressures to which it is 
now exposed1 so ,i by no means infer    
that slow and small 7relatively7        
movements of elevation and depression   
may not be still and now going on upon  
the earth's surface2 in fact all the    
phenomena of elevation and depression1  
rending1 etc41 which at a much remoter  
epoch acted upon a much grander and more
 effective scale4 ,so that1 for aught my
 views say to the contrary1 all the     
mountain chains in the world may be     
possibly increasing in stature year by  

year1 or at times2 but in any case at a 
rate almost infinitesimally small in its
 totality over the whole earth to that  
with which their ridges were originally 
upreared4  ,but the thickness of the    
earth's crust--thus constantly added to1
 by accretion of solidifying matter from
 the still liquid or pasty nucleus1 as  
the whole mass has cooled--has now      
assumed such a thickness as to be able  
to offer a too considerable resistance  
to the tangential pressures1 to admit of
 its giving way to any large extent by  
resolution upwards2 yet the cooling of  
the whole mass is going on1 and         
contraction1 though unequal1 both of    
thick crust and of hotter nucleus       
beneath also1 whether the latter be now 
liquid or not4 ,were the contraction1   
lineal or cubical1 for equal decrements 
or losses of heat1 or in equal          
times--equal both in the material of the
 solidified crust and in that of the    
hotter nucleus--there could be no such  
tangential pressures as are here        

referred to1 at any epoch of the earth's
 cooling4 ,but in accordance with the   
facts of experimental physics1 we know  
that the co-efficient of contraction for
 all bodies is greater as their actual  
temperature is higher1 and this both in 
their solid and liquid states4  ,hence  
for equal decrements of heat1 or by the 
cooling in equal times1 the hotter      
nucleus contracts more than does its    
envelope of solid matter4  ,the result  
is now1 as at all periods since the     
signs changed of the tangential forces  
thus brought into play--i4e41 since they
 became tangential pressures--that the  
nucleus tends to shrink away as it were 
from beneath the crust1 and to leave the
 latter1 unsupported or but partially   
supported1 as a spheroidal dome above   
it4  ,now what happens8 ,if the hollow  
spheroidal shell were strong enough to  
sustain1 as a spheric dome1 the         
tangential thrust of its own weight and 
the attraction of the nucleus1 the shell
 would be left behind altogether by the 

nucleus1 and the latter might be        
conceived as an independent globe       
revolving1 centrally or excentrically1  
within a shell outside of it4 ,this1    
however1 is not what happens4  ,the     
question then arises1 ,can the solid    
shell support the tangential thrust to  
which it would be thus exposed8 ,by the 
application to this problem of an       
elegant theorem of ,lagrange1 ,i have   
proved that it cannot possibly do so1 no
 matter what may be its thickness nor   
what its material1 even were we to      
assume the latter not merely of the     
hardest and most resistant rocks we know
 anything of1 but even were it of       
tempered cast-steel1 the most resistant 
substance 7unless possibly iridio-osmium
 exceed it7 that we know anything about4
 ,lagrange has shown that if ,p be the  
normal pressure upon any flexible plate 
curved in both directions1 the radii of 
these principal curvatures being r' and 
r''1 and ,t the tangential thrust at the
 point of application and due to the    

force ,p1 then3       ,p  ,t 7#a_/r'    
#a_/r''7  ,when the surface is          
spherical1 or may be viewed as such1 r' 
r'' and       ,p  #b,t_/r or1 ,t  ,p    
r_/#b  ,in the present case ,p is for a 
unit square 7taken relatively small and 
so assumed as plane7 of the shell1      
suppose a square mile1 equal to the     
effect of gravity upon that unit1 r     
being the earth's radius1 and if we     
assume the unit square be also a unit in
 thickness1 ,p is then the weight of a  
cubic mile of its material2 and if we   
take 7roughly7 the earth's radius as    
#d1jjj miles1 the tangential pressure1  
,t1 is1 on each face of the cubic mile1 
equal to       7#djjj_/b7 ,p1  or equal 
to the pressure of a column of the same 
material of #b1jjj times its weight4    
,if the cubic mile that we have thus    
supposed cut out of the earth's crust at
 the surface were of the hardest known  
granite or porphyry1 it would be exposed
 to a crushing tangential pressure equal
 to between #djj and #ejj times what it 

could withstand1 and so must crush1 even
 though only left unsupported by the    
nucleus beneath1 to the extent of       
#a_/djj or #a_/ejj of its entire weight4
 ,and what is true here of a mile taken 
at the surface1 is true 7neglecting some
 minute corrections for difference in   
the co-efficient of gravity1 etc47 if   
taken at any other depth within the     
thick crust4,f  ,the crust of our earth1
 then1 as it now is1 must crush1 to     
follow down after the shrinking         
nucleus--if so be that the globe be     
still cooling1 and constituted as it is2
 even to the limited extent to which we 
know anything of its nature--it must    
crush unequally1 both regarded          
superficially and as to depth2 generally
 the crushing lines being confined to   
the planes or places of greatest        
weakness2 and the crushing will not be  
absolutely constant and uniform         
anywhere1 or at any time1 or at any of  
those places of weakness to which it    
will be principally confined1 but will  

be more or less irregular1              
quasi-periodic1 or paroxysmal3 as is1   
indeed1 the way in which all known      
material substances 7more or less rigid7
 give way to a slow and constantly      
increasing1 steady pressure4  ,we have  
now to ask1 ,how much of this crushing  
is going on at present year by year8    
,and the answer to this depends upon    
what amount of heat our world is losing 
into space year by year4  ,geologists   
who have taken on trust the statement1  
that ,la ,place has proved that the     
world has lost no sensible amount of    
heat for the last #aj1jjj years seem    
generally to suppose that to be a fact2 
but in reality ,la ,place has proved    
nothing of the sort1 as those geological
 teachers who have echoed the conclusion
 should have known1 had they deciphered 
the mathematical argument upon which it 
has been supposed to rest4  ,by         
application of ,fourier's theorem 7or   
definition7 to the observed rate of     
increment of heat in descending from the

 geothermal couche of invariable        
temperature1 and the co-efficients of   
conductivity of the rocks of our earth's
 crust1 as given by the long-continued  
observations made beneath the           
,observatories of ,paris and of         
,edinburgh1 it results that the annual  
loss of heat into space of our globe at 
present is equal to that which would    
liquefy into water1 at #cb ,fahr41 about
 #ggg cubic miles of ice2 and this is   
the measuring unit for the amount of    
contraction of our globe now going on4  
,the figures are not probably exact1 for
 the data are not on a basis            
sufficiently full or exactly established
 as yet2 but they are not very widely   
wrong1 and their precise exactness is   
not material here4 ,now1 how is this    
annual loss of heat 7great or small1 as 
we may please to view it7 from the      
interior of our globe disposed of8      
,what does it do in the interior8 ,we   
have already seen that it is primarily  
disposed of by conversion into work2    

into the work of diminishing the earth's
 volume as a whole1 and in so doing     
crushing portions of the solid          
surrounding shell4  ,but does the       
transformation of lost heat into the    
work of vertical descent1 and of the    
crush as it follows down after the      
shrinking nucleus1 end the cycle8 ,no4  
,a very large portion of the mechanical 
work thus produced1 and resolved1 as we 
have seen1 into tangential crushing     
pressure1 is retransformed into heat    
again in the very act of crushing the   
solid material of the shell4 ,if we see 
a cartload of granite paving-stones shot
 out in the dark1 we see fire and light 
produced by their collision2 if we rub  
two pieces of quartz together1 and crush
 thus their surfaces against each other1
 we find we heat the pieces and evolve  
light4  ,the machinery used for crushing
 by steam-power1 hard rocks into road   
metal1 gets so hot that the surfaces    
cannot be touched4  ,these are familiar 
instances of one result of what is now  

taking place by the crushing of the     
rocky masses of our cooling and         
descending earth's crust1 every hour    
beneath our feet1 only upon a vastly    
greater scale4 ,it is in this local     
transformation of work into heat that ,i
 find the true origin of volcanic heat  
within our globe4 ,but if we are to test
 this1 so as in the only way possible to
 decide is it a true solution of this   
great problem1 we must again ask the    
question1 ,how much8 and to answer this1
 we must determine experimentally how   
much heat can be developed by the       
crushing of a given volume1 say a cubic 
mile1 of such rocky materials as we know
 must constitute the crust of our globe 
down to the bottom of the known         
sedimentary strata1 and extending to    
such crystalloid rocks as we may presume
 underlie these4 ,we must also obtain at
 least approximately what are the       
co-efficients of total contraction      
between fusion and atmospheric          
temperature of such melted rocks1 basic 

and acid silicates1 as may be deemed    
representative of that co-efficient for 
the range of volcanic fused products1   
basalts1 trachytes1 etc41 which probably
 sufficiently nearly coincide with that 
of the whole non-metallic mass of our   
globe4  ,the first ,i have determined   
experimentally by two different methods1
 but principally by the direct one of   
the work expended in crushing prisms of 
sixteen representative classes of rock2 
the specific gravities and specific     
heats of which ,i have also determined4 
,if ,h be the height of a prism of rock 
crushed to powder by a pressure1 ,p1    
applied to two opposite faces1 which1   
when the prism has been reduced to its  
volume in powder1 has acted through a   
range of ,h - t1 then       ,p  7,h - t7
 _/ #ggb  is the heat corresponding to  
the work expended in the crushing1      
expressed in ,british units of heat4    
,the following were the rocks           
experimented upon3 ,caen stone1         
,portland 7both oolites71 magnesian     

limestone1 sandstones of various sorts1 
carboniferous limestones 7marbles71 the 
older slates 7,cambrian and ,silurian71 
basalts1 various granites and           
porphyries1 thus ranging from the newest
 and least resistant to the oldest and  
most resistant rocks4 ,the results have 
been tabulated1 and are given in detail 
in my ,paper1 now in possession of the  
,royal ,society4 ,the minimum obtained  
is #cca and the maximum #g1hfg ,british 
units of heat developed1 by             
transformation of the work of crushing  
one cubic foot of rock4 ,if we apply the
 results to a thickness of solid crust  
of #ajj miles 7,british71 of which the  
upper twenty-one miles consist of       
neozoic1 newer palozoic1 older palozoic 
and azoic rocks in nearly equal         
proportion as to thickness1 and the     
remaining eighty miles of crystalloid   
rocks 7acid and basic magmas of         
,durocher7 of physical properties which 
we may assume not very different from   
those of our known granites and         

porphyries--and which1 in so far as they
 may differ1 would give a still higher  
co-efficient of work transformed into   
heat than ,i have attributed to them by 
ranging them as only equal to the       
granites1 etc4--then we obtain a mean   
co-efficient for the entire thickness of
 crust of #ajj miles of #f1dgb ,british 
units of heat1 developable from each    
cubic foot of its material1 if crushed  
to powder4 ,it results from this that   
each cubic mile of the mean material of 
such a crust1 when crushed to powder1   
developes sufficient heat to melt #jhgf 
cubic miles of ice into water at #cb1 or
 to raise #gfjj cubic miles of water    
from #cb to #bab ,fahr41 or to boil off 
#aabd cubic miles of water at #cb into  
steam of one atmosphere1 or1 taking the 
average melting point of rocky mixtures 
at #b1jjj ,fahr41 to melt nearly three  
and a-half cubic miles of such rock1 if 
of the same specific heat4  ,of the heat
 annually lost by our globe and         
dissipated into space1 represented by   

#ggg cubic miles of ice melted1 as      
before stated1 the chief part is derived
 from the actual hypogeal source of a   
hotter though not necessarily fused     
nucleus1 and nearly1 if not wholly1 is  
quite independent of the heat of        
,vulcanicity1 which is developed as a   
consequence of its loss or dissipation4 
,but were we to take the extreme case1  
and suppose it possible that all the    
heat the globe loses annually resulted  
from the transformation of the work of  
internal crushing of its shell1 we shall
 find that the total volume of rock     
needed to be crushed in order to produce
 the required amount of lost heat is    
perfectly insignificant as compared with
 the volume of the globe itself1 or that
 of its shell4 ,for1 as #abgj cubic     
miles of crushed rock developes heat    
equivalent to that required to melt one 
cubic mile of ice to water at #cb1 and  
if we assume the volume of our globe's  
solid crust to equal one-fourth of the  
total volume of the entire globe1 #ihg  

cubic miles of rock crushed annually    
would supply the whole of the heat      
dissipated in that time4 ,but that is   
less than the one sixty-five millionth  
of the volume of the crust only4  ,but a
 very small portion of the total heat   
annually lost by our globe is sufficient
 to account for the whole of the        
volcanic energy of every sort1 including
 thermal waters1 manifested annually    
upon our earth4 ,in the absence of      
complete data1 we can only approximately
 calculate what is the annual amount of 
present volcanic energy of our planet4  
,this energy shows itself to us in three
 ways3 #a4 ,the heating or fusing of the
 ejected solid matters at volcanic      
vents4 #b4 ,the evolution of steam and  
other heated elastic fluids by which    
these are carried4 #c4 ,the work of     
raising through a certain height all the
 materials ejected4 ,to which we must   
add a large allowance for waste1 or     
thermal mechanical and chemical energy  
ineffectually dissipated in and above   

the vents4 ,all these are measurable    
into units of heat4  ,i have applied    
this method of calculation to test the  
adequacy of the source ,i have assigned 
for volcanic heat1 in two ways1 viz43   
#a4 ,to the phenomena presented during  
the last two thousand years by          
,vesuvius1 the best known ,volcano in   
the world2 and #b4 ,to the whole of the 
four hundred and odd volcanic cones     
observed so far upon our globe1 of which
 not more than one-half have ever been  
known in activity4  ,it is impossible   
here to refer to the details of the     
method or steps of these calculations4  
,the result however is1 that making     
large allowances for presumably         
defective data1 less than one-fourth of 
the total telluric heat annually        
dissipated 7as already stated in amount7
 is sufficient to account for the annual
 volcanic energy at present expended by 
our globe4  ,it is thus represented by  
the transformation into heat of the work
 of crushing about #bdg cubic miles of  

7mean7 rock1 a quantity so perfectly    
insignificant1 as compared with the     
volume of the globe itself1 as to be    
absolutely inappreciable in any way but 
by calculation2 and as its mechanical   
result is only the vertical             
transposition transitorily of material  
within or upon our globe1 the proportion
 of the mass of which to the whole is   
equally insignificant1 so not likely in 
any way to produce changes recognisable 
by the astronomer4  ,space here forbids 
my entering at all upon that branch of  
my investigation which is based upon the
 experimental results1 above mentioned1 
of the total contraction of fused rocks3
 for these1 the original ,paper can1 ,i 
hope1 be hereafter referred to4 ,i am   
enabled1 however1 to prove thus how     
enormously more than needful has been   
the store of energy dissipated since our
 globe was wholly a melted mass1 for the
 production1 through the contraction of 
its volume1 of all the phenomena of     
elevation and of ,vulcanicity which its 

surface presents4 ,and how very small is
 the amount of that energy in a unit of 
time as now operative1 when compared    
with the same at very remote epochs in  
our planet's history4  ,i have said that
 if we can find a true cause in ,nature 
for the origination of volcanic heat1   
all the other known phenomena1 at and   
about volcanic vents1 become simple4    
,lavas and all other solid ejecta of    
,volcanoes1 from all parts of the       
earth's surface1 as well as basalts1    
present in chemical and physical        
constitution close resemblance1 and may 
be all referred to the melting of more  
or less fusible mixtures of siliceous   
crystalloid rocks with aluminous        
7slates1 etc47 and calcareous rocks4    
,their general chemical composition1 and
 the higher or lower temperatures of    
fusion resulting therefrom1 together    
with the higher or lower temperatures to
 which they have been submitted at the  
different volcanic foci1 determine their
 difference of flow 7under like surface 

conditions7 and of mineral character    
after ejection and cooling4  ,st4 ,clair
 de ,ville and ,fouqu have shown that   
the gaseous ejections1 of which steam   
forms probably #ii per cent41 are such  
as arise from water admitted to a       
pre-existent focus of high temperature4 
,whether sea or fresh water is not      
material1 when we bear in mind that the 
chemical constituents found in sea water
 and in natural fresh waters that have  
penetrated the soil are1 on the whole1  
alike in kind and only differ in        
proportions4 ,but ,i must pass almost   
without notice all the varied and       
instructive phenomena which are         
presented by volcanic vents1 for to     
treat of these at all would be to more  
than double the size of this sketch4    
,in the source that has been pointed out
 as that from which volcanic heat itself
 is derived1 viz41 the secular cooling  
of our globe1 and the effects of that   
upon its solid shell1 we are enabled to 
point to that which is the surest test  

of the truth of any theory--that it not 
only enables us to account for all the  
phenomena1 near or remote1 but to       
predict them4 ,we see here linked       
together as parts of one grand play of  
forces1 those of contraction by cooling1
 producing by direct mechanical action  
the elevation of mountain chains1 and by
 their indirect action1 by              
transformation of mechanical work into  
heat1 the production of ,volcanoes2 and 
both by direct and by indirect action1  
of ,earthquakes1 never previously shown 
to have thus the physical connection of 
one common cause1 but merely supposed1  
more or less1 to be connected by their  
distribution upon our earth's surface4  
,we now discern thus the physical cause 
why ,volcanoes are distributed1 viewed  
largely1 linearly1 and follow the lines 
of elevation2 we see equally why their  
action is uncertain1 non-periodic1      
fluctuating in intensity1 with longer or
 shorter periods of repose1 shifting in 
position1 becoming extinct here1        

appearing in new activity or for the    
first time there4 ,we have an adequate  
solution of the before inexplicable fact
 of their propinquity1 and yet want of  
connection4 ,we have an adequate cause  
for the fusion of rock at local points  
without resorting to the baseless       
hypothesis of perennial lakes of lava1  
etc4  ,for the first time1 too1 we      
discern a true physical cause for       
earthquake movement1 where volcanic     
energy does not show itself4 ,the       
crushing of the world's solid shell1    
whether thick or thin1 goes on per      
saltum and at ever-shifting places1     
however steadily the tangential         
pressures producing it may act4 ,hence  
crushing alone may be shown to develope 
amply sufficient impulse to produce the 
most violent ,earthquakes1 whether they 
be or be not at a given place or time   
connected with volcanic outburst or     
possible injection1 or with tangential  
pressures1 enough still1 in some cases1 
to produce partial permanent elevation4 

,when subterraneous crushing takes      
place1 and the circumstances of the site
 do not permit the access of water1     
there may be ,earthquake1 but can be no 
,volcano2 where water is admitted1 there
 may be both4  ,and thus we discern why 
there are comparatively few submarine   
,volcanoes1 the floor of the ocean      
being1 on the whole1                    
water-tight--puddled1 as an engineer    
would say1 by the huge deposit of       
incoherent mud1 etc41 that covers most  
of it1 and probably having a thicker    
crust beneath it than beneath the land4 
,we see1 moreover1 that the geological  
doctrine of absolute uniformity cannot  
be true as to ,vulcanicity1 any more    
than it can for any other energy in play
 in our world4 ,its development was     
greatest at its earliest stages1 when   
the great masses of the mountain chains 
were elevated4 ,it is even now--though  
as compared to men's experience1 and    
even to all historic time1 apparently   
uniform and always the same--a decaying 

energy4  ,the regimen of our planet as  
part of the ,cosmos1 which seems to some
 absolute 7and presented to ,playfair no
 trace of a beginning nor indication of 
an end71 is not absolute1 and only seems
 to us to be so because we see so little
 of it1 and of its long perspective in  
time4 ,this the now established doctrine
 of the conservation of energy renders  
certain4  ,with this source for volcanic
 heat1 too1 in our possession1 we can   
look from our own world to others1 and  
predict within certain limits1 which    
must widen as our knowledge of the facts
 of their substance and surface becomes 
greater1 what have been and what are the
 developments of ,vulcanicity which have
 taken place or are occurring in or upon
 them4 ,looking to our own satellite1 we
 see for the first time a sufficient    
physical cause for the enormous display 
of volcanic energy there which the      
telescope divulges to us2 one which is  
not to be explained alone by the        
commonly made statement of the small    

density of the moon1 but by the fact    
that as the rate of her cooling from a  
given temperature1 as compared with that
 of our earth 7apart from questions of  
the chemical nature of the two bodies1  
or of their specific heats1 etc471 has  
been inversely as their respective      
masses1 and directly as their surfaces1 
so has the rate of cooling of the moon  
been vastly greater than that of the    
earth1 and the energy due to contraction
 by cooling more intense and rapidly    
developed in our satellite than upon our
 globe4  ,we have thus traced1 in meagre
 and broken outline only--because space 
admitted no more--the progress of       
,science to its existing state as       
respects ,vulcanicity1 in its two       
branches of ,vulcanology and of         
,seismology1 and pointed out their more 
intimate relations and points of        
connection1 and been at length able to  
refer them1 on the sure basis of        
physical laws1 to one common cause1 and 
that one derived from no hypothesis1 but

 simply from the postulate of our world 
as a terr-aqueous globe cooling in      
space4  ,what ,i have here advanced with
 reference to volcanic energy1 which    
appertains to my own researches1 ,i do  
not conceal from myself1 nor from the   
reader1 has yet to await the reception  
generally and the award of the true men 
of science of the world4  ,that1 like   
every new line of thought which has     
attempted or succeeded in supplanting   
the old1 it will meet with opposition1  
,i make no doubt4  ,my belief1 however1 
is that in the end it will be found to  
have added a fragment to the edifice of 
true knowledge4  ,the interpretation    
which ,i have given of the nature and   
origin of volcanic activity points at   
once to the function in the ,cosmos     
which it is its destiny to fulfil4 ,it  
is the instrument provided for the      
purpose of continually preserving the   
earth's solid shell in a state to follow
 down after the descending nucleus4 ,it 
does this by an apparatus or play of    

mechanism whereby the material of the   
solid shell1 locally or along certain   
lines1 is not only crushed1 but the     
crushed material is blown out as dust1  
or expelled as liquid rock from between 
the walls of the shell1 which are thus  
enabled to approach each other2 and     
thus1 by relief of the tangential       
thrusts1 to permit the shell to descend1
 which it is obvious that crushing      
alone1 unless it extended to the whole  
mass of the shell1 could not accomplish4
  ,it is a wonderful example of         
,nature's mechanism thus to see how     
simple are the means by which this end  
is accomplished4 ,the same inevitable   
crush that dislocates the solid shell   
along certain lines1 produces the heat  
necessary to expel to the surface the   
material crushed4  ,when attempted to be
 made the basis for philosophic         
discovery1 final causes are no doubt    
barren1 as ,bacon has said2 but when we 
have independently and by strict methods
 arrived at a result1 we may justly     

appeal1 as a test of its truth1 to its  
showing itself as plainly fulfilling a  
needful end1 and1 by a distinctly       
discernible mechanism1 preserving that  
harmony and conservation which are the  
obvious law of the universe4  ,as has   
been said1 if ,i mistake not by         
,daubeny1 ,john ,phillips1 by           
,herschell1 and by myself1 the function 
of the ,earthquake and the ,volcano is  
not destructive but1 preservative4 ,but 
we now see that3 that the preservative  
scope of this function1 as respects our 
earth1 is far wider than what has been  
previously attributed to it4 ,the       
,volcano does not merely throw up new   
fertile soil1 and tend1 in some small   
degree1 to restore to the dry land the  
waste for ever going on by rain and sea2
 it fulfils a far weightier and more    
imperative task2 it--by a mechanism the 
power of which is exactly balanced to   
the variable calls demanded of it1 and  
which working almost imperceptibly1     
although in a manner however terrible   

its surface-action may at times appear  
to us little men,g--prevents at longer  
intervals such sudden and unlooked-for  
paroxysms in the mass of our subsiding  
earth's shell as would be attended with 
wide-spread destruction to all that it  
inhabit4  ,to the popular mind1         
,volcanoes and ,earthquakes are only    
isolated items of curiosity amongst the 
wonders of the world3 few geologists    
even appear to realise how great and    
important are the relations of          
,vulcanicity to their science1 viewed as
 a whole4 ,yet of ,vulcanicity it is not
 too much to say1 that in proportion as 
its nature and doctrines come to be     
known and understood as parts of the    
,cosmos1 the nearer will it be seen to  
lie at the basis of all ,physical       
,geology4   ,a ,for a fuller account of 
the literature and history of           
advancement of human knowledge as to    
,earthquakes1 here merely glanced at1 ,i
 must refer to my ,first ,report on the 
,facts of ,earthquakes1 ,reports1       

,british ,association1 #ahej1 and to the
 works of ,daubeny1 ,lyell1 ,phillips   
and others1 its complete history        
remaining yet to be written4  ,b ,yet   
how indistinctly formed were ,young's   
ideas1 and indistinct in the same       
direction as those of ,humboldt1 becomes
 evident by a single sentence3 ,when the
 agitation produced by an ,earthquake   
extends further than there is any reason
 to suspect a subterraneous             
communication1 it is probably propagated
 through the earth nearly in the same   
manner as a noise is conveyed through   
the air4--,lectures1 ,nat4 ,phil41 ,vol4
 ,i4  ,c ,the ,right ,rev4 ,charles     
,graves1 ,f4,r4,s41 etc41 then ,fellow  
of ,trinity ,college1 ,pres4 ,r4 ,i4    
,acad41 and now ,bishop of ,limerick1 on
 presentation of the ,academy's         
,cunningham ,medal4  ,d ,in this        
,report1 though ,i have never before    
referred to it1 and do so now with      
reluctance1 ,i have always felt that the
 ,author did me some injustice4 ,the    

only reference made to my labours1      
published the preceding year only1 is in
 the following words3 ,many persons have
 regarded these phenomena 7viz41        
,earthquakes7 as due in a great measure 
to vibrations 444 and the subject has   
lately been brought under our notice1 in
 a ,memoir by ,mr4 ,mallet1 ',on the    
,dynamics of ,earthquakes1' in which he 
has treated it in a more determinate    
manner1 and in more detail1 than any    
preceding writer 7p4 #gd74 ,if that     
,paper of mine be collated with this    
,report1 it will be1 ,i believe1 found  
that1 as respects the earthquake part1  
the latter tint parades1 in a           
mathematical dress1 some portions of the
 general theory of earthquake movements1
 previously published by me as above    
stated4 ,so1 also1 in the chapter 7p4   
#ij7 referring to ,seismometry1 and the 
important uses to ,geology that might be
 7and since have been1 to some extent7  
made of it1 no mention is made of those 
instruments previously proposed by me1  

nor of my anticipation of their         
important uses4 ,this is but too        
mortifyingly suggestive of the--        
,pereant qui mea ante mihi dixerunt4    
,having left this unnoticed for so many 
years1 and during which the ,author has 
preceded me to that bourne where our    
errors to each other must be forgotten1 
,i should certainly not have now        
trespassed on the good rule1 ,de mortuis
 nil nisi bonum1 had ,i not observed    
very recently one amongst other results 
probably attributable to it4 ,in        
,professor ,phillips's ,vesuvius1 if any
 one will refer to the passage beginning
 ,the mechanism of earthquake movement  
has been investigated by competent      
hands4 ,the late eminent mathematician1 
,mr4 ,hopkins1 explained these tremors  
in the solid earth by the general theory
 of vibratory motion1 etc4 7pages       
#beg-bei7--;,i think he must1 in the    
absence of collateral information1      
conclude that1 not ,i1 but ,mr4         
,hopkins1 was the discoverer of the     

,theory of ,earthquakes as explained by 
the general theory of vibratory motion4 
,probably my friend1 ,professor         
,phillips1 had not recently referred to 
those ,memoirs and ,reports of          
twenty-four years back1 and ,i am       
thoroughly convinced that1 if he has    
here perpetuated an injustice1 he has   
done so unintentionally and unwittingly4
  ,still1 the facts show how true it is 
that       ,the ill men do lives after  
them1      ,the good they do is oft     
interred with their bones4  ,and ,i may 
venture to ask my friend1 should his    
admirable book reach1 as ,i doubt not it
 will1 another edition1 to modify the   
passage4  ,e ,assuming the point of     
ejection of this block 7the crater7 to  
be #h1jjj feet above where it landed1   
and allowing it as high a density as    
admissible1 and the angle of projection 
the best for large horizontal range1 it 
may be proved that this mass1 to reach  
nine miles horizontally1 would require  
an initial velocity of projection of    

from #a1ejj to #a1fjj feet per second1  
one as great as that of a smooth-bore   
cannon-shot at the muzzle1 and perfectly
 inconceivable to be produced by a      
volcano4  ,f ,the ,rev4 ,o4 ,fisher1    
,m4,a41 ,f4,g4,s41 in a most interesting
 and valuable ,paper1 ,on the ,elevation
 of ,mountain ,chains by ,lateral       
,pressure1 its ,cause1 and the ,amount  
of it1 with a ,speculation on the       
,origin of ,volcanic ,action1 read1     
,april1 #ahfh1 and published in the     
,transactions of the ,cambridge         
,philosophical ,society1 ,vol4 ,,xi41   
,part ,,iii41 in #ahfi1 has deduced the 
necessary crushing of the earth's crust 
by a different but closely analogous    
method4 ,i had not seen this ,paper     
until after my own was in the hands of  
the ,royal ,society4 ,the author's      
volcanic views are wholly different from
 my own1 and do not appear to me equally
 valid with his notions as to           
elevation4--,r4 ,m4  ,g ,magna ista quia
 parvi sumus--,,seneca1 ,qus4 ,nat4     

,,end4     ,,translation ,,of           
,,professor ,,palmieri',s  ,,account    
,,of ,,the ,,eruption ,,of ,,vesuvius   
,,of #ahga-ahgb     ,i4  ,,account ,,of 
,,the ,,eruption4   ,the great and      
disastrous conflagration of ,vesuvius1  
which took place on the #bfth of ,april1
 #ahgb1 was1 in my opinion1 the last    
phase of an eruption which commenced at 
the end of ,january1 #ahga1 an account  
of which ,i was unwilling to write1     
because ,i was convinced that it would  
not really terminate without a more or  
less violent explosion1 such as ,i had  
often predicted4 ,i shall now state the 
reasons upon which my prediction was    
founded4  ,when the central crater      
begins to heave1 with slight eruptions1 
one may always predict a series of      
slight convulsions of greater or less   
duration1 which are preparatory to the  
grand explosion1 after which the        
,volcano remains for the most part in   
repose4 ,thus1 when ,i observed the cone
 fissuring in ,november1 #ahfh1 and     

copious lava streams issuing from it1   
and flowing over the beautiful and      
fertile plains of the ,novelle1 through 
the ,fossa della ,vetrana1 instead of   
announcing the beginning of an eruption1
 ,i announced the termination of one    
which had been manifest for upwards of a
 year by the constant flow of lava from 
the summit of the cone4  ,from the month
 of ,november1 #ahfh1 until the end of  
,december1 #ahgj1 the mountain remained 
quiet1 except that the fumaroles at the 
head of the fissure showed a degree of  
activity by which chlorides and         
sulphides of copper1 sulphide of potash 
and other products1 were engendered4    
,but in the beginning of #ahga the      
seismograph was disturbed1#a and the    
crater discharged1 with a slight        
detonation1 a few incandescent          
projectiles4 ,then ,i announced that a  
new eruption had commenced1 which might 
be of long duration1 but with phases    
that could not possibly be foreseen2 and
 on the #acth ,january1 on the northern 

edge of the upper plain of the ,vesuvian
 cone1 an aperture appeared1 from which 
at first a little lava issued1 and then 
a small cone arose and threw out        
incandescent projectiles1 with much     
smoke of a reddish colour1 whilst the   
central crater continued to detonate    
more loudly and frequently4 ,the        
lava-flow continued to increase until   
the beginning of ,march1 without        
extending much beyond the base of the   
cone1 although it had great mobility4   
,in ,march1 this little cone appeared   
not only to subside1 but even partly to 
give way1 as almost happens with        
eccentric cones when their activity is  
at an end4 ,upon visiting it1 ,i        
observed that four prismatic or         
pillar-like masses remained standing1   
three of which were formed of scori     
which had fallen back again in a pasty  
condition1 and had become soldered      
together1 the fourth consisting of a    
pyramidal block of compact and lithoidal
 lava1 which appeared to have been      

forced up by impetus from the ground    
beneath4 ,a little smoke issued from the
 small crater1 and a loud hissing from  
the interior was audible4 ,by lying     
along the edge1 ,i could see a cavity of
 cylindrical form about ten metres in   
depth1 tapestried with stalactitic scori
 covered with sublimations of various   
colours4 ,the bottom of this crater was 
level1 but in the centre a small cone of
 about two metres had formed1 pointed in
 such a manner that it possessed but a  
very narrow opening at the apex1 from   
which smoke issued with a hissing sound1
 and from which were spurted a few very 
small incandescent scori4 ,this little  
cone increased in size as well as       
activity until it filled the crater1 and
 rose four or five metres above the     
brim4,a ,new and more abundant lavas    
appeared near the base of this cone1    
and1 pouring continually into the ,atria
 del ,cavallo1 rushed into the ,fossa   
della ,vetrana in the direction of the  
,observatory and towards the ,crocella1 

where they accumulated to such an extent
 as to cover the hill-side for a        
distance of about #cjj metres2 then     
turning below the ,canteroni1 they      
formed a hillock there without spreading
 much farther4 ,these very leucitic     
lavas are capable of great extension1   
the pieces which are ejected forming for
 the most part very fine filiform       
masses1 which may be collected on the   
mountain in great quantities1 and       
specimens of which ,i presented to the  
,academy under the name of filiform     
lapilli4 ,these threads were often of a 
clear yellowish colour1 and1 when       
observed under the microscope1 were     
found to consist of very minute crystals
 of leucite embedded in a homogeneous   
paste4 ,the crystals were still smaller 
as the diameter of the threads was less1
 and never formed knots or swellings    
even in the most hair-like threads4     
,these observations led me to reject the
 opinion of those who hold that crystals
 of leucite are pre-existent in the     

lava4 ,the viscous nature of these lavas
 prevented their being covered with     
fragmentary scori1 but caused the       
formation at first of a skin1 which1    
thickening1 became at last a more or    
less pliable shell1 that1 when more     
solidified1 allowed the still fluid part
 to run as in a tube formed of this     
solid shell4 ,for many months the lava  
descended thus from the cone and        
traversed the ,atria del ,cavallo1      
always covered1 appearing below the     
,canteroni of a lively fluidity1 until  
it could no longer be enveloped in its  
skin1 which was stretched by the        
addition of new lava1 and finally rent  
asunder to give room to the current     
until1 owing to diminished liquidity1 it
 was constrained to stop4 ,when the     
lava1 having traversed the covered      
channel it had made for itself from the 
top of the mountain to below the        
,canteroni1 made its appearance still   
running1 it frequently formed large     
bubbles on the surface1 which mostly    

burst to give vent to smoke1 and then   
disappeared4  ,in ,october1 #ahga1 near 
the edge of the central crater1 another 
small crater was formed by falling in1  
which1 after a few days1 gave vent to   
smoke and several jets of lava4 ,the    
principal cone frequently opened in some
 point of the slope to give egress to   
small currents of lava1 which quickly   
ceased4 ,but towards the end of ,october
 the detonations increased1 the smoke   
from the central crater issued more     
densely and mixed with ashes1 and the   
seismograph and accompanying apparatus  
were disturbed3 for all these reasons1  
,i said in one of my bulletins1 we have 
either reached a new phase or the end of
 the eruption1 not knowing whether the  
new phase would be the last4 ,on the    
#crd and #dth ,november copious and     
splendid lava streams coursed down the  
principal cone on its western side1 but 
were soon exhausted4 ,the cone of #ahga 
appeared again at rest1 and partly even 
fell in1 but did not cease to emit smoke

 and to show fire in the interior4  ,in 
the beginning of ,january1 #ahgb1 the   
little cone again became active1 the    
crater of the preceding ,october resumed
 strength1 with frequent bellowings and 
projectiles1 and soon after lavas of the
 same kind as before reappeared4 ,the   
cone of #ahga1 formed again by the lava 
ejected1 became so full that the lava   
poured from its summit in the most      
singular and enchanting manner4 ,so far 
only an eccentric or ephemeral cone had 
risen close to the central crater1      
which1 after exhaustion1 regained vigour
 and discharged lava from the apex      
instead of the base1 as usually happens4
  ,in the month of ,february matters    
were somewhat moderated2 but in ,march1 
with the full moon1 the cone opened on  
the north-west side--the cleavage being 
manifest by a line of fumaroles--and a  
lava stream issued from the lowest part 
without any noise and with very little  
smoke1 and poured down into the ,atria  
del ,cavallo as far as the precipices of

 ,monte di ,somma4 ,this lava ceased    
flowing after a week1 but the fumaroles 
pointed out the cleft of the cone2 and  
between the small re-made cone1 which   
had risen to the height of #ce metres1  
and the central crater1 a new crater of 
small dimensions and interrupted        
activity opened4  ,on the #bcrd ,april  
7another full moon7 the ,observatory    
instruments became agitated1 the        
activity of the craters increased1 and  
on the evening of the #bdth splendid    
lavas descended the cone in various     
directions1 attracting on the same night
 the visits of a great many strangers4  
,all these lava streams were nearly     
exhausted on the morning of the #beth2  
only one remained1 which issued from the
 base of the cone1 not far from the spot
 whence that of the preceding month had 
issued4 ,numbers of visitors1 attracted 
by the splendour of the lava streams of 
the preceding night1 which they supposed
 still continued1 soon arrived1 but1    
finding them exhausted1 were for the    

most part conducted by their guides to  
see the one still flowing4 ,it was      
almost inaccessible1 and to reach it one
 had to walk over the rough inequalities
 of the scori4 ,it took me two hours to 
get there from the ,observatory1 when ,i
 visited it that morning1 and therefore 
,i endeavoured to dissuade those who    
wished to visit it at night from the    
attempt1 but set out myself from the    
,observatory at #g p4m41 leaving my only
 assistant there4 ,the instruments were 
agitated4 ,after midnight the           
,observatory was closed1 and my         
assistant retired to rest4 ,late and    
unlucky visitors passed unobserved with 
an escort of inexperienced guides2 at   
half-past #c o'clock in the morning of  
the #bfth they were in the ,atria del   
,cavallo1 when the ,vesuvian cone became
 rent in a north-westerly direction1 the
 fissure commencing at the little cone  
which disappeared1 and extending to the 
,atria del ,cavallo1 whence a copious   
torrent of lava issued4 ,two large      

craters formed at the summit of the     
mountain1 discharging numerous          
incandescent projectiles with white     
ashes1 and glittering with particles of 
mica1 which frequently recurred4  ,a    
cloud of smoke enveloped these          
unfortunates1 who were under a hail of  
burning projectiles and close to the    
lava torrent4 ,some were buried beneath 
it,b and disappeared for ever2 two dead 
bodies were picked up1 and eleven       
grievously injured1 one of whom died    
close to the ,observatory4 ,he alone    
revealed his name1 ,antonio ,giannone4  
,i learned afterwards that he was a fine
 young fellow1 and ,assistant-,professor
 in one of the ,universities4           
,assistant-,professors ,signor ,franco1 
who is a priest1 and ,signor ,francesco 
,cozzolino1 a priest also1 entrusted    
with the festive mass for the           
,observatory1 hastened to assist the    
dying4 ,on my own return thither1 the   
sad spectacle of the dead and dying     
awaited me2 the former were conveyed1   

through the assistance of the municipal 
officer of ,resina1 to the ,cemetery1   
and the latter to the ,hospital4 ,but we
 must leave this scene of grief and     
sorrow1 and return to the eruption4     
,the fissure of the cone on the         
north-west side was large and deep1 and 
extended into the ,atria del ,cavallo1  
about #cjj metres4 ,no mouth opened     
along the cleft of the cone itself2 all 
the lava issued from that part which    
extended into the ,atria4 ,from previous
 experience ,i should have expected to  
have seen the formation of adventitious 
cones along the widest part of the      
fissure1 which is never that most       
elevated1 and these discharging from    
their summits riform matter frequently  
mixed with projectiles1 and from their  
base lava2 but on this occasion no cone 
appeared at the widest part of the      
fissure1 but a long hillock was formed  
like a little chain of mountains1 one   
point of which was elevated about fifty 
metres above the plain beneath1 and     

bearing no resemblance to a cone4       
,another fissure opened in the cone on  
the south side1 which did not extend to 
the base1 and lava issued from this and 
flowed in the direction of the          
,camaldoli4 ,streams of less importance 
furrowed the cone in other directions1  
but the largest quantity of lava        
proceeded from the fissure in the ,atria
 del ,cavallo1 below the hillock or     
miniature chain of collines just        
described4 ,this lava stream was for    
some time restrained within the ,atria  
del ,cavallo1 among the holes and       
inequalities of the lavas of #ahga1 but 
these being filled up and overcome1 it  
divided into two branches--the smaller  
one flowing through a hollow which      
separated the lavas of #ahfg from those 
of #ahga1 and made its way over the     
lavas of #aheh1 threatening ,resina1 but
 stopped as soon as it reached the first
 cultivated ground2 the larger branch   
precipitated itself into the ,fossa     
della ,vetrana1 occupying the whole     

width1 about #hjj metres2 and traversing
 the entire length of #a1cjj metres in  
three hours4 ,it dashed into the ,fossa 
di ,faraone2 here it again divided into 
two streams1 one overlying the lava of  
#ahfh1 on the ,plain of the ,novelle1   
partially covering the cultivated ground
 and country-houses2 the other flowing  
on through the ,fossa di ,faraglione1   
over the lava of #ahee1 reached the     
villages of ,massa and ,st4 ,sebastiano1
 covering a portion of the houses1 and  
thence continued its course through the 
bed of a foss or trench which1 contrary 
to my advice1 had been excavated after  
the eruption of #ahee1 in the           
expectation of diverting the course of  
that lava4 ,i did not fail to observe   
that the rains which previously         
descended through these steep channels1 
would in future be kept back to filtrate
 through the scori1 without ever        
reaching the new channel4  ,the lava of 
this eruption1 meeting with this said   
excavation1 flowed into it1 instead of  

pursuing its road over the lava of      
#ahee1 and thus invaded highly          
cultivated ground and towns of          
considerable value1 extending to the    
very walls of a country-house belonging 
to the celebrated painter1 ,luca        
,giordano4 ,this lava stream1 having    
surmounted the obstacles which the heaps
 of scori in the ,atria del ,cavallo    
presented to it1 ran with great velocity
 7notwithstanding its being greatly     
widened out in the ,fossa del ,vetrano71
 so that between #aj a4m4 and #aa p4m4  
it traversed about five kilometres of   
road1 occupying a surface of five to six
 square kilometres4 ,if it had not      
greatly slackened after midnight1 from  
the failure of supply at its source1 in 
twenty-four hours more1 by occupying    
,ponticelli1 it would have reached      
,naples1 and flowed into the sea4       
,although ,i had often visited the two  
villages of ,massa and ,st4 ,sebastiano1
 previously greatly injured by the lava 
of #ahee1 yet ,i could not well         

estimate1 upon now seeing them again1   
the number of houses which had          
disappeared4 ,massa seemed to me        
diminished by about one-third1 and ,st4 
,sebastiano by somewhat less than a     
fourth4 ,but the way of escape was open 
to the inhabitants of ,massa2 whilst a  
great river of lava occupying the road  
leading to ,st4 ,giorgio a ,cremano     
would have hindered the flight of the   
inhabitants of ,st4 ,sebastiano1 if they
 had been dilatory4 ,the lava stream now
 separating the two villages is little  
less than a kilometre in width1 and is  
about six metres in height4  ,on the    
night of the #bfth ,april1 the          
,observatory lay between two torrents of
 fire1 which emitted an insufferable    
heat4 ,the glass in the window-frames1  
especially on the ,vetrana side1 was hot
 and cracking1 and a smell of scorching 
was perceptible in the rooms4 ,the cone1
 besides being furrowed by the lava     
streams just described1 was traversed by
 several others1 which appeared and     

disappeared4 ,it seemed completely      
perforated1 and the lava oozed as it    
were through its whole surface4 ,i      
cannot better express this phenomenon1  
than by saying that ,vesuvius sweated   
fire4 ,in the day-time1 the cone        
appeared momentarily covered with white 
steam jets 7fumaroles71 which looked    
like flakes of cotton against the dark  
mountain-side1 appearing and            
disappearing at brief intervals4        
,simultaneously with the grand fissure  
of the cone1 two large craters opened at
 the summit1 discharging with a dreadful
 noise1 audible at a great distance1 an 
immense cloud of smoke and ashes with   
bombs and flakes1 rising to the height  
of #acjj metres,c above the brim of lava
 7sull' orlo de essi74 ,the white ashes1
 before described1 although they did not
 fall beyond the ,crocella1 were carried
 by the wind as far as ,cosenza1 from   
whence they were sent to me by ,dr4     
,conti4 ,these ejections were followed  
by dark sand1 with lapilli and small    

fragments of scori of the same colour4  
,the smoke1 driven up with violence1    
assumed the usual aspect of a pine tree1
 of so sad a colour that it reminded us 
of the shadowy elm of ,virgil's dreams  
7ulmus opaca ingens74 ,from the trunk   
and branches of the pine-tree cloud fell
 a rain of incandescent material1 which 
frequently covered all the cone4 ,the   
lapilli and the ashes were carried to   
greater distances4  ,the victims of the 
morning of the #bfth1 the torrents of   
fire which threatened ,resina1 ,bosco   
and ,torre ,annunziata1 and which       
devastated the fertile country of the   
,novelle1 of ,massa1 ,st4 ,sebastiano   
and ,cercola1 the two partially buried  
villages1 the continual and threatening 
growlings of the craters1 caused such   
terror that numbers fled from their     
dwellings near the mountain into        
,naples1 and several in ,naples went to 
,rome or to other places4 ,very many    
delayed from the knowledge that ,i was  
in the ,observatory1 and held themselves

 in readiness for flight whenever ,i    
should abandon it4  ,the rapidity with  
which the vast torrent of fire assailed 
the houses 7i4e41 in these villages71   
and the great heat which spread to a    
distance1 scarcely allowed the fugitives
 to carry away any of their belongings2 
many were completely destitute4 ,the    
authorities vied with each other in     
zealous efforts to relieve the distress1
 and the municipality of ,naples        
sheltered and fed the wretched beings   
for many days4  ,the igneous period of  
the eruption was short1 for on the      
morning of the #bgth the lava stream1   
bearing down upon ,resina1 having       
covered a few cultivated fields1        
stopped2 the lava descending from the   
summit of the mountain towards the      
,camaldoli also stopped2 and the great  
lava torrent1 which passed the shoulders
 of the ,observatory through the ,fossa 
della ,vetrana1 lowered the level of its
 surface below those of its two sides1  
which appeared like two parallel        

ramparts above it4  ,if these streams   
had continued on the #bgth1 flowing in  
the same manner as they did on the night
 of the #bfth1 they would have reached  
the sea1 bringing destruction to the    
very walls of ,naples4  ,but before     
leaving the subject of these lavas ,i   
must narrate an important fact to which 
,i was witness1 and which was thrice    
repeated1 near the banks of the great   
river of fire that ran close to the     
,observatory4 ,at three several points1 
and at different times1 ,i observed     
great balls of black smoke issue from   
the lava1 driven up with continued      
violence1 as if from a crater2 through  
the smoke ,i frequently observed        
numerous projectiles thrown up into the 
air1 but ,i could not say whether with  
noise or in silence1 for the noise of   
the central crater was deafening4 ,each 
of these little eruptions1 which ,i may 
call external eruptions1 lasted from    
fifteen to twenty minutes4 ,the first   
took place at the most elevated point of

 the ,fossa della ,vetrana1 on the right
 bank of the torrent2 the second1 under 
the hill of ,apicella1 where the lava   
divided into the two branches1 before   
described2 and the third near to the    
,observatory on the left bank of the    
lava stream4 ,these singular explosions 
terminated without leaving little cones 
or craters1 the lava in its impetuosity 
carrying every trace away4 ,these       
eruptions were seen from ,naples1 and   
the ,observatory was justly believed to 
be in danger4 ,one has been clearly     
photographed1 the one which was the best
 seen from ,naples1 being the nearest   
and the least darkened by the smoke of  
the lava4 7,plate #d47 ,is this the     
first time that the phenomenon has been 
remarked8 ,i believe that it is at least
 the first time it has been             
authenticated4 ,the authority of ,julius
 ,schmidt1 quoted by ,scrope1 has no    
weight with me1 for ,i was also a       
witness of what happened at ,vesuvius in
 #ahee2 and1 although these cones were  

in the midst of the lava in the ,atria  
del ,cavallo1 they originated1 according
 to the opinion of everyone1 from the   
fissure from which the other and much   
larger cones proceeded4 ,the same       
phenomenon was observed in the ,atria   
del ,cavallo in #aheh1 when ,i caused   
two of the little cones to be brought to
 the ,observatory2 but these also might 
belong to the fissure along which the   
other cones were arranged4 ,the same may
 be said of the little craters observed1
 after they had been exhausted1 by      
,professor ,scacchi in #ahej4 ,but the  
discharging mouths now observed in the  
,fossa della ,vetrana1 which existed for
 twenty minutes and then disappeared1   
and which were not at all in a          
continuous line1 and could not be       
supposed to correspond with any fissure 
beneath1 constitute a circumstance      
which1 if not new1 is evident for the   
first time1 and cause the recognition of
 a power in the lava itself to form     
eruptive fumaroles4#b  ,the igneous     

period of the eruption having terminated
 on the evening of the #bgth1 the ashes1
 lapilli1 and projectiles became a      
little more abundant1 whilst the roaring
 noises of the craters apparently became
 greater4 ,the pine-tree cloud was of a 
darker colour1 and was furrowed by      
continual lightning1 visible by daylight
 from the ,observatory4 ,many writers on
 the subject of ,vesuvius affirm that   
the flashes which appear through the    
smoke cloud were lightning unaccompanied
 with thunder1 but they studied the     
phenomena from ,naples1 or some place   
more or less distant from the crater1   
where the report of the thunder was     
inaudible1 or could not be distinguished
 from the bellowing and detonation of   
the mountain4 ,the fact is that these   
flashes were constantly followed by     
thunder1 after an interval of about     
seven seconds4,d ,when the flash was    
very short1 a simple noise like the     
report of a gun was heard1 but if it    
were long1 a protracted sound like that 

from torn paper ensued4  ,on the #bhth  
the ashes and lapilli1 continuing to    
fall abundantly1 darkened the air1 yet  
without diminishing the terrible noise2 
at ,resina1 ,portici1 ,st4 ,giorgio a   
,cremano1 ,naples1 etc41 terror was     
universal4  ,on the #bith1 with a strong
 wind blowing from the east1 scori of   
such a size fell at the ,observatory1   
that the glass of the windows           
unprotected by external blinds was      
broken4 ,the noise from the crater      
continued1 but the projectiles rose to a
 less height1 indicating a diminution in
 the dynamic power of the eruption4     
,towards midnight the noise of the      
craters was no longer continuous1 and   
recurred with less force and for shorter
 intervals4 ,almost at the same hour a  
tempest burst over the ,campania with   
loud thunder and a little rain4 ,the    
grass1 the seeds1 the vine tendrils1 the
 leaves and tops of the trees dried up  
immediately1 and the country was changed
 from spring to winter4 ,the storm1     

although repeated on the following days1
 passed away by degrees1 and thus the   
floods1 which ,i strongly feared1 did   
not occur4 ,almost always after great   
eruptions of ,vesuvius1 storms of heavy 
rain have followed1 and the ground being
 covered with ashes1 the water could not
 filtrate through into the soil1 but    
descended in muddy torrents over the    
adjacent country1 occasioning as much   
damage as the fire itself4  ,on the     
#cjth1 the detonations were very few1   
and the smoke issued only at intervals1 
and by the #ast ,may the eruption was   
completely over4  ,when the smoke had   
cleared off the figure of the cone was  
seen to be changed4 7,vide ,plate #e;a47
  ,the ground was perpetually disturbed 
whilst the ,volcano raged1 so that the  
,observatory oscillated continually4    
,some shocks were felt not only in the  
adjacent territory1 but at a greater    
distance1 at ,montovi and elsewhere4    
,the oscillations at the ,observatory   
were chiefly undulatory1 from ,n4,e4 to 

,s4,w4 ,they were observed for some days
 after the termination of the eruption1 
but not continuously1 although they     
maintained some intensity4  ,if we refer
 to ,january1 #ahga1 we shall find that 
that eruption was preceded by several   
earthquakes1 among which were those of  
the months of ,october1 ,november and   
,december1 in the previous year1 that   
wrought such destruction in ,calabria1  
and especially in the province of       
,cosenza2 if we consider that as only   
the last phase1 we shall find that it   
was preceded by great shocks of         
earthquake that devastated some regions 
of ,greece4#c  ,the great quantity of   
lapilli which fell buried the scori with
 which the ,vesuvius cone was covered1  
so that it became somewhat more         
difficult to ascend to the summit1 and  
much less difficult to descend4 ,having 
reached the top of the mountain1 ,i     
found a large crater divided into two   
parts by what seemed a cyclopean wall4  
,the two abysses had vertical sides1 and

 revealed the internal structure of the 
cone4 ,their vertical depth was #bej    
metres2 and beyond that ,i observed a   
sort of tunnel perforated in the rock1  
with a covering arch raised above the   
bottom of the eastern abyss about #ab   
metres1 judging by the eye4 ,the        
interior walls of the crater showed     
neither the usual stalactitic scori nor 
sublimations1 nor fumaroles1 but        
alternate beds of scori and of compact  
lava4 ,the fumaroles and sublimations   
abounded1 only about the brims of the   
craters4 ,hydrochloric and sulphuric    
acid and sometimes sulphuretted hydrogen
 affected respiration1 and the          
temperature rose sometimes to #aej      
degrees4 ,various fissures about the    
brim of the double crater indicated     
prolongations downwards1 which allowed  
me to descend with a rope1 in order to  
examine the interior of the tunnel to   
which ,i have just alluded4 ,the highest
 brim of the crater was fissured for a  
distance of #hj metres1 and the greatest

 depth of fissure was at that place4    
,by measurement with the barometer1 we  
ascertained approximately 7for only one 
barometer was used7 that the height of  
the ,vesuvian cone was somewhat         
diminished4  ,not only the ,vesuvian    
cone1 but the whole adjacent country    
appeared white for many days1 as if     
covered with snow1 when exposed to      
sunlight4 ,this was due to the sea-salt 
contained in the ashes with which the   
surface was strewn4  ,a great quantity  
of coleoptera assembled on the flat roof
 of the ,observatory1 where the ashes   
and lapilli were heaped up two          
decimetres in height4 ,i found the same 
species on the cone1 where many insects 
were observed on other occasions1 such  
as the ,cuccinella septempunctata2 the  
crysomela populi1 etc41 were wanting4   
,this phenomenon of the extraordinary   
concourse of insects on the top of      
,vesuvius1 in order to die in some of   
the fumaroles1 especially noted previous
 to and after great eruptions1 is a     

circumstance for which ,i cannot        
account4#d ,the whole of the lava       
emitted in this eruption occupies a     
surface of about five square kilometres2
 allowing an average thickness of four  
metres1 we obtain a mass of twenty      
millions of cubic metres4 ,about        
three-fifths of this lava did no injury1
 being deposited upon other pre-existing
 lava4 ,however1 the lava in the        
,novelle1 which was deposited upon the  
lava of #aheh1 covered quarries of the  
best stone which had been worked at the 
time1 covered many paths that had been  
cleared1 and buried the new ,church of  
,st4 ,michele1 with some houses that    
surrounded it1 which had been rebuilt on
 the site of the former church1 which   
was covered by the lava of #ahfh4 ,the  
destruction of land in occupation1 of   
buildings and of crops1 exceeded three  
million francs in value4 ,many proposals
 for relieving the sufferers have been  
received4 ,wishing to aid in this       
benevolent work1 ,i gave a public       

lecture1 admission for each person being
 one franc2 and this lecture1 from notes
 badly taken1 was printed by private    
speculation1 and ,i was compelled to    
repudiate the report of it through the  
public papers4  ,the evolutions of      
carbonic acid 7mofette71 which usually  
appear at the end of great ,vesuvian    
eruptions at low-situated spots or      
hollows1 with very rare exceptions1 were
 observed on this occasion a few days   
after the eruption had completely       
ceased4 ,they appeared in the direction 
of ,resina4 ,i found the most elevated  
at ,tironi1 and the most numerous       
between ,la ,favorita and the ,bosco    
,reale di ,portici4  ,the water in wells
 was on this occasion neither deficient 
nor scarce previous to the eruption1 but
 was very acid after the appearance of  
the carbonic acid evolutions in those   
neighbourhoods in which they abounded4  
,having stated that the disastrous      
conflagration of the #bfth ,april ought1
 in my opinion1 to be regarded as the   

last phase of a long period of eruption1
 which commenced at the beginning of    
#ahga1 ,i consider it right to discuss  
the question at somewhat greater length4
  ,not only from twenty years' personal 
observations1 but from the attentive    
study of accounts of previous eruptions1
 ,i have found that when the central    
crater awakens with small eruptions     
after a certain time of previous repose1
 these almost always have a long        
duration1 and1 after various phases of  
increase and decrease1 terminate in a   
great eccentric eruption1 that is to    
say1 with the production of an aperture 
from which a copious lava stream issues4
 ,the eruptions of #aheh1 #ahfa1 #ahfh  
and #ahgb1 furnish the most recent      
examples of what ,i affirm4 ,i might    
cite many others of earlier date1 but ,i
 shall content myself with recording the
 greatest conflagration of this century1
 that of ,october1 #ahbb4  ,before the  
erection of the ,vesuvian ,observatory1 
it was impossible to obtain a           

consecutive account of all the phases   
which the ,volcano presented2 but we    
generally obtained the description of   
the more splendid phases of the eruption
 which arrested the attention of        
everyone4 ,hence1 notices of the small  
phenomena which preceded a great        
eruption are frequently wanting4 ,we    
cannot always ascertain whether the     
fumaroles of the craters became active  
and at what periods1 what was their     
temperature and what the diverse nature 
of their emanations1 etc43 whether and  
when any change in the crater with      
slight eruptive manifestations occurred2
 discharges which sometimes commenced in
 the bottom of a crater becoming active1
 and so are invisible at ,naples4  ,but 
it may be asked whether the inverse     
proposition be equally true1 that is1   
whether all the great eruptions of our  
,volcano were preceded by small fiery   
manifestations of long duration8 ,there 
have undoubtedly been great eruptions   
not preceded by small central eruptions1

 but these also had their period of     
preparation or precursory signs4 ,after 
the great eruption of #ahej1 ,vesuvius  
remained in apparent repose until the   
end of ,may1 #ahee1 when there was an   
eccentric eruption and a great flow of  
lava lasting twenty-seven days4 ,but for
 a year before the fumaroles on the top 
of the mountain had acquired great      
activity1 their temperature increased1  
and hydrochloric and sulphuric acid     
became more abundant1 and generated the 
usual coloured products on the adjacent 
scori4 ,finally1 in the month of        
,january1 a crater was formed by falling
 in of the ground1 and although it did  
not discharge fire1 yet it poured forth 
dense smoke4 ,this was the beginning of 
the fissure manifested four months      
afterwards4  ,ignazio ,sorrentino1 who  
spent a long life in the study of       
,vesuvius1 and frequently ascended it1  
considered the increase of those yellow 
products--which are chiefly chlorides of
 iron1 but were1 at that time1 mistaken 

for sulphur--as the sign of an          
approaching eruption4  ,the only grave  
objection that can be alleged is that of
 the memorable eruption of #afca1 which 
surprised the neighbouring population so
 suddenly that many perished miserably1 
surrounded or covered with lava4 ,but   
that terrible conflagration occurred    
after centuries of repose1 so that trees
 had grown in the interior of the       
crater4 ,no one suspected the           
possibility of danger4 ,it took place1  
too1 at the end of autumn1 when the cone
 is usually covered with clouds1 and1   
therefore1 no one had an opportunity of 
observing any precursory phenomena4     
,when the ,observatory was established1 
,i was able--in the first instance1 at  
my own expense1 and afterwards with some
 slight assistance from ,government--to 
undertake studies more assiduous than   
any previously made4 ,i had two         
instruments adjusted to indicate the    
internal efforts of the ,volcano1 viz41 
,m4 ,lamond's apparatus of variations1  

which1 by means of finely-balanced      
needles and methods of amplification    
proposed by ,gauss1 indicates the       
slightest trepidation of the ground1 and
 my own electro-magnetic seismograph1 a 
self-registering instrument of exquisite
 delicacy4 ,these instruments1 when     
attentively observed1 give the most     
valuable information with respect to the
 activity of the adjacent ,volcano4  ,if
 the very slightest eruption occurs1    
these instruments manifest slight       
perturbation1 increasing with the       
activity of the mountain4 ,when the     
,volcano attains a certain degree of    
activity1 and the instruments are       
proportionately disturbed1 it is        
impossible to foresee a new phase of    
increase without constantly watching the
 changes in the intensity of the        
perturbations2 and to effect this it is 
requisite to have upon the spot a staff 
of assistants sufficiently numerous1    
scientific and intelligent4 ,if1        
therefore1 on the night preceding the   

#bfth of ,april the instruments had been
 properly watched1 they would have      
undoubtedly indicated the great increase
 in the activity of the ,volcano4 ,the  
perturbations on the #bcrd were steadily
 increasing1 and on the evening of the  
#beth they were much stronger than on   
the #bdth1 but on the morning of the    
#bfth they had become extraordinarily   
strong2 they must1 therefore1 have      
increased considerably during the night4
     ,,ii4  ,,nature ,,of ,,the ,,lavas4
   ,when the observer is near the source
 of the lava1 he sees matter in a state 
of fusion1 which1 like a torrent of     
liquid fire1 runs along1 with more or   
less impetuosity1 between two banks     
formed by itself4 ,but as soon as the   
surface of the torrent cools to the     
point of congelation1 it loses the      
splendour of its first incandescence4   
,the part which begins to harden breaks 
readily in some lavas into fragments    
which float on the viscous fluid        
beneath2 these1 increasing in number    

with distance from the source1 conceal  
the molten matter beneath and retard its
 progress1 and at last nothing is seen  
but the more or less red-hot scori      
moving along4 ,these lavas ,i shall call
 ,lavas with fragmentary scori4  ,on    
other occasions1 a skin forms on the    
surface of the lava1 which1 gradually   
thickening1 keeps flexible for some     
time1 and then wrinkles or swells or    
extends and breaks to give egress to the
 hot fluid within1 which1 in its turn1  
skins over and repeats the same         
phenomena4 ,this ,i shall call ,lavas   
with a united surface4  ,these1 in their
 course1 discharge less smoke than the  
first1 draw out more easily into        
threads1 and1 when cold1 have a dark    
colour1 something like bitumen or pitch4
 ,the lava with fragmentary scori1 when 
stretched1 breaks easily1 discharges    
smoke copiously1 and1 when hardened1 has
 a more bluish tint1 like clods of      
upturned earth 7formato di zolle74 ,it  
is noisy in its course1 because the     

incoherent scori that it carries along  
strike and crunch against each other2   
the other lava flows silently1 except   
for a sort of crackling arising from the
 actual fracturing up of the solid skin 
by distension from the liquid matter    
within4 ,if required to give the        
mineralogical characteristics of this   
lava1 ,i would say that it was rich in  
leucite and contained little or no      
pyroxene2 the fragmentary lava1 on the  
contrary1 is poor in leucite and rich in
 pyroxene4 ,the lavas of #ahga were of  
the united surface character2 those of  
#ahgb were fragmentary1 with some       
characteristics which ,i shall describe3
       #a4 ,they were of the clearest   
tint ,i have ever seen1 when            
regarded superficially1 but1 when       
broken1 the fracture was      darker    
than any other lava4       #b4 ,they had
 very little leucite and abounded in    
pyroxene and      olivine1 and sometimes
 contained a few crystals of amphibole4 
#c4 ,their specific gravity varied with 

their porosity2 the most      compact   
attained #bge4       #d4 ,these lavas   
carried along in their course a quantity
 of      scori which had long been      
subjected to the action of the acids    
of the fumaroles close to the craters1  
and also a great many      bombs        
7bombe7--that is1 round masses similar  
to those ejected      from craters4     
,these varied in size1 some having a    
diameter of      four to five meters4   
,they frequently contained a large      
nucleus      of very leucitic lava1 like
 that of #ahga1 with a larger or        
smaller quantity of feroligiste         
7peroxide of iron74 ,others             
contained lavas changed by the action of
 the acid vapours near      the craters4
 ,these bombs must have flowed out with 
the lava1      for they are found       
through its whole course1 and they were 
certainly not ejected from the crater2  
for not only are they      found on the 
lava exclusively1 but masses so enormous
 were not      thrown up from the       

craters during the eruption2 those lying
 on      the cone near the craters      
seldom exceed a decimetre in            
diameter4  ,as to the qualitative       
chemical analysis of the lavas1 it      
always presents the same elements1 with 
the exception of small quantities of    
some metals1 lead for example1 which    
have escaped the researches of good     
chemists1 but which ,i have constantly  
found in the sublimations of the        
fumaroles of the lava4 ,with respect to 
the quantitative analysis1 two specimens
 of the same lava appear indeed to have 
their constituents in different         
proportions4 ,to arrive at any          
conclusion a long and patient           
investigation1 requiring means and      
assistance which the ,observatory does  
not possess1 would be necessary4        
,professor ,fuchs1 of ,heidelberg1 has  
devoted himself to this work for years  
past1 and if he continue it with        
well-selected and sufficiently large    
specimens we may hope some day to obtain

 satisfactory results4       #e4 ,every 
specimen of lava which ,i examined with 
a very      sensitive magnetoscope      
improved by myself1 was invariably      
magneto-polar1 not excepting the pieces 
of the bombs1 whether      rejected from
 the crater or carried along with the   
lava4     ,,iii4  ,,fumaroles ,,of ,,the
 ,,lavas4   ,smoke generally issues from
 all lava when it cools down to a       
certain degree1 hence it is more        
abundant at the edges of the fiery      
torrent1 or is liberated from the scori 
that form on its surface4 ,but when the 
lava stops1 the smoke issues only from  
certain vent-holes1 through which we can
 still see the fire1 and at the edge of 
which different amorphous or            
crystallized matters collect by         
sublimation4 ,these centres of heat1 of 
more or less duration1 are the fumaroles
 of the lavas4 ,i believe ,i have on    
other occasions shown that a fumarole is
 nothing but a communication between the
 more or less cooled and hardened       

surface of the lava and the interior1   
which is still incandescent4 ,some      
fumaroles last but a day1 others        
preserve their activity for weeks1      
months or years1 according to the depth 
of lava through which they penetrate2   
and when they cease to be active1 that  
is1 when the sublimations are formed1 or
 smoke or other riform matters issue    
from them1 they still retain a rather   
elevated temperature4 ,in the lavas of  
#aheh1 in a place where they had a      
transverse width of #aej metres1 a      
vent-hole may still be found where the  
thermometer registers #fj and the scori 
are warm4 ,sometimes1 while the lava is 
in process of cooling1 new fumaroles    
appear1 in which the fire is visible4   
,this phenomenon1 which appeared        
marvellous and inexplicable when ,i     
first observed it in #ahee1 is now very 
easily understood2 the cooled and       
hardened crust of the lava fractures    
with noise and suddenly1 and so a new   
communication is opened with the        

incandescent lava below1 thus creating a
 new fumarole4  ,as the smoke of the    
fluid lava is perfectly neutral1 that   
is1 neither acid nor alkaline1 so the   
fumaroles at the first period of their  
existence with sublimations of sea-salt1
 mixed frequently with oxide of copper  
either in black powder or in shining    
lamin1 ought also to be neutral4 ,but if
 the fumarole continues active1         
hydrochloric acid issues with the smoke1
 and often some time after sulphuric    
acid4 ,then the sublimations turn first 
yellow1 then green1 and more rarely     
azure4 ,the chemical reactions show that
 these sublimations are chlorides or    
sulpho-chlorides1 and sometimes         
sulphides1 and they afford reactions1   
indicative of soda1 magnesia1 copper1   
lead1 and traces of other substances1   
not excluding ammonia1 which ,i must    
speak of separately4 ,this1 ,i have     
observed1 is the general law with the   
fumaroles of the tranquil lavas1 which  
occur with long and moderate            

eruptions--for instance1 the lavas of   
#ahga1 and even those of #ahgb1         
preceding the #bfth ,april4  ,but in the
 great lavas of the great conflagrations
 of ,vesuvius1 chloride of iron more or 
less in combination with all the other  
substances above mentioned changes the  
appearance of the sublimations4 ,the    
fumaroles in the lava of the #bfth      
,april frequently indicated chloride of 
iron4 ,sulphuretted hydrogen1 by        
reaction of sulphurous acid1 is         
decomposed1 and sulphur sublimed1 having
 a particular aspect1 collects on the   
scori4 ,this is never found but in      
fumaroles of the smaller lavas2 it was  
therefore absent in those of #ahga1 but 
frequently occurred in those of #ahgb4  
,although the sublimations are generally
 mixtures1 yet sometimes distinct and   
crystallized chemical or mineral species
 are found1 such as sulphur1 sal        
ammoniac1 tenorite1 cotunuite1 etc4     
,micaceous peroxide of iron             
7feroligiste71 so common near eruptive  

cones1 is very scarce on lava2 any found
 in it has been carried down from the   
craters1 and proofs of this transport   
are very abundant and striking in the   
lavas of this last eruption4 ,even the  
iron found in the bombs is evidently    
transported2 there is a fumarole on the 
ridge of the lava in the ,fossa di      
,faraone which contains micaceous       
peroxide of iron1 and this1 at first    
sight1 appears to oppose what ,i have   
affirmed2 nevertheless1 it gives        
additional force to my statement4 ,this 
fumarole is only a bomb or rounded mass 
of enormous size1 four or five metres in
 diameter4 ,smoke and hydrochloric acid 
issued from the aperture in its         
envelope1 and being partly broken it was
 seen to contain lapilli and pieces of  
antecedent lava1 covered with micaceous 
peroxide of iron4 ,the internal         
temperature of this mass was very high2 
the hydrochloric acid which it          
discharged had1 in some places1 covered 
the micaceous iron with a yellow coating

 of chloride of iron4 ,from small       
apertures1 on the lower side of the     
mass1 white and green stalactites of    
chloride of calcium were visible4 ,in   
one spot only of lava ,i found a        
fumarole1 with a small quantity of      
micaceous peroxide of iron1 evidently in
 a state of formation2 but this was the 
very spot where the lava became         
eruptive1 and whence issued the column  
of smoke which was so well              
photographed--the place under the hill  
of ,apicella4 7,see ,plate #d;a47  ,i   
have enumerated the products which are  
constantly collected in fumaroles1      
although they are not all found at the  
same time or place1 in order to show    
that the sublimations follow a certain  
law in their appearance4 ,tenorite1 for 
instance1 was formerly considered an    
accidental product of certain eruptions1
 and ,i have always found it2 but if you
 visit the fumarole when the acids have 
had time to transform it1 you will no   
longer see it4 ,i found the crystallized

 chloride of lead1 or cotunuite1 as it  
is called1 for the first time in the    
lavas of #ahee1 and thought it a        
singular circumstance2 but from that    
time ,i recognised it in all the lavas1 
though not always so beautiful and      
abundant2 and even when not found as a  
distinct substance1 ,i observed it in   
combination with chloride of copper4 ,in
 the lavas of the #bfth ,april cotunuite
 and tenorite,e were not very abundant1 
because the chloride of iron disturbed  
the greater number of the sublimations4 
,i found sal ammoniac very abundantly on
 the fumaroles of the lavas that invaded
 the cultivated ground4 ,although       
chloride of ammonia1 contrary to        
opinion1 was not wanting in the         
sublimations of the fumaroles of the    
lavas deposited on other lavas1 yet it  
was neither abundant nor crystallized1  
but combined in small quantities with   
other substances4 ,it appeared in great 
abundance in all the fumaroles of lavas 
which covered cultivated or woody       

ground4 ,at first it was scarce enough1 
and mixed with chloride of sodium2 but  
when the rains came the sea-salt was    
washed away1 and sal ammoniac formed    
beautiful crystals1 nearly free from    
adventitious matters1 as was the case   
with the fumaroles of the last lava4    
,afterwards1 when chloride of iron was  
produced1 ferro-chloride of ammonia was 
found4 ,crystals of sal ammoniac were   
sometimes found of a beautiful amber    
yellow4 ,this colour was1 in the opinion
 of my colleague1 ,professor ,scacchi1  
produced by such small traces of        
chloride of iron that neither ,professor
 ,guiscardi nor ,i1 nor indeed any other
 chemists to whom ,i submitted specimens
 for examination1 could detect any4     
,what ,i can affirm with certainty is1  
that these limpid crystals of a yellow  
colour were almost always attached to an
 amorphous substance1 soluble in water1 
composed of various chlorides1 in which 
iron was often detected4  ,from these   
remarks1 it is evident that in the      

tranquil lavas the sublimations appear  
with a certain order of succession1 and 
in the violent lavas1 and those which   
flow most copiously1 they are more      
complicated1 and render both chemical   
analysis and spectroscopic researches   
more difficult4 ,notwithstanding1 ,i    
observed traces of lithium and thallium1
 which ,i had previously perceived in   
some sublimations of #ahga4 ,i purpose  
submitting many sublimations which ,i   
have collected to more complete         
spectroscopic investigation1 although ,i
 am persuaded that the discovery of     
traces of certain bodies in the         
sublimations or in the lavas is a matter
 of small importance to the science of  
volcanoes4 ,i must say1 however1 that   
calcium was discovered on this occasion 
in great abundance1 not only by the     
spectroscope1 but also by chemical      
analysis4 ,sulphate of lime has often   
been found in larger or smaller         
proportions1 but this was the first time
 ,i had observed chloride of calcium    

both close to the craters1 and also in  
the sublimations of the fumaroles upon  
the lavas4 ,the white stalactites which 
,i collected beneath the great mass or  
bomb above described were almost        
exclusively composed of chloride of     
calcium1 and only a few green drops     
manifested1 with the usual re-agents1   
the presence of iron4  ,i did not fail  
to look often at the spectrum of the    
flowing lavas covered with the smoke    
which issued from them1 but ,i always   
had a continuous spectrum4 ,the         
spectroscope employed was ,hoffmann's   
construction1 with direct vision2 but ,i
 think it would be better on other      
occasions to use a spectroscope combined
 with a telescope1 like those used by   
astronomers4  ,but avoiding minute      
particulars of these sublimates1 let us 
see what is the general direction and   
the order of their appearance4          
,sublimations are generally oxides1     
chlorides and sulphates1 sometimes      
sulphides4 ,among the oxides1 we must   

enumerate in the first place tenorite   
and feroligiste or micaceous peroxide of
 iron4 ,the first is almost always found
 at the commencement of activity in the 
fumaroles1 simultaneously with the      
sublimation of chloride of sodium2 the  
second--which is1 perhaps1 never wanting
 in eruptive cones that are often found 
lined with it inside--is seldom         
generated in the fumaroles of the lava1 
and therefore it is not easy to define  
the moment of its appearance4 ,sometimes
 one collects micaceous peroxide of iron
 on the lava1 but it is often           
transported there from the mouths of    
eruption1 as happened on this occasion4 
,trustworthy writers are of opinion that
 all the oxides are derived from the    
decomposition of the chlorides1 but ,i  
think ,i have clearly demonstrated that1
 with regard to copper and lead1 the    
opposite statement may be affirmed2 for 
the oxides are changed into chlorides1  
and hydrochloric acid liberated4 ,oxide 
of copper forms sublimates at the       

beginning1 at the same time as the      
sea-salt2 and if the fumarole be        
anhydrous or1 as ,deville would say1    
dry1 this oxide does not change into    
either a chloride or a sulphate2 but if 
the fumarole gives watery vapour1 after 
a little hydrochloric acid is formed1   
which changes the oxide into a chloride1
 and if whilst this is going on oxide of
 lead be developed1 it is changed into  
the chloride of lead1 so frequently     
found in combination with chloride of   
copper4 ,then the sublimations change   
from white to red or yellow1 and        
specimens when carried away gradually   
turn light blue1 but when heated on     
platinum over a spirit lamp they resume 
their yellow tint4 ,sometimes the yellow
 colour remains longer1 and in time     
changes to green2 this also happens on  
the fumarole itself1 the green          
commencing at the zones furthest removed
 from the centre1 where the temperature 
is highest4 ,when these sublimations are
 greenish1 they become far less soluble 

than at first4 ,the yellow1 so common at
 a certain period on the fumaroles of   
the tranquil lavas1 never attracted     
attention before ,i first examined it1  
doubtless1 because it was considered    
chloride of iron1 and yet in small      
eruptions this is only found close to   
the discharging mouths1 and never in the
 sublimations of the fumaroles of the   
lava2 but1 on the other hand1 it is the 
most copious and common product on the  
lavas of the great eruptions4 ,this     
probably also accounts for the fact that
 lead1 which is so obvious in the       
fumaroles of the lavas1 had never       
previously been observed4 ,in #ahee1 ,i 
noticed the crystallized chloride of    
lead in a fumarole in the ,fossa della  
,vetrana1 and this induced me always to 
look for it on the fumaroles of the     
later lavas2 and ,i ascertained that1 if
 it did not always appear as a distinct 
mineral1 it was easily discovered in    
combination with other chlorides4 ,the  
specimens which ,i have collected are   

not the most beautiful1 but the presence
 of lead in the sublimations is not less
 common4  ,micaceous peroxide of iron1  
when found on the lava1 has been mostly 
conveyed from the eruptive mouths1 as ,i
 have already stated1 and perhaps never 
so abundantly and evidently as on this  
occasion4 ,the lava of the #bfth of     
,april carried along a large quantity of
 round masses or bombs1 varying in size1
 among which were found antecedent lava 
more or less covered with micaceous     
iron1 either collected in the cavities  
of the lava1 or incorporated with its   
mass4 ,sometimes the micaceous iron     
appears like little veins in the paste  
of new lava enveloping the exterior of  
these rounded masses1 an exterior       
compact and lithoidal1 and not          
resembling scori4 ,among these spherical
 masses ,i found one of enormous size1  
four to five metres in diameter1 which1 
having broken up where the exterior     
envelope was thinnest1 ,i found filled  
with a great mass of lapilli and        

fragments of other lavas covered with   
micaceous iron4 ,this bomb still        
preserves 7,june #eth7 an elevated      
temperature within1 and emits smoke and 
hydrochloric acid1 which1 meeting the   
micaceous iron discovered by breaking   
the envelope with blows of a hammer1    
transforms it superficially into        
chloride of iron1 showing most clearly  
how1 on some occasions at least1        
chloride of iron is formed from the     
oxide which precedes it4 ,that those    
lapilli and the pieces of lava were     
solid when enveloped in the paste of the
 new lava1 we infer from seeing the     
impressions on the inside of the said   
envelope4 ,the chloride of calcium1     
which ,i found in this spherical mass   
almost pure1 caused me to suspect that  
the sulphate of lime which is so often  
found on ,vesuvius is a transformation  
of the chloride produced by the contact 
of sulphurous acid1 which easily becomes
 transformed into sulphuric acid4 ,the  
hydrochloric acid which escapes from a  

fumarole coming into contact with the   
scori near its mouth1 produces chloride 
of iron1 which is1 therefore1 not always
 obtained by sublimation1 although1 when
 the temperature is very high1 chloride 
of iron is conveyed from the interior of
 the lava1 and sublimes on the exterior 
and colder parts2 for instance1 the     
chloride of iron which issues from the  
eruptive cones is sometimes found       
sublimed on the rocks of ,monte di      
,somma4 ,when chloride of iron has been 
produced by sublimation1 we may collect 
it inside a glass bell placed over the  
fumarole1 or upon a piece of brick2 but 
when it is produced by the action of    
hydrochloric acid on the scori1 it will 
only be found on the scori themselves4  
,if1 therefore1 the origin of micaceous 
peroxide of iron were due to the        
decomposition of the sesqui-chloride of 
iron requiring a more elevated          
temperature for its decomposition1 it   
would follow that its genesis would be  
easier near the discharging mouths1 and 

more difficult on the lavas1 but there  
the fact was verified3 for example1 in  
the great bomb on the fumarole1 where we
 observed micaceous iron transformed    
into chloride of iron4 ,we may therefore
 consider it proved that some           
chlorides--for instance1 chloride of    
sodium--issue from the lava itself1     
either being there pre-existent1 or     
being formed there2 and that others are 
derived from the oxides which precede   
them1 as undoubtedly is the case with   
chloride of copper2 hence1 the theory   
that derives the oxides always from the 
chlorides cannot be considered true4    
,granting that this theory might be     
applicable to the origin of micaceous   
iron1 we should still want to know how  
it is found with the paste of the new   
lava itself1 which forms the exterior   
coating of the bombs above described4   
,many of these rounded masses1 which    
have been rolled along by the lava1     
contain scori partly decomposed by the  
long action of the acids found on the   

fumaroles of the craters4 ,they         
disintegrate easily1 and have a more or 
less yellowish tint4 ,in the greater    
number of cases the interior of these   
masses is formed of leucitic lava1 with 
cavities lined with micaceous iron4 ,in 
short1 their contents appeared to me    
quite similar to the material of the    
cone of #ahga and #ahgb1 which in all   
probability was engulfed in the large   
crevasse or fissure that opened below   
it2 and the fragments having thus fallen
 down into the lava1 were enveloped by  
it and carried out by it after having   
been more or less rounded4 ,the external
 envelope of these spheres is not at all
 scoriaceous1 but compact and lithoidal1
 and sometimes composed of concentric   
folds or plaits4  ,as to the gaseous    
emanations of fumaroles1 watery vapour  
with few exceptions comes first2 this   
conveys the material which first appears
 in the sublimations1 viz41 sea-salt1   
and for the most part oxide of copper4  
,if the fumarole continue active1 it    

passes from the neutral period to the   
acid period1 and first hydrochloric acid
 is produced1 which1 in small lava      
streams1 never conveys chloride of iron1
 and rarely attacks the scori to form   
that salt1 but expends its force in     
changing the sublimations already there4
 ,for this reason chloride of iron1     
though completely absent in the lavas of
 #ahga1 was abundantly found in those of
 the #bfth ,april1 #ahgb4 ,sulphurous   
acid follows hydrochloric at a later    
period1 and sulphuretted hydrogen       
occasionally succeeds4  ,having examined
 the gases of fumaroles by means of a   
graduated tube1 and the pyrogallate of  
potash1 ,i always found that it         
contained less oxygen than the          
surrounding atmosphere4  ,for several   
years ,i wished to see whether the      
fumaroles of the lavas had a period of  
evolution of carbonic acid1 as sometimes
 happens with fumaroles near the        
craters1 but ,i have always obtained    
negative results4 ,i often found that   

the atmosphere on the lavas contained an
 excess of carbonic acid1 but as these  
lavas had burnt many trees1 and it was  
probable that carbonic acid springs had 
formed under the lava1 ,i never         
considered it safe to form any          
conclusion on the subject4     ,,iv4    
,,bombs1 ,,lapilli ,,and ,,ashes4   ,the
 bombs ejected from the craters are like
 those carried down by the lavas1 but of
 smaller size1 and they seldomer contain
 a nucleus similar to those found in the
 latter4 ,with the bombs properly so    
called1 many pieces of incandescent lava
 were thrown up1 and in their fall went 
beyond the base of the cone4 ,a quantity
 of small scori varying in size         
accompanied these projectiles1 and those
 fragments1 which we call lapilli1 fell 
at a greater distance4 ,with the        
lapilli1 and sometimes without them1 the
 smoke carried a very minute dust or    
sand1 which is generally called ashes4  
,these ashes1 when washed with water1   
lose soluble constituents which they    

have collected in the smoke--such as    
chloride of sodium and other chlorides  
and often free acids4 ,the insoluble    
part originates in the detritus of lava1
 and with the microscope we can detect  
abundant fragments of those crystals    
which most frequently occur in the lava 
of the same eruption4  ,the lavas of    
#ahga1 which were eminently leucitic1   
and almost entirely deprived of         
pyroxene1 resembled the ashes1 which    
appeared to be fragments of crystals of 
leucite1 more or less enveloped in the  
paste of the lava1 so that having       
triturated the scori of the lava1 and   
looked at the powder through the        
microscope1 it was apparently quite the 
same as the ashes4  ,but at the         
beginning of the eruption of the #bfth  
,april1 a white sand fell in the ,atria 
del ,cavallo1 close to the ,crocella#e1 
which on the dark scori of #ahga looked 
like snow4 ,its fall had a limit so well
 defined that one passed without any    
gradation from white to black4 ,having  

collected some of this sand that very   
morning1 ,i put it up in white paper1   
for at that moment it was impossible for
 me to examine it4 ,taking it out some  
days after1 ,i found it had become      
reddish1 and having put it under the    
microscope1 ,i observed that it was     
exclusively formed of little pebbles    
more or less round1 of a transparent    
vitreous matter1 partly covered with a  
red substance4 ,fragments of green      
crystals occurred in this sand1 upon    
which no red was perceptible4 ,i        
consulted our eminent crystallographer1 
,arcangelo ,scacchi1 whether these      
little pebbles were leucite1 as ,i      
suspected1 and whether the green        
particles were pyroxene3 he confirmed my
 suspicion1 and remarked that the red   
colour was superficial only4 ,we then   
washed a little of the sand in hot      
water1 and saw the pebbles become       
whitish2 but having heated some on      
platinum1 we observed that they first   
turned black and then became perfectly  

white1 proving that the red was a       
deposit of organic matter4 ,to see these
 leucites1 rounded like small pebbles   
transported by a torrent1 deprived of   
the soluble chlorides which generally   
accompany ,vesuvian ashes1 is a matter  
worthy of attention4 ,whilst heating    
this sand upon platinum1 decrepitation  
was audible1 which indicated the        
cracking of some of the little pebbles4 
,it is evident1 therefore1 that crystals
 of leucite raised to a certain         
temperature may break1 and thus we can  
understand how almost all ,vesuvian     
ashes contain fragments of the said     
crystals enveloped in the paste of the  
lava4 ,it is evident that the soluble   
part of the ashes is obtained from the  
smoke through which it passes4 ,on this 
occasion the smoke from the craters did 
not apparently contain much acids1 for  
no bad smell was perceptible1 and the   
water in which ,i washed the ashes      
scarcely reddened litmus paper4 ,even   
chloride of iron1 which was so abundant 

in the lavas1 was scarcely perceptible  
in the smoke1 which almost exclusively  
deposited sea-salt on the surrounding   
rocks2 ,i say sea-salt advisedly1 and   
not chloride of sodium1 to show that ,i 
include all that sea-salt contains4 ,the
 slight disturbance it manifested with  
chloride of barium1 and the small       
precipitate with oxalate of ammonia1    
reveal sulphate of lime1 without        
excluding the possibility of the        
chloride4  ,but how can these ashes do  
so much injury to the vegetation of the 
ground they cover1 especially at the    
first fall of rain8 ,i think that the   
damage is due partly to the sea-salt1   
and partly to the acids contained either
 in the ashes or in the rain-water      
itself4 ,upon watering the tender tops  
of some plants with a saturated solution
 of the salt from ,vesuvius itself1 ,i  
noticed that they withered away after a 
few hours4 ,but very often the rain     
alone which traverses the smoke of      
,vesuvius1 or is produced by            

condensation from it1 gives manifest    
acid reactions1 and destroys the grass  
and the tops of the trees4 ,the peasants
 believe that the rain is warm or of    
boiling water1 from observing that the  
tender parts of the plants are1 by its  
deposit1 all burnt up4 ,vegetation is   
now recovering1 but without flowers1 and
 consequently without fruit4     ,v4    
,,the ,,craters ,,and ,,their           
,,fumaroles4   ,the greater part of the 
lava issued from the base of the great  
fissure in the cone which ,i have       
described2 and although two other lava  
streams descended from the top of the   
mountain1 neither proceeded from the    
crater1 but from apertures near it4 ,the
 great crater1 divided in two as already
 described1 opened wide on the morning  
of the #bfth ,april1 destroying the brim
 of the antecedent crater1 and remaking 
it in another shape with ejected matter1
 except on the south-west side1 where   
the brim was split4 7,see ,plate #e47   
,from this double crater1 copious smoke1

 bombs and incandescent scori1 with     
ashes and lapilli1 issued with violence1
 and from the depths below came dreadful
 detonations and bellowings1 producing  
great terror4 ,and yet the lava poured  
out into the ,atria del ,cavallo without
 any noise1 and not even a column of    
smoke marked its origin of              
issue--namely1 from the fissure4  ,when 
the eruption was over1 the sight of the 
vertical walls of these deep craters1 of
 almost horizontal strata of scori and  
lithoidal masses1 with a fracture fresh1
 and as if they had never undergone the 
action of fire or of acid vapours1      
without recent scori and without        
fumaroles1 was to me a marvellous       
spectacle4 ,the fumaroles were almost   
all on the brims of the craters1 with   
emanations of hydrochloric and          
sulphurous acid4 ,in a few that were    
more removed from the brim1 sulphuretted
 hydrogen was perceptible4 ,in the      
sublimations1 chloride of iron was most 
abundant1 in combination with other     

chlorides1 for example1 of sodium1      
magnesium and calcium4 ,this last       
chloride was frequent even among the    
sublimations of the fumaroles of the    
lavas1 and it was the first time it was 
ever remarked1 but ,i do not think it   
was the first time that it was ever     
produced3 being in combination with     
chloride of iron1 and very deliquescent1
 it did not attract attention from      
anyone4 ,in a hollow fragment of scori  
,i observed a yellowish substance1 which
 looked like sulphur in a viscid state1 
and which boiled at a temperature of    
#abj1 and evolved hydrochloric acid4    
,having collected this substance and    
poured it into a glass phial1 it quickly
 coagulated into an amorphous mass of   
the same colour2 but before ,i reached  
the ,observatory1 ,i found that it had  
become liquid by deliquescence4 ,it     
consisted of a mixture of the aforesaid 
chlorides1 according to an analysis made
 by ,professor ,silvestro ,zinno and    
myself4 ,in some fumaroles1 where ,i    

perceived the smell of sulphuretted     
hydrogen1 ,i found sublimed sulphur     
under the scori4  ,at the source of the 
lava stream that flowed towards the     
,camaldoli1 on the seaward flank of     
,vesuvius1 ,i observed large fumaroles  
of steam only1 pure aqueous vapour4     
,there was no trace of carbonic acid in 
these fumaroles1 but that fact does not 
imply that there was none at a later    
period1 for1 since the first            
investigations of ,deville1 it is known 
that carbonic acid is found under       
certain conditions on the very summit of
 ,vesuvius4     ,,vi4  ,,the            
,,electricity ,,of ,,the ,,smoke ,,and  
,,ashes4   ,our ancestors could judge   
that a great amount of electricity was  
occasionally evolved in the smoke1 from 
their observation of the lightning      
flashes that darted through the         
,vesuvian pine tree2 but they had no    
proper instruments for ascertaining     
whether this evolution of electricity   
was constant or accidental1 or what laws

 regulated its manifestations4 ,my      
apparatus1 with movable conductor1 by   
which comparative observations of       
electric meteorology can be made1 and   
the errors arising from dispersion      
corrected1 supplied me with an easy     
method of studying the electricity      
evolved during eruptions4  ,i must begin
 by describing the bifilar electrometer1
 in order to explain the apparatus which
 ,i have named as above1 ,apparechio a  
conduttore mobile4  ,a ,a 7,plate ,v,ia1
 ,fig4 #a7 is a glass cylinder1 the     
lower edge of which is ground1 well     
varnished with gum lac1 and let into a  
wooden base1 ,b1 furnished with three   
levelling screws4 ,through a            
sufficiently wide glass tube1 a a1 runs 
a copper rod covered with insulating    
mastic1 having a little plate or        
cylindrical cavity of gilded brass at   
the top 7,figs4 #b and #c71 with two    
arms d d1 d' d4 ,in the plate a disc of 
aluminium1 m1 is suspended by means of  
two silk fibres1 and to the disc a very 

fine aluminium wire is attached1 f f'1  
bent a little at the ends1 as are the   
arms1 d d1 d' d4 ,the disc has about    
three millimetres less diameter than the
 plate4 ,the diameter of the plate may  
vary within certain limits1 but ,i have 
found it convenient to make it eighteen 
millimetres4 ,the glass tube1 a a 7,fig4
 #a71 should descend below the base as  
much as it rises above it1 that is three
 to four centimetres4 ,the length of the
 index is about one decimetre4  ,the    
upper ends of the two silk fibres1 by   
which the disc and index are suspended1 
are attached to the top of the glass    
tube1 ,c1 by a contrivance which permits
 a change in the distance between the   
two points of suspension1 and a screw1  
p1 is provided to raise and lower the   
disc with the index4 ,at n1 at the lower
 part of the tube1 ,c1 there is a kind  
of torsion micrometer1 arranged so as to
 bring the index to the zero of the     
scale engraved on the graduated ring1   
,b1 which is formed of a strip of good  

paper pasted on the rim of a glass disc4
 ,the index must be placed at the zero  
of the scale1 and must be some distance 
from the ends of the arms of the plate  
with which it is parallel4 ,the plate is
 about three millimetres deep4  ,having 
levelled the instrument1 so as to render
 the disc concentric with the plate1 and
 placed the index at zero1 it is obvious
 that if an electric charge through the 
wire1 h1 reach the plate with the arms1 
it will electrify the disc and index3   
the disc will have the opposite         
electricity1 and the extremities of the 
index will take the same electricity as 
the arms1 and consequently the index    
will describe an arc more or less great4
 ,the motion of the index is            
sufficiently slow to allow the eye      
conveniently to follow it4 ,having      
traversed the first arc1 which ,i call  
the impulsive one1 the index returns1   
and1 after only two oscillations1 comes 
to rest at what ,i shall call the       
definite arc4  ,when the electric       

charges are of very brief duration1 the 
impulsive arcs are within certain limits
 proportional to the tensions1 and the  
ratio between the impulsive and definite
 arcs is expressed by the following     
equation3       ,a 7,b - ,a7 _/ ,b      
tang4 7#a_/b7 ,a  ,in which ,b is the   
impulsive arc and ,a the definite arc1  
showing that ,a comes out nearly equal  
to #a_/b ,b4 ,in dry weather all goes   
perfectly within the limits of          
proportion1 and ,i can tell whether1    
during the time in which the index      
traversed the impulsive arc1 there were 
any dispersions and of what nature2 for 
if the definite arc is not close to the 
limit of the impulsive arc1 it is a sign
 of dispersions having taken place      
during the motions of the index4 ,every 
degree less in the definite arc denotes 
two degrees of loss for the impulsive   
arc2 but as the index employs double the
 time traversing the definite as it does
 the impulsive arc1 we may consider the 
loss of one equal to the loss of the    

other4  ,in excessively damp weather the
 index gives no definite arc1 and it is 
necessary to resort to artificial heat  
in order to dry the insulators4 ,the    
most simple means ,i know of is to hold 
the instrument over some hollow vessel1 
which1 for the time1 is converted into a
 stove by the introduction of a spirit  
lamp4  ,from ,gauss's formula for the   
bifilar system of instruments of this   
class1 we learn that the maximum        
sensitiveness of such instruments is    
given when the length of the suspending 
fibres is greatest1 and the distance    
between them is smallest1 with the      
weight of the movable or rotating member
 a minimum2 and these elements being the
 same1 the sensitiveness of the         
instruments is invariable4  ,to some    
electrometers1 in order to avoid errors 
of parallax1 a small telescope1 with a  
micrometer wire1 has been added2 but1   
with a little practice1 we can read     
accurately without this refinement4 ,in 
order to obtain comparative             

measurements1 it is necessary to select 
some given unit of tension4 ,i have     
observed that by making a galvanic pile 
of copper1 zinc and distilled water1 and
 insulating it well1 each pole has a    
tension which remains the same for many 
days1 if the conditions of temperature  
and the moisture of the surrounding     
atmosphere are not very different4 ,with
 thirty pairs of this pile1 each element
 having twenty-five square centimetres  
of surface1 ,i have on the electrometer 
a definite arc of #ae1 with the         
temperature of the atmosphere at #bj    
,c41 and with the difference of #d to #e
 ,c4 between the thermometers of the    
psychrometer of ,august's construction4 
,the first observation was made         
twenty-four hours after mounting the    
pile4 ,for unit of tension ,i took that 
which corresponded to a single pair1    
that is1 the thirtieth part of the total
 tension4 ,other electrometers may be   
compared with one already properly      
adjusted1 without always having recourse

 to the pile4  ,this done1 let us see   
the arrangement of all the apparatus3   
,h ,h 7,plate ,v,i,ia1 ,fig4 #a7 is the 
ceiling of a well-situated lofty room1  
with an opening1 o o1 at the upper part4
  ,m ,m1 a bracket or table fastened    
against the wall1 about a metre distant 
from the ceiling1 ,h ,h4  ,n ,n1 a      
wooden platform for the observer4  ,a1  
the bifilar electrometer4  ,b1          
,bohnenberger's electroscope4  a a1 a   
movable conductor formed of a brass rod 
#ae to #ah millimetres in diameter1     
insulated below by means of a glass rod1
 well varnished with gum lac1 having a  
suspending pulley1 c1 and a wooden      
guide-rod underneath it1 l1 within the  
guiding tube1 k4 ,at the upper part of  
this conductor1 a a1 there is a sliding 
roof1 b1 which can be adjusted so as to 
prevent rain entering at the opening1 o 
o4 ,the conductor terminates in a disc  
made of a sheet of thin brass1 d1 #bd   
centimetres in diameter4 ,upon this     
disc1 or even in place of it1 we may use

 metallic points4  ,as a support to the 
conductor at the upper part1 ,i have    
made use of a triangular ring1 x1 drawn 
at its full size in ,fig4 #b4 ,the      
conductor passes between three springs1 
and the triangular ring is held in place
 by three silk cords1 m m m4 ,their     
material should not be mixed with any   
cotton1 and it may be advisable to      
saturate them with an alcoholic solution
 of gum lac4  f f f is a hempen cord1   
which is used to raise and lower the    
conductor4  i is a copper wire covered  
with silk1 by means of which the        
triangular ring1 x1 and through that and
 its springs the conductor communicates 
with either the electrometer or the     
electroscope4  ,quickly raising the     
conductor by pulling the cord1 f1 the   
index of the electrometer will describe 
a more or less large impulsive arc1 and1
 after two oscillations1 will stop at   
the definite arc4 ,having thus measured 
the electric tension of the air1 and    
having lowered the conductor1 ,i next   

place the wire1 i1 in communication with
 the electroscope1 ,b1 and by again     
raising the conductor1 ,i ascertain     
whether the electricity be positive or  
negative4 ,it is scarcely necessary to  
say that the conductor1 when raised1    
gives electricity of the same nature as 
that prevailing at the moment in the    
atmosphere2 and when lowered1 manifests 
the opposite4 ,in some conjunctures we  
must keep the conductor raised and in   
communication with the electroscope1 in 
order to observe certain phenomena which
 ,i shall presently describe3 this      
method ,i call observation with a fixed 
conductor4  ,i have also constructed a  
similar but portable apparatus for use  
on eruptive cones1 when required4       
,having given this description of the   
apparatus1 it remains for me to relate  
the results obtained1 especially on the 
occasion of the last eruption of        
,vesuvius4  ,the ,observatory is        
distant1 in a direct line from the      
central crater of ,vesuvius1 #b1chj     

metres1 so that1 when the smoke is      
copious1 it is properly situated for the
 study of electricity1 particularly when
 the wind inclines the pine-tree cloud  
in the direction of the ,observatory1 as
 frequently happened on the last        
occasion4  ,with smoke alone1 without   
ashes1 we obtained strong tensions of   
positive electricity2 with ashes only1  
which sometimes fell while the smoke    
turned in the other direction1 we had   
strong negative electricity2 when the   
smoke inclined towards the ,observatory1
 accompanied with ashes and lapilli1 we 
had sometimes one kind of electricity1  
and sometimes the other1 just as the    
smoke or the ashes predominated2 and    
often with a fixed conductor we obtained
 negative electricity1 and with a       
movable conductor positive electricity4 
,in ,naples1 too1 at the ,meteorological
 ,observatory attached to the           
,university1 my colleague1 ,professor   
,eugenio ,semmola1 observed negative    
electricity of strong tension whilst    

ashes were falling there in abundance4  
,the tensions on this occasion were so  
strong as to equal those obtained at    
changes of weather or during storms     
7temporali71 and1 being beyond measure  
with a delicate electrometer1 we marked 
them with the symbol for infinity3 the  
same phenomena were observed when       
lightnings flashed4  ,when there is but 
little smoke1 it is necessary to        
approach the eruptive mouths with a     
portable apparatus1 in order to observe 
those phenomena which1 in great         
eruptions1 may be studied from the      
,observatory itself4  ,the conditions   
under which 7folgori7 lightning flashes 
are seen from the cloud of smoke are1   
that it is conveying great abundance of 
ashes4 ,in #ahfa1 there were small      
flashes even from the line of eccentric 
mouths above ,torre del ,greco1 although
 the smoke was not very great2 and when 
these ceased to discharge1 and the      
central crater became somewhat active1  
with a moderate amount of smoke but a   

great deal of ashes1 small and frequent 
lightning flashes were observed in the  
twilight darting through the smoke1     
which was dark in colour4 ,in #ahej the 
eruption was more vigorous1 the smoke   
more abundant1 and the ashes scarce1 but
 the flashes were very rare4 ,in #ahee1 
#aheh1 and #ahfh1 with a scanty supply  
of ashes and at intervals1 no flashes   
were observed1 and the electricity      
remained constantly positive4 ,but      
having regard to the facts of antecedent
 eruptions1 one sees that the flashes   
are always derived1 from the midst of   
smoke accompanied with ashes and        
lapilli1 which separate like rain from  
the rolling volumes of smoke1 in the    
midst of which they were ejected4  ,but 
how can we account for the positive     
electricity of the smoke1 and the       
negative electricity of the falling     
ashes8 ,without denying the probability 
that a part of the positive electricity 
depends upon the elevation of the smoke1
 as in the case of every other conductor

 we raise aloft1 or with a jet of water 
sent from a vessel by compressed air1 ,i
 think that the greater part of the     
electricity proceeds from the rapid     
condensation of vapours1 which are      
changed from the gaseous condition into 
dense clouds2 for even when the smoke   
issues tranquilly and does not rise1    
because carried away horizontally by the
 wind1 it gives signs of positive       
electricity4 ,from all my studies of    
atmospheric electricity1 and from some  
experiments made specially1 it follows  
that the condensation of vapours is the 
origin of this development of positive  
electricity4  ,the negative electricity 
of the falling ashes certainly arises   
from the fact itself of their fall2 for 
if we place a metallic vessel full of   
ashes upon an elevated and well-situated
 terrace1 while the atmospheric         
electricity is positive1 and cause the  
ashes from the vessel to fall gradually 
into an insulated metallic cup1         
communicating with ,bohnenberger's      

electroscope placed at three or four    
metres distance from the vessel1 the    
electroscope will manifest negative     
electricity4 ,if the upper vessel be    
insulated1 and the ashes permitted to   
fall upon the ground1 we shall obtain1  
from the vessel1 positive electricity4  
,the intensity of these electric        
manifestations depends 7other things    
being equal7 upon that predominant at   
the moment in the air2 so that if the   
experiment be made while negative       
electricity prevails1 the falling ashes 
will manifest positive electricity1 the 
upper vessel then showing negative      
electricity4 ,now1 as the ashes separate
 from the positively electrified smoke  
in order to approach the ground1 which  
is negatively electrified1 it follows   
that they must manifest negative        
electricity upon touching the ground1   
leaving the positive electricity in the 
smoke above4 ,for this reason1 the      
electric tension of the smoke is        
increased by the descent of the ashes   

and lapilli1 so that discharges between 
the upper and lower part of the         
pine-tree cloud1 or the surface of the  
crater1 are rendered possible4 ,hence it
 follows that the flashes of lightning  
of ,vesuvius play through the smoke1 and
 with difficulty strike bodies upon the 
earth2 and from this circumstance our   
ancestors believed the thunderbolts of  
,vesuvius to be harmless4 ,however1 if  
the smoke were very great1 and driven by
 the force of the wind to some distance 
from the crater1 with an abundant fall  
of ashes1 it would be possible to have  
lightning flashes proceed from the smoke
 to the earth4 ,i possess some documents
 which relate that1 in #afca1           
thunderbolts fell upon the ,church of   
,santa ,maria del ,arco1 and other      
places on the coast of ,sorrento4       
,after upwards of twenty years' study   
and observation of meteoric electricity1
 ,i am enabled to prove that atmospheric
 electricity is never manifested without
 rain1 hail or snow1 and that           

manifestations of light are always      
accompanied by thunder--manifestations  
of light 7lampi71 thunder and rain being
 most closely connected4 ,we may have   
rain without manifestations of light1   
but never the latter without rain or    
hail4 ,i cannot here repeat what ,i have
 demonstrated in other memoirs2 ,i can  
only say that the lightnings of         
,vesuvius1 erroneously believed to be   
not accompanied by thunder1 are really  
not accompanied by rain1 but are induced
 by the descent of ashes and lapilli4#f 
,,general ,,conclusions4   ,we may      
conclude from what ,i have stated3  #a4 
,that by the assiduous study of the     
central crater1 and the indications     
afforded by the ,apparatus of           
,variations and the ,electro-,magnetic  
,seismograph1 we can obtain precursory  
signals of eruptions2 and that the other
 premonitory signs pointed out by our   
ancestors1 such as the drying up of     
wells1 either only happen occasionally  
or are mere coincidences1 such as those 

of the coincidence of a dry or a rainy  
season1 the prevalence of certain winds1
 etc4,f  #b4 ,that the fumaroles of the 
lavas are communications between the    
external surface of the lava1 hardened  
and more or less cooled1 and the        
interior lava still pasty1 or at least  
incandescent4  #c4 ,that from the lava1 
while flowing1 there is no escape of    
acid vapours1 neither from the fumaroles
 at the first period of their existence1
 but these1 if they last long enough1   
arrive at an acid period4  #d4 ,that    
hydrochloric is the first acid that     
appears1 combined afterwards with       
sulphurous acid1 and1 still later1 with 
sulphuretted hydrogen4  #e4 ,that       
vigorous lava streams may have eruptive 
fumaroles4 7,see ,translator's ,note #b 
to p4 #id47  #f4 ,that the sublimations 
follow a certain order in their         
appearance4 ,in the neutral period we   
get sea-salt mixed with some metallic   
oxides1 the first of which is oxide of  
copper4 ,but in the great lavas1        

chloride of iron appears simultaneously 
with the acid period4 ,hydrochloric acid
 transforms the oxides into chlorides1  
which1 in their turn1 change into       
sulphurets or sulphates on the          
appearance of sulphurous acid4  #g4     
,that the acids1 by attacking the scori1
 create new chlorides and sulphates1    
which are thus not products merely of   
sublimation4  #h4 ,that micaceous       
peroxide of iron--so common and abundant
 near the eruptive mouths--is very      
scarce and rare on the lavas1 unless    
conveyed there from the craters4  #i4   
,that chloride of iron--so manifest on  
the fumaroles of the great lavas--is    
only found in small eruptions close to  
the discharging mouths4  #aj4 ,that the 
frequency of chloride of iron in the    
lavas of great eruptions masks the order
 of transformation of the other         
products4  #aa4 ,the fumaroles at the   
summit of ,vesuvius present even greater
 gradations1 for they often emit        
carbonic acid or pure watery vapour4    

#ab4 ,lead1 which ,i first discovered in
 the fumaroles of the lavas of #ahee1 is
 a constant product of fumaroles which  
have a certain duration4 ,it is often   
obtained as a distinct and crystallized 
chloride1 and often is found in         
combination with other products4  #ac4  
,oxide of copper is also a constant and 
primary 7primitivo7 product of          
fumaroles4 ,the chloride and sulphate of
 copper are formed from the oxide1      
directly contrary to general belief4    
#ad4 ,i do not think that the chloride  
of calcium1 which ,i found on this      
occasion in almost all the deliquescent 
sublimations1 is a product peculiar to  
this eruption only1 in which alone1     
however1 ,i found it4 ,i was1 therefore1
 induced to look for it in other        
sublimates1 in which ,i might possibly  
have overlooked it1 as1 without doubt1  
my predecessors have done1 owing to the 
deliquescence of the chloride of iron   
with which it was constantly combined4  
,i think that this chloride1 in         

accordance with the general law1 is     
transformed into a sulphate--a          
transformation which readily occurs on  
,vesuvius4  #ae4 ,copious and           
well-crystallized sal ammoniac is only  
found on the fumaroles of those lavas   
which have covered cultivated or wooded 
ground4  #af4 ,the scarcity of oxygen in
 the gases of fumaroles may possibly    
arise from the formation of the oxides  
which precede the chlorides4  #ag4      
,lavas give a continuous spectrum1      
although covered with smoke1 when looked
 at with ,hoffmann's spectroscope with  
direct vision4,g  #ah4 ,the smoke gives 
positive electricity1 and the falling   
ashes negative electricity4             
,,reference ,,to ,,the ,,plates4        
,,plate  ,ia4 ,the ,cone of ,vesuvius1  
in #ahgj1 from a ,photograph taken      
near the ,observatory4      a4 ,the     
,atria del ,cavallo4   b b4 ,fossa della
 ,vetrana4     c4 ,punta del ,crocella4 
d4 ,lava of #aheh and #ahfg4     e4     
,police ,barrack near the ,observatory4 

f4 ,part of ,monte ,somma4  ,i,ia4      
,profile of ,vesuvius1 taken from a     
,photograph of the      ,observatory in 
the month of ,september1 #ahga4      #a4
 ,the ,cone1 on the #acth ,january1     
#ahga4  #b1 #b4 ,lava of #ahga4         
,i,i,ia4 ,profile of ,vesuvius on the   
#afth ,april1 #ahgb1 about ten          
days before the last ,conflagration4    
,i,va4 ,vesuvius1 on the #bfth ,april1  
#ahgb1 from a ,photograph taken      in 
the neighbourhood of ,naples4      #a4  
,the ,observatory4     #b4 ,fossa della 
,vetrana4     #c4 ,eruption of ,smoke   
and ,ashes1 with ,stones1 from the      
surface of the ,lava4     #d4 ,the      
,novelle1 ,st4 ,sebastiano1 and ,massa4 
#e4 ,lava which took the direction of   
,resina4     #f4 ,lava which1 from the  
,crater1 took the direction of the      
,camaldoli4     #g4 ,the ,grain ,stores1
 near ,naples4     #h4 ,resina4     #i4 
,torre del ,greco4    #aj4 ,the         
,camaldoli4  ,va4 ,profile of ,vesuvius 
after the ,eruption of the #bfth ,april1

     #ahgb1 from a ,photograph taken    
near the ,observatory4     #a1 #a4 ,the 
,fissures of the #bfth of ,april4    #b1
 #c4 ,small ,hill thrown up on the      
morning of the #bfth of          ,april1
 from below which issued the great      
current of          ,lava4 #d1 #d1 #d4  
,the ,mouths out of which the ,lava     
issued4    #e1 #e4 ,the larger ,lava    
,stream1 which passed near the          
,observatory          by the ,fossa     
della ,vetrana4    #f1 #f4 ,the other   
,lava ,stream1 which1 after dividing    
from          the last1 took the        
direction of ,resina4    #g1 #g4 ,the   
,lava which ran down towards the        
,camaldoli4   #h  #i4 ,the two ,craters 
on the summit of the ,cone4  ,v,ia4 ,the
 ,bifilar ,electrometer of ,signor      
,palmieri4      7,details47  ,v,i,ia4   
,the assemblage of the ,electroscopic   
,apparatus of ,signor       ,palmieri1  
as arranged at the ,vesuvian            
,observatory4  ,,viii4 ,professor       
,palmieri's ,seismographic ,apparatus4  

,a ,this small cone1 as it appeared on  
the #ast ,april1 is described and drawn 
in a ,memoir of ,professor von ,rath1 of
 the ,university of ,bonn1 on ,vesuvius 
on the #ast and #agth of ,april1 #ahga4 
,b ,eight young medical students        
perished beneath the lava1 with others  
unknown by name4 ,they were all youths  
of good promise2 their names will be    
recorded on the marble monument to be   
erected near the ,observatory4 ,they    
are3 ,girolamo ,pausini1 ,antonio and   
,maurizio ,fraggiacomo1 ,francesco      
,binetti da ,molfettu1 ,giuseppe        
,carbone da ,bari1 ,francesco           
,spezzaferri da ,trani1 and ,giovanni   
,busco da ,casamassima and ,vitangelo   
,poli4  ,c ,if this enormous height of  
projection really means1 that above the 
brim of the crater1 it involves an      
initial velocity of projection of above 
#fjj feet 7,british7 per second4        
,observations of the height of ascent of
 volcanic blocks are always difficult   
and deceptive1 and never free from      

error4--,translator4  ,d ,assuming these
 flashes to have emanated from somewhere
 within the cloudy volume of steam and  
dust called the head of the pine-tree1  
this interval would indicate that the   
mean height of this cloudy volume itself
 was not more than about four thousand  
feet above the top of the cone2 and1 if 
so1 that is not very far from the limit 
in height of projection of the dust and 
lapilli4--,translator4  ,e ,,cotunuite1 
chloride of lead1 in white1 lustrous1   
acicular crystals1 of the trimetric     
system1 easily scratched1 ,sp4 gr41     
#ebch4  ,,tenorite1 peroxide of copper1 
in thin1 hexagonal plates or scales1    
translucent when very thin1 dark steel  
gray1 of the cubic system2 hard and     
lustrous4 ,sp4 gr4 about                
#eiej4--,translator4  ,f ,earthquakes1  
though in distant regions1 usually      
precede eruptions4 ,the ,earthquake of  
,melfi preceded the great ,eruption of  
,etna in #aheb2 the ,earthquake of      
,basilicata of ,december1 #aheg1        

terminated with the ,eruption of #aheh1 
which filled the ,fossa ,grande with    
lava2 the ,earthquakes of ,calabria of  
#ahfg and #ahgj were the precursors of  
the ,vesuvian conflagrations of #ahfh1  
#ahga1 #ahgb4 ,a ,volcano1 also1 in the 
,island of ,java had a great eruption in
 the month of ,april1 some days before  
the last conflagration of ,vesuvius1 as 
,i learnt from a letter addressed to    
,signor ,herzel1 ,swiss ,consul at      
,palermo1 communicated to me#g by the   
astronomer1 ,signor                     
,cacciatore4--,palmieri4  ,g ,i have    
made a large collection of sublimates1  
which ,i purpose examining with the     
spectroscope1 and ,i shall be able to   
place some at the disposal of           
experimentalists who may desire to      
pursue investigations of this kind4     
,,notes  ,,by ,,the ,,translator4   #a  
7,p4 #hb1 text74 ,professor ,palmieri   
has not given any description in this   
,memoir of his seismograph--the         
instruments described being those only  

which have relation to atmospheric      
electricity4 ,the following brief       
account of his seismograph will1        
therefore1 form a not unsuitable        
complement to his ,memoir4 ,the         
instrument1 in general terms1 is of that
 class in which the wave movements are  
indicated by the displacement1 relative 
or absolute1 of columns of mercury in   
glass tubes4 ,it is a self-recording    
instrument1 composed of two distinct    
portions--one for record of horizontal1 
or rather of what are called undulatory 
shocks2 the other for vertical shocks4  
,in point of general principle1         
therefore1 it is very similar to that   
proposed by me 7,transactions1 ,royal   
,irish ,academy1 in #ahdf71 and in      
certain respects appears to me less     
advantageous than the latter4 ,some     
account of the ,palmieri instrument1    
together with some critical remarks as  
to its action1 may be found in my       
,fourth ,report on ,earthquakes         
7,reports1 ,british ,association1 #aheh1

 pp4 #ge-ha74 ,the following description
 of the instrument is derived from ,the 
,engineer1 of #gth ,june1 #ahgb1 and the
 publishers have to thank the           
proprietors of that journal for         
permission to use the illustration1     
,plate #h4  ,in ,fig4 #a1 ,e is a helix 
of brass wire 7gauge about one          
millimetre72 the helix consists of      
fourteen or fifteen turns1 and has a    
diameter of from twenty to twenty-five  
millimetres2 it hangs from a fine metal 
spring1 and can be raised or lowered by 
a thumb screw4 ,from the lower end of   
the helix hangs a copper cone with a    
platinum point2 the latter is kept close
 to the surface of mercury in the iron  
basin1 f1 which rests on an insulating  
column of wood or marble1 ,g4 ,the      
distance of the point from the surface  
of the mercury remains constant1 as the 
metal pillar1 ,t1 is of such a length   
that its expansion or contraction by    
change of temperature compensates that  
of the helix2 the latter is in          

connection 7by ,t7 with one pole of a   
,daniell's battery of two cells1 and the
 basin1 f1 is connected with the other  
pole4 ,any vertical movement1 however   
slight1 makes the platinum point dip    
into the mercury1 and thus completes the
 circuit4 ,in this circuit are included 
two electro-magnets1 ,c and ,d2 these1  
during the circulation of a current1    
attract their armatures1 which are      
connected with levers4 ,the action of   
,c's lever is to stop the clock1 ,a1    
which thus records1 to a half-second1   
the time of the occurrence of the shock1
 at the same instant that the clock     
strikes an alarm bell1 which attracts   
the attention of an observer4 ,the      
lever1 attached to the armature of ,d1  
at the first instant of the current     
frees the pendulum of the clock1 ,b1    
which was before kept from swinging1 in 
a position out of the vertical2 the     
clock then acts as a time-piece1 and its
 motion unrolls a band of paper1 k k k1 
at a rate of three metres an hour4 ,at  

the same time the armature of ,d1 while 
attracted1 presses a pencil point       
against the band of paper which passes  
over the roller1 m1 marking on it1 while
 the earthquake lasts1 a series of      
points or strokes which occupy a length 
of paper corresponding to its duration1 
and which record the work of the shock4 
,after it is over the paper continues to
 unroll from the drum1 i1 and passing   
round the clock1 rolls on to the drum1  
l4 ,if a fresh shock occur the pencil   
indicates it1 as before1 on the paper1  
and the length of blank paper between   
the two sets of marks is a measure of   
the interval of time between the shocks4
 ,by way of additional check1 several   
helices1 h h h1 are hung from a stand1  
with small permanent magnets suspended  
from their ends2 below and close to     
these latter are small basins1 holding  
iron filings2 into these the points of  
the magnets dip1 when their helices     
oscillate vertically1 and some filings  
remain sticking to the magnets as a     

record of the shock4 ,one of the magnets
 has a shoulder on it which moves an    
index hand along a graduated arc1 as    
shown in ,fig4 #b1 thus again           
registering the amount of the vertical  
movement4 ,such are the arrangements    
intended for the record of the          
undulatory or horizontal elements of the
 wave of shock4  ,the following are the 
arrangements proposed for recording the 
horizontal motions3 ,on the stand1 to   
the right of the clock1 ,a1 are set four
 ,u-shaped glass tubes1 open at their   
ends4 ,one of each pair of vertical     
branches must have a diameter at least  
double that of the other4 ,these pairs1 
with their supporting columns1 are shown
 in plan1 where one pair lies ,n4 and   
,s41 another ,e4 and ,w41 a third ,n4,e4
 and ,s4,w41 and the other ,n4,w4 and   
,s4,e4 ,it will be observed that        
metallic bars pass from the pillar1 ,p1 
over the ends of all the long branches1 
and similar bars pass from ,r1 over the 
ends of the short branches2 the pillars 

themselves1 as in the case of the other 
instruments1 are each connected with one
 pole of a ,daniell's battery1 the      
connections including the               
electro-magnets1 ,c and ,d4 ,the        
description of one ,u tube1 n1 will     
apply to all the others2 n is partly    
filled with mercury1 and an iron or     
platinum wire1 o1 suspended from the bar
 above the short branch1 dips into the  
mercury therein1 while another platinum 
wire hung from the bar over the mouth of
 the longer branch1 has its end very    
close to the surface of the mercury in  
that branch4 ,any shock which is not    
perpendicular in direction to the plane 
of the branches of the ,u will cause the
 mercury to oscillate in the tubes1 and 
more sensibly in that with the smaller  
diameter2 when it rises up in the       
latter1 so as to touch the platinum     
point1 the connection between ,p and ,r 
is made and the circuit completed1      
starting the action of the              
electro-magnets ,c and ,d1 which record 

the shock1 as already described4 ,by    
having the planes of the tubes set in   
the different azimuths1 already         
mentioned1 one or more of the pairs is  
sure to be acted upon1 and by observing 
in which the oscillation takes place the
 direction of the shock is supposed to  
be ascertained4 ,besides this1 each long
 branch of the ,u1 viz41 that of smaller
 diameter1 has a small ivory pulley1 q1 
fixed above it1 over which passes a     
single fibre of silk1 with an iron float
 at one end1 resting on the surface of  
the mercury2 at the other end of the    
fibre hangs a counterpoise2 fixed to the
 pulley is a fine index hand1 capable of
 moving along a graduated arc4 ,when the
 shock takes place the mercury1 rising  
in the long branch1 raises the float on 
its surface1 the silk fibre at the same 
time makes the pulley revolve with its  
index hand1 which afterwards remains    
stationary1 as the counterpoise prevents
 the float from sinking again with the  
mercury4 ,the reading on the graduated  

arc is thus a measure of the movements  
produced in the instrument by the       
horizontal element of the shock1 and is 
supposed to measure that shock4 ,it is  
assumed that in all these instruments   
shocks1 however small1 can be recorded  
with certainty by adjusting the distance
 between the platinum points and the    
mercury4  ,the arrangement of ,daniell's
 battery used for the seismograph is    
shown in ,fig4 #d1 where1 for           
convenience of cleaning1 the copper     
element is made of wire 7about ,no4 #h  
,birmingham wire gauge7 coiled flat     
without the spirals touching4 ,crystals 
of sulphate of copper are placed at the 
bottom of the outer cell1 into which    
water is poured2 and the inner cell1    
into which the zinc plate goes1 is      
filled with siliceous sand4  ,in        
addition to the above some instruments  
of a rougher description are employed as
 checks4 ,thus1 at the foot of the      
pillar1 ,g1 there is a wooden trough    
with eight holes1 facing as many        

equidistant points of the compass 7two  
of them shown in section7 round its     
inner circumference2 mercury is poured  
into the basin until its level is nearly
 up to the lips of the holes4 ,the      
effect of a shock is to throw some of   
the mercury into one or more of these   
holes1 and the greater the oscillation  
the more mercury is thrown into the     
cells through the holes4 ,the screws    
shown outside are for drawing off the   
mercury from the cells1 when its        
quantity can be measured4 ,the direction
 of the shock is shown by seeing which  
cells are filled with mercury4 ,this is 
the old ,cacciatore seismometer which   
has been long employed in ,italy4 7,see 
#d ,report of ,british ,association1    
#aheh1 p4 #gc71 and ,daubeny's          
,volcanoes1 ,appendix4 ,the following is
 another contrivance4 ,from the arm of  
the pillar1 ,g1 a fine metal wire hangs1
 with a metal ball at its end1 which1 by
 its oscillation1 thrusts out one or    
more light glass tubes1 set horizontally

 in a stand1 as shown in ,fig4 #c4 ,the 
two rings are of wood1 and the glass    
tubes pass through holes in them2 small 
leather washers are placed outside the  
outer rings2 the displacement of one or 
more tubes is assumed to measure the    
horizontal element of the shock4 ,by    
means of this apparatus the time of the 
first shock is recorded1 as well as the 
interval between the shocks1 and the    
duration of each2 their direction1      
whether vertical or horizontal1 is      
given1 as also the maximum of intensity4
 ,professor ,palmieri has the           
instruments examined three times a day1 
and an assistant-observer is always at  
hand to attend to the bell1 and put back
 the apparatus to its normal position   
for fresh observation4  ,it has been    
stated that this instrument is sensible 
to most of the shocks which occur in the
 ,mediterranean basin4  ,it is not my   
intention here to offer any criticism as
 to the construction or performances of 
this instrument1 the rather as ,i must  

confess ,i do not quite share the high  
opinion of its inventor as to the       
certainty or exactitude of its          
indications4  ,there can be no question 
as to the extreme importance to science 
of the establishment and continued use  
of a seismographic instrument of        
unexceptionable construction at the     
,observatory upon ,vesuvius2 and it     
would be a valuable gift to science1    
were the ,italian ,government to enable 
,signor ,palmieri to establish such an  
one4 ,its great value and the very first
 problem to set the instrument to solve 
should be1 by a rigid determination of  
the direction of propagation of the wave
 of shock1 of those slight or stronger  
pulsations which precede or accompany   
the ,vesuvian like all other eruptions1 
on arriving at the ,observatory1 to fix 
the depth1 and the position vertically  
beneath the cone1 whence these pulses   
are derived4 ,this would be1 in fact1 to
 fix the depth and position beneath the 
mountain at which the volcanic focus is 

situated for the time1 or1 at least1    
where the volcanic activity is at the   
time greatest4 ,and the assured         
knowledge1 even within moderate limits  
of accuracy1 of this depth1 and even for
 this single mountain1 would be an      
immense accession to our positive       
knowledge1 and a really new stage gained
 for future advances4 ,at present1 we   
know but little as to the actual depth  
below our globe's surface at which      
volcanic activity occurs1 or to which it
 is limited1 either upwards or          
downwards4 ,i have1 myself1 established 
some data upon the flanks of ,etna1 not 
yet published1 which may enable me to   
afford some information on the subject  
hereafter4 ,meanwhile1 ,professor       
,palmieri possesses unrivalled          
opportunities for such observations2 and
 ,i trust health1 life and means may be 
afforded him1 to become the first who   
shall have made this great addition to  
our positive knowledge of ,vulcanology4 
,so far1 popularly at least1 the alleged

 chief uses and value of these          
seismographic instruments1 at the       
,observatory of ,vesuvius1 have been    
made to depend upon their being presumed
 to afford means for foretelling        
eruptions1 or affording precursory      
warnings of their probable progress and 
destructive course4  ,i feel compelled  
to express my own total disbelief in the
 possibility of any such predictions in 
the present state of science1 by the    
help of any instruments whatsoever1 of  
such a nature as to be of any practical 
value1 or any certainty beyond that     
which a certain amount of mere          
experience as to the rle commonly played
 by ,vesuvius or other ,volcanoes in    
pretty habitual activity affords to the 
observer for a lengthened period4 ,and  
even this affords scarcely any guide as 
to what may happen next4 ,monte ,nuovo  
was thrown up in a night2 ,vesuvius     
might double its volume in a night1 or  
might sink into a hollow like that of   
the ,val del ,bove in a not much longer 

time4 ,a small fusillade may go on for  
months1 and yet1 without an hour's      
notice1 by any premonitory sign1 may    
waken up to a roar and darken the air   
with ashes and lapilli such as those    
which overwhelmed ,pompeii4 ,one        
eruption may blow forth little but dust 
and ashes 7so called71 another may pour 
out rivers of lava and little else4     
,the main mischief of all eruptions is  
effected in two ways3 by the deposit of 
dust and ashes1 lapilli1 etc41 to the   
injury or destruction of fertile land1  
and by the streams of lava which        
overwhelm it1 as well as buildings1 etc4
 ,but what information of any value can 
seismographic observation afford as to  
the course that either of these may take
 in any eruption8 ,the volume of        
pulverulent material that may be ejected
 cannot be foreseen2 its distribution   
depends mainly upon its nature and upon 
the direction and force of the wind at  
the time2 or again1 how shall these warn
 us as to the course that the lava1 if  

it appear1 shall take1 when we cannot   
possibly foretell when1 how1 or by what 
mouth it may issue4 ,even in this late  
eruption of #ahgb1 with ,palmieri       
stoutly at his post upon the mountain1  
and the ,observatory instruments in full
 activity1 they gave no forewarning of  
the sudden and unexpected belch forth   
from the base of the cone1 of that      
tremendous gush of liquid lava which in 
a few minutes cut off from life the     
unhappy visitors whose deaths he has    
recorded4  #b 7,p4 #id74 ,it can        
scarcely be supposed that these small   
eruptive-looking belchings forth from   
the lava stream1 en route1 are truly of 
an eruptive nature at all1 i4e41 in any 
way connected with forces seated deeply 
beneath the bed of the lava stream1 or  
in any way connected with the volcanic  
ducts of the cone or beneath it4 ,they  
are most probably merely the bursting   
upwards of large bubbles2 that is1 of   
cavities formed in the mass of the more 
or less liquid lava by intestine        

movements1 as its mass winds and rolls  
along1 and by the aggregation of smaller
 cavities--all being filled with steam  
and gases--together with dust and       
volatile products which are ejected when
 the cavity opens up1 and its contents  
escape at the upper surface of the lava 
stream in virtue of the continuation of 
the twistings and convolutions due to   
the stream motion itself1 and to the    
unbalanced hydrostatic pressures acting 
upon the parietes of the bubble4 ,very  
large single bubbles of like character  
rise in the fluid lava within craters in
 vigorous action1 and often so regularly
 that their recurrence causes a sort of 
rhythmical rush and roar in the column  
of steam1 etc41 issuing above the mouth4
 ,this was evident in the discharges    
issuing in #aheg from the highly        
instructive minor bocca1 then existing1 
examined by me1 and referred to         
7,report1 ,naples1 ,earthquakes1 etc4   
,vol4 ,,ii41 pp4 #cac1 #cad71 as        
presenting at the time great facilities 

for determining pyrometrically the      
temperature of the lava within1 and of  
the dry superheated steam issuing with a
 rhythmic roar from it4 ,m4 ,le ,coq    
7poques ,gologiques d',auvergne1 ,tome  
,,iv47 has recorded some examples of the
 formation and opening-out of large     
bubble-like cavities in lava already    
ejected4 ,perhaps that able and         
laborious vulcanologist1 whose death a  
few months ago science still deplores1  
attributes too much importance as well  
as magnitude to them1 when attributing  
the formation of what he has denominated
 craters of explosion1 to the mechanism 
of the rise and bursting of such bubbles
 upon a gigantic scale4 ,such blowings  
forth1 sudden or prolonged1 from        
particular spots of lava streams1 en    
route1 undoubtedly may also have their  
origin in damp places1 or water or      
air-filled cavities in or beneath the   
bed over which the lava rolls1 which1   
getting gradually heated1 generate      
steam1 or air or gases under tension by 

expansion1 etc41 which thus at length   
blow through the liquid or pasty lava   
flowing above1 and which in bursting    
through delivers much dust also1 and so 
simulates a little eruptive crater4     
,examples of this1 upon a great and     
convincing scale1 can be pointed to in  
the ,val di ,calanna and elsewhere on   
,etna4  #c 7,p4 #if74 ,there are strong 
grounds for the gravest doubts that     
there exists any real connection of a   
physical character between ,volcanic    
,eruptions1 and ,earthquakes more or    
less approximately coincident only1 in  
time of occurrence2 the respective sites
 being widely apart1 and the less the   
probability as the intervening distance 
is greater4 ,the discussions of the     
large number of records that are to be  
found of such coincidences--mostly but  
partial1 and in but very few instances  
complete coincidences--by ,perrey1 von  
,hoff1 and others1 as well as by myself1
 do not tend to sustain the view that   
such imperfect contemporaneity is based 

upon any causative connection4 ,the     
seismic region of ,greece appears to    
have no direct connection with that of  
,southern ,italy3 the band of           
connection1 if any1 seems to lie between
 ,northern ,italy1 across the ,northern 
,adriatic1 by ,ragusa1 and thence       
spreading into ,asia ,minor4  #d 7,p4   
#ig74 ,the abundance of coleoptera and  
of various other forms of insect life   
about lava beds1 both recent and old1 is
 a very singular fact1 and one worthy of
 the careful observation of             
entomologists4 ,in the autumn of #ahfd1 
at mid-day1 when sitting sketching upon 
the lava about the middle of the ,val   
del ,bove 7,etna71 ,i found it almost   
impossible to work1 or even to remain   
for an instant still1 in consequence of 
the continual cloud of insects1 large   
and small1 that struck against me in    
flight1 endangered the eyes1 and swarmed
 upon my clothes4 ,it is quite possible 
that this local superabundance of insect
 life may arise merely from the general 

dryness and warmth of such places1 and  
the plentiful nidus that the innumerable
 cavities in lava afford for the eggs   
and earlier stages of insect life2      
still1 this apparition of one form of   
life may also be connected with other   
circumstances not unimportant to        
discover4  #e 7,p4 #abj74 ,the ,crocella
 is a small wooden cross1 erected       
several years ago1 and which one passes 
to the right hand at the upper end of   
the path along the ridge of tufa and    
volcanic conglomerate upon which the    
,observatory stands1 in ascending thence
 to the ,atria del ,cavallo4  #f 7,p4   
#acd74 ,that the causes assigned by     
,professor ,palmieri for the potent     
developments of electricity 7positive or
 negative7 which characterise the ascent
 of the issuing columns of 7chiefly if  
not always7 dry steam1 with a relatively
 small volume of various gases1 and     
throwing up1 in their blast1 volumes of 
small solid particles in ashes and      
lapilli1 etc41 and the subsequent fall  

as a mineral or stony hail-shower of the
 latter1 through the partially          
condensing vapours and the circumambient
 air1 are the main causes of electrical 
development evidencing itself in        
lightning flashes1 is no doubt true4 ,we
 must not1 however1 lose sight of the   
many other and very effective agencies  
at work here to produce electric        
excitement4 ,the actual bocca of the    
volcanic vent whence the steam roars off
 constitute the cone a veritable        
hydro-electric machine4 ,mechanical     
energy in various forms is transformed  
into electric energy4 ,chemical action  
is going on both in the solid and in the
 vapourous and gaseous emanations as    
they rush into and remain in the air or 
descend from it1 and chemical action is 
transformed in part into electric       
energy4 ,percussion between ascending   
and descending particles and fragments1 
fractures and breaking up of more or    
less of these1 thus and by sudden       
changes of temperature in cooling1 are  

likewise operative4 ,in addition1 great 
and violent movements in the atmosphere 
itself result from the large local      
accessions of temperature by the heated 
volume driven up into it1 and which in  
turn give rise to electric disturbance  
of the same character as those produced 
in wind storms and whirlwinds1 brought  
about by the natural causes which every 
day effect disturbances in our          
atmosphere all over the globe4  #g 7,p4 
#ace74 ,the views stated in note #c 7to 
page #if7 may here again be referred to 
as in point4 ,how is it possible1 in the
 present state of science at least1 to  
establish any physical connection       
between an eruption in ,java and one of 
,vesuvius1 with half the world between1 
when not even having the solitary       
connecting link of complete             
contemporaneity1 and which1 if it       
existed1 yet might be nothing but       
accidental8 ,a list of shocks upon      
record1 which have occurred more or less
 nearly simultaneously at distant parts 

of the world1 may be found in my fourth 
,report1 7,facts of ,earthquakes1       
,british ,association ,reports1 #aheh7  
and the reasons are there given for     
rejecting the notion of any direct      
physical connection between the origins 
of the respective shocks4  ,shocks1     
emanating from the close neighbourhood  
of volcanic vents1 or simultaneity of   
eruption1 in vents not far distant from 
each other1 stand upon a different      
footing4     ,transcriber's ,notes4     
,preserved the unusual1 but consistent1 
spelling of develope4  ,preserved the   
unusual1 and inconsistent1 references to
 the ,plates4 ,sometimes ,arabic        
numerals are used1 but usually ,roman   
numerals4 ,most have ,a attached to the 
name 7which was changed to a to avoid   
confusion in the ,roman numerals71 but  
not ,,viii1 and sometimes not in the    
references to them4  ,equations were    
converted to linear text1 adding spacing
 and parentheses as necessary4 ,greek   
characters were also replaced by ,latin 

letters in the ,latin-#a version4       
,replaced the oe ligature with the two  
characters in ,goethe in the front      
material4  ,changed fumarolles to       
fumaroles on page #c3 fumaroles and     
salfatares4  ,changed ,lyall to ,lyell  
in footnote originally on page #i3      
,daubeny1 ,lyell1 ,phillips and others4 
,changed throught to through on page    
#ce3 passing through it4  ,removed      
duplicated word the on page #dj3 the    
great ,calabrian ,earthquake4  ,page #hi
 refers to the ,fossa del ,vetrano2     
elsewhere there are references to ,fossa
 della ,vetrana1 which may be what was  
intended4 ,however1 ,i did not change   
this4  ,changed hydrochloride to        
hydrochloric on page #aji3 the          
hydrochloric acid which it discharged4  
,changed disk to disc on page #abf3 the 
disc and index4  ,replaced the infinity 
symbol on page #aca with for infinity1  
in the ,latin-#a text version4  ,changed
 azismuths to azimuths on page #adc3 the
 different azimuths4  ,changed silicious

 to siliceous on page #adc3 filled with 
siliceous sand4