,transcriber's ,notes ,superscripts are indicated by caret symbols3 #bh for single characters and #ba4e for multiple characters4 ,italic text is enclosed in underscores4 ,other notes will be found at the end of this e,book4 ,the ,destinies of the ,stars ,by ,svante ,arrhenius1 ,ph4,d4 ,president1 ,nobel ,institute1 ,stockholm1 ,sweden 7,recipient of the ,nobel ,prize in ,chemistry1 #aijc7 ,authorized ,translation from the ,swedish ,by ,j4 ,e4 ,fries ,fellow ,a4,i4,e4,e4 ,illustrated ,g4 ,p4 ,putnam's ,sons ,new ,york and ,london ,the ,knickerbocker ,press #aiah ,,copyright1 #aiah ,,by ,g4 ,p4 ,,putnam',s ,,sons ,the ,knickerbocker ,press1 ,new ,york ,,translator',s ,,preface ,when ,dr4 ,svante ,arrhenius in the year #aijc received the ,,nobel ,,prize in ,chemistry it came as a fitting reward of his achievements principally in the electro-chemical field4 ,it was natural1 however1 that a genius of his calibre would not limit his interest to the 8infinitely small0 but would gradually broaden it to encompass the 8infinitely large40 ,and 8to take an interest0 means with ,dr4 ,arrhenius to push the boundaries of the unknown and of the unexplored a little farther away from man4 ,his evolution in this respect runs parallel with that of all the great men who stand out as leaders in the history of science4 ,wrapt up in the solution of a particular problem and fired with the divine yearning to reach ultimate causes they are inevitably driven to ever widening circles of research until this whole material universe1 its whence and whither1 becomes the overpowering passion of their spirits4 ,thus the mere titles of the works of ,dr4 ,arrhenius1 read in the sequence of their publication1 give us1 better than any biography1 the history of a soul1 which1 no matter what his unprofessed philosophical faith may be1 constitutes our strongest evidence in favour of that theory of 8purposiveness0 in the universe which ,dr4 ,arrhenius so heartily abhors 7and justly so7 when resorted to in natural science1 but which theory nevertheless 7and justly so7 is so dear to the philosopher3--,researches in ,regard to the ,conductivity of ,electrolytes2 ,conductivity of ,extremely ,diluted ,solutions2 ,chemical ,theory of ,electrolytes2 ,textbook in ,theoretical ,electro-,chemistry2 ,textbook in ,cosmological ,physics2 ,worlds in the ,making2 ,infinity of the ,universe2 ,life of the ,universe as ,conceived by ,man from ,earliest ,ages to the ,present ,time2--thus run the titles of a few of the works we already have by ,dr4 ,arrhenius' hand4 ,how were it possible for him ,,not to write ,the ,destinies of the ,stars8 ,the volume came as inevitably as fruition follows flowering4 ,what remains to be seen is if ,dr4 ,arrhenius can withstand the tremendous temptation that must be at work in his soul to lift1 be it ever so little1 the curtain that separates natural science and philosophy2 we hope he will give in2 we admire in this book how he reads 8,the ,riddle of the ,milky ,way02 we certainly wish to know how he reads--the riddle of the universe4 ,the ,destinies of the ,stars met with unexampled success in ,sweden4 ,three editions appeared within two months when the book was published in ,november1 #aiae4 ,the ,american version has been somewhat delayed principally due to war conditions4 ,this1 however1 has not been wholly a loss to the ,english-speaking world as ,dr4 ,arrhenius by no means has been idle in the meantime4 ,considerable additional subject matter1 including three new pictures1 has been added1 chiefly based on the most recent astronomical discoveries some of which have been recorded as late as #aiag4 ,for valuable suggestions and for all the ,american equivalents of the metric measures in the original1 the reader as well as the translator1 is indebted to a member of the ,publishing ,house that presents this volume in such an attractive way1 ,mr4 ,e4 ,w4 ,putnam1 himself an ardent lover of astronomy and a writer on the subject4 ,dr4 ,arrhenius is justly renowned for his lucid style and polished form4 ,all that is lacking in these qualities within the covers of this volume is wholly due to the deficiencies of the translator1 who however could not resist the temptation of transferring to ,anglo-,saxon soil this monument to the genius of his former teacher1 ,dr4 ,svante ,arrhenius4 ,j4 ,e4 ,,fries4 ,,birmingham1 ,,ala41 ,december #ae1 #aiag4 ,,preface ,since ,i presented ,worlds in the ,making and ,life of the ,universe as ,conceived by ,man from ,earliest ,ages to the ,present ,time to the public--which received them with far greater interest and appreciation than ,i could foresee--,i have had repeated occasions to treat new questions of a cosmological nature1 questions largely arisen from new discoveries and observations within the scope of astronomy4 ,vast new vistas have been opened through the study of the relation of the stars to the 8,milky ,way0 and through observations of our neighbour planets4 ,the last mentioned give plain indications of the course of planetary evolution and thus enable us to surmise the changing fate and future position of the ,earth4 ,in an earlier ,german publication1 ,das ,schicksal der ,planeten 7#aiaa71 ,i dealt with some of these problems4 ,as1 further1 the evolution of the solar system from the ,milky ,way nebula1 to which ,i have devoted several lectures at home and abroad1 may be considered as the pre-history of the evolution of the planets1 ,i have given this collection of cosmogenic articles the common title ,the ,destinies of the ,stars4 ,i offer as introduction a lecture delivered before the ,fourth ,international ,philosophical ,congress in ,bologna1 #aiaa1 dealing with the 8,origin of ,star-,worship40 ,hoping that this little book will1 to a considerable extent1 fill the gaps in my previous works1 ,i present these treatises in remodelled form4 ,,svante ,,arrhenius4 ,,stockholm1 ,november1 #aiae4 ,,contents ,,chapter ,i ,,page ,,origin ,,of ,,star-,,worship #a ,position and practical value of astronomy4 ,worship of stars4 ,chronology4 ,the ,australian negro's conception of the stars4 ,day and night1 summer and winter4 ,solar year4 ,sun-worship4 ,changing phases of the moon in chronology4 ,the ,mexican 8,tonalamatl40 ,moon-worship in ,mesopotamia4 ,significance of the moon in astrology4 ,the sun and the heat4 ,agriculture's demand on chronology4 ,worship of the planet ,venus by the ,mexicans and the ,babylonians4 ,the ,church ,calendar4 ,the ,zodiac4 ,the seven planets4 ,the week4 ,correspondence and sympathetic magic4 ,the ,platonic-,aristotelian philosophy4 ,astrology and alchemy4 ,tycho ,brahe4 ,occult sciences4 ,aristarchos from ,samos4 ,kopernicus4 ,the progress of ,astronomy4 ,,chapter ,,ii ,,the ,,mystery ,,of ,,the ,,milky ,,way #da ,primitive conceptions of the ,milky ,way4 ,anaxagoras and ,demokritos4 ,ptolemaios4 ,galilei4 ,cosmogenic speculations4 ,wm4 ,herschel's statistical researches regarding the distribution of the stars4 ,the ,milky ,way as the foundation of the stellar system4 ,the ,milky ,way as a nebula4 ,classification according to age of the stars1 their distribution and velocity4 ,motion in the ,orion nebula4 ,the planetary nebul4 ,kapteyn's 8star-drifts40 ,the origin of the ,milky ,way4 ,comparison between the ,milky ,way and a spiral nebula in 8,the ,dogs of ,orion40 ,a few details from the ,milky ,way4 ,the infinitely great and the infinitely small4 ,the magnitude and destiny of the ,milky ,way4 ,,chapter ,,iii ,,the ,,climatic ,,importance ,,of ,,water ,,vapour #hd ,the four elements of ,aristotle4 ,humid-warm climates4 ,the ,congo and ,amazon basins4 ,the carboniferous age4 ,the effect of cloudiness4 ,desert climate4 ,steppes4 8,kevirs0 and 8,bayirs40 ,sand dunes4 ,the great ,kevir4 ,climatic changes4 ,khanikoff's description4 ,salt lakes4 ,deposits of salt through evaporation4 ,huntington about the arefaction of the earth4 ,humid period during the ice-age4 ,climatic changes during historic time4 ,africa1 ,asia1 ,greece1 ,italy1 ,sicily4 ,west-,europe's climate has grown more marine4 ,present conditions4 ,,chapter ,,iv ,,atmosphere ,,and ,,physics ,,of ,,the ,,stellar ,,bodies #aai ,outer envelope of the stars4 ,the large planets4 ,spectra4 ,mars1 ,earth1 ,venus1 ,mercury4 ,atmosphere impossible on the moon4 ,the light from the ,earth4 ,the atmosphere of ,mercury4 ,the atmosphere of ,venus and its ,clouds4 ,composition of air and its change with height4 ,forced circulation4 ,troposphere and ,stratosphere4 ,hydrogen in the highest strata of the atmosphere4 ,water vapour and carbonic acid in the air4 8,geokoronium40 ,influence of gravity on composition of the atmosphere4 ,the air on ,venus and ,mars4 ,,chapter ,v ,,the ,,chemistry ,,of ,,the ,,atmosphere #aee ,inhabited ,worlds4 ,kinship of the stellar bodies4 ,presence of life4 ,importance of water and carbon4 ,importance of temperature4 ,all life evolved from existence in water4 ,necessity of oxygen4 ,bacteria4 ,reducing substances preponderable in the ,world-matter4 ,volcanic gases and gases in solidified lava4 ,water1 vapour1 carbon dioxide1 nitrogen gas1 and sulphurous acid4 ,permanent gases and hydrogen4 ,the poisonous character of the original air4 ,its purification4 ,the importance of plant life and necessity of a solid crust in this process4 ,supply of carbonic dioxide and production of oxygen4 ,the work of ,koene4 ,silica4 ,cooling of the ,earth and changing surface temperature4 ,the ice-periods4 ,centres of collapse and lines of fissure in the crust4 ,general survey of the gradual change of the air4 ,,chapter ,,vi ,,the ,,planet ,,mars #ahj ,the controversy about the habitableness of ,mars4 ,humidity on ,mars4 ,early observations4 ,the spectra of ,mars and of the ,moon compared4 ,investigations by ,campbell and ,marchand4 ,the work of ,lowell4 ,measurements by ,slipher4 ,calculations by ,very4 ,the temperature on ,mars according to these sources4 ,campbell's expedition to ,mount ,whitney in ,california4 ,oxygen on ,mars4 ,the cold on ,mars detrimental to anything but the lowest forms of life4 ,cause of different results by ,slipher and ,campbell4 ,very's answer to ,campbell's criticism4 ,new measurements by ,slipher4 ,campbell's new method of measurement of #aiaj4 ,christiansen calculates the temperature on ,mars from intensity of the ,sun's radiation4 ,the sun-constant4 ,average temperature of ,mars about forty degrees ,centigrade4 ,possibly low plant life around the poles during summer4 ,the canals on ,mars are probably fissures in the crust4 ,the length of the canals compared with that of the fissures in ,earth's crust4 ,the double canals on ,mars compared with the parallel fissures in ,calabria4 ,emanations along the fissures4 ,the canals as affected by increasing cold or heat4 ,the polar snow4 ,thawing of the canals4 ,travel of the water vapour independent of the topography4 ,the desert sand on ,mars4 ,clouds and mists4 ,highlands and mountains on ,mars4 ,sand filling of the canals4 ,the seas on ,mars4 ,the straightness and uniform breadth of the canals an illusion4 ,light and dark spots4 8,new0 canals4 ,the fancies of ,lowell4 ,,chapter ,,vii ,,mercury1 ,,the ,,moon1 ,,and ,,venus #bbh ,fissures on ,mercury4 ,lowell's drawing4 ,centres of collapse4 ,absence of atmosphere4 ,the climate on the ,moon4 ,w4 ,pickering's belief in frost formations on the ,moon4 ,the mountains on the ,moon4 ,volcanoes4 ,circular elevated rings4 8,seas0 on the ,moon4 ,the ,crater 8,linn40 8,sinuses0 and 8,streaks0 on the ,moon4 ,the light matter of the streaks probably lava-scum4 ,the colour of the ,moon and of the ,earth4 ,comparison between the ,moon and ,mars4 ,changes on the ,moon4 8,snow0 and 8,vegetation0 on the ,moon according to ,w4 ,pickering4 ,the fate of ,mars and of the ,earth4 ,falling meteoric dust4 ,the climate on ,venus4 ,swamps like those of the carboniferous age4 ,abundant vegetation4 ,low organisms4 8,culture0 on ,venus will proceed from the poles4 ,the future of ,venus4 ,the claims of astrology in modern light4 ,tycho ,brahe4 ,the dreams of ,giordano ,bruno probably true4 ,,illustrations ,,page ,,fig4 #a4--,,the ,,milky ,,way #df ,photo by ,easton4 ,,fig4 #b4--,,planetary ,,nebula ,,no4 #gjji1 ,,new ,,general ,,catalogue #eb ,,fig4 #c4--,,nebula ,,no4 #deid1 ,,new ,,general ,,catalogue #ff ,,fig4 #d4--,,nebula ,,no4 #aja ,,in ,,messier',s ,,catalogue #gj ,,fig4 #e4--,,nebula ,,no4 #ea ,,in ,,messier',s ,,catalogue #ga ,,fig4 #f4--,,milky ,,way ,,between ,,cassiopeia ,,and ,,swan #gf ,according to ,wolf4 ,,fig4 #g4--,,milky ,,way ,,in ,,eagle ,,and ,,sagittarius #gf ,according to ,wolf4 ,,fig4 #h4--,,the 8,,trifid0 ,,hole ,,in ,,eagle #gg ,according to ,wolf4 ,,fig4 #i4--,,tarim ,,river ,,with ,,lakes ,,and ,,bayirs #if ,according to ,sven ,hedin4 ,,fig4 #aj4--,,the ,,former ,,lake ,,bonneville ,,in ,,utah #ajf ,,fig4 #aa4--;,,jupiter1 #aiji #abb ,according to ,f4 le ,coultre4 ,,fig4 #ab4--,,saturn1 #aiji #abc ,according to ,f4 le ,coultre4 ,,fig4 #ac4--,,spectra ,,of ,,the ,,major ,,planets #abd ,according to ,v4 ,m4 ,slipher4 ,,fig4 #ad4--,,venus ,,observed ,,by ,,langley ,,in #ahhb #acf ,,fig4 #ae4--,,rock ,,fissure ,,at ,,hango1 ,,sweden #bjd ,photo by ,i4 ,i4 ,sederholm4 ,,fig4 #af4--;,,earthquake ,,centers ,,in ,,calabria #bje ,according to ,i4 ,i4 ,sederholm4 ,,fig4 #ag4--,,maps ,,of ,,mars ,,by ,,schiaparelli ,,and ,,antoniadi ,at the end ,,fig4 #ag;a4--,,maps ,,of ,,mars ,,by ,,schiaparelli ,,and ,,antoniadi ,at the end ,,fig4 #ah4--,,photo ,,of ,,mars ,,by ,,lampland #baj ,,fig4 #ai4--,,mars ,,on ,,april #h1 #aiji #baj ,according to ,quenisset4 ,,fig4 #bj4--,,the ,,south ,,pole ,,spot ,,on ,,mars1 #aiji #baj ,according to ,jarry ,desloges4 ,,fig4 #ba4--,,sandstorm ,,on ,,mars1 #aiji #baj ,according to ,antoniadi4 ,,fig4 #bb4--;,,cloud ,,on ,,edge ,,of ,,mars1 ,,the #g,,th ,,of ,,march1 #aija #baf ,according to ,molesworth4 ,,fig4 #bc4--,,mars1 ,,july #aa1 #aijg #baf ,according to ,lowell4 ,,fig4 #bd4--,,mars1 ,,october #f1 #aiji #baf ,according to ,antoniadi4 ,,fig4 #be4--,,mercury #bcj ,according to ,lowell4 ,,fig4 #bf4--,,the ,,moon ,,near ,,the ,,crater ,,tycho #bcj ,photo from ,yerkes ,observatory4 ,,fig4 #bg4--,,mare ,,serenitatis ,,and ,,mare ,,tranquillitatis #bca ,photo from ,yerkes ,observatory4 ,,fig4 #bh4--,,the ,,moon ,,near ,,its ,,south ,,pole #bdj ,photo from ,yerkes ,observatory4 ,,fig4 #bi4--,,the ,,lunar ,,crater ,,copernicus ,,and ,,vicinity #bdb ,photo from ,yerkes ,observatory4 ,the ,destinies of the ,stars ,,chapter ,i ,,the ,,origin ,,of ,,star-,,worship ,astronomy occupies a rather unique position among the natural sciences4 ,while physics1 chemistry1 and the biological sciences form the foundation of the extraordinary material development of our day1 astronomy1 in the eyes of most people1 is of little practical value4 ,what benefit could we derive from knowing whether a star lies a hundred or a thousand billion miles from the ,sun1 or from understanding how the stellar bodies have evolved in the course of billions of years8 ,and yet astronomy has not been as futile as is commonly imagined1 neither is it useless at the present time4 ,this science is still of the greatest importance to common life by fixing our standards of time and1 before the introduction of the compass1 was invaluable also to navigation1 which art1 moreover1 depends now upon astronomy for determination of geographical position on the open sea4 ,observations for these purposes1 however1 are of such a simple nature1 that they hardly fall under the astronomical science proper1 but rather under the applied sciences4 ,they have entered into daily life much as1 in commerce1 the determination of the weight of a body is not considered as belonging to the science of physics1 although it depends on the use of a physical instrument1 the scale4 ,but we must not forget that what we now consider so commonplace that it entirely has lost the grand aspect of science1 once was the goal of groping scientific endeavour4 ,all natural science has grown out of the needs of practical life4 ,geometry is probably even older than astronomy4 ,the name means3 to measure land1 and the oldest geometry was1 accordingly1 devoted to the measurement of distances on the ,earth and later to the determination of the area of land-holdings4 ,this extremely important practical application of geometry is of such a simple nature that it is not mentioned in modern mathematical science1 to which geometry belongs4 ,in this manner1 the original theses of all our natural sciences have become the possession of the public to such a degree that they are looked upon as self-evident4 ,this is the case also with those parts of astronomy which1 because of their practical importance at the outset1 gave rise to the science itself4 ,the growing knowledge about the stars1 like all higher insight1 became among primitive peoples the private possession of their leaders1 was by these kept a secret and made a part of the venerable realm of religion4 ,we find that a majority of these old peoples rendered worship to the stars1 believing them to govern the fates of human beings4 ,this may indeed seem highly remarkable1 as our everyday experience is that the stellar bodies1 with the exception of the ,sun1 exert no perceptible influence on organic nature1 and such conclusion is emphatically confirmed by the systematic collection of all our experiences which we call modern science4 ,the ,sun1 as stated1 is the exception as it reigns over the entire nature1 the living as well as the lifeless1 by virtue of the heat and light which abundantly flow from this autocrat of our planetary system4 ,perhaps the ,moon also plays some small active part as it seems somewhat to affect the barometric pressure1 the magnetic and particularly the electric conditions of the atmosphere1 which1 in turn1 appear to influence several life processes4 ,on the other hand we cannot point to any influence upon nature traceable to the other stellar bodies4 ,obviously1 primitive man devoted his thoughts only to such conditions as affected his interests in a beneficial or detrimental way4 ,on the assumption that these conditions were governed by spirits who resembled man and who in particular were endowed with will1 our ancestors endeavoured by sacrifice and exorcism to move the spirits they feared to discontinue their harmful activity4 ,some such spirits dwelt in beasts of prey and in other noxious animals1 such as poisonous snakes2 others caused earthquakes1 volcanic eruptions1 snowstorms1 lightning ravages1 fires1 floods1 heat1 drought1 etc4 ,against these calamities religious exercises formed a protection4 ,religion sprang mainly from fear of spirits4 ,later on thank offerings and hymns were bestowed upon benevolent objects and phenomena in nature4 ,it is evident that this primitive1 simple religion is of far greater age than star-worship4 ,the latter presupposes a comparatively high degree of culture4 ,the stars were of no benefit to man until it became necessary to measure time intervals comprising a greater number of days than might be counted on one's fingers4 ,how this growth in all probability took place we shall endeavour to explain in the following4 ,fairly certain it is that star-worship did not grow out of man's admiration for the sublime drama which at dawn of morning commences at the eastern horizon1 and proceeds in the course of a day over the firmament in order to close before night just beyond the western expanses1 neither was it founded on man's gratitude toward the torch-bearers of night for their incessant battle against gloomy clouds and all the other spirits of darkness4 ,even tribes on a rather low stage have no doubt noticed the most conspicuous among the stellar bodies4 ,the attitude of the ,australian aborigines is significant in this connection4 ,according to ,spencer and ,gillen they possess legends about the ,moon1 which is male1 about the ,sun and ,venus1 about the pernicious ,magellanic clouds1 and about the ,pleiades1 who1 like the ,sun and ,venus1 are considered female4 ,eclipses have1 as is natural1 attracted the greatest attention4 ,while these primitive men indulge in an incredible number of religious ceremonies pertaining to conditions of their daily life1 none of these exercises are devoted to the stars1 if we except stone throwing against the ,sun during eclipses4 ,even this treatment is left with considerable serenity of mind for the medicine-men to perform4 ,it is very significant that all stellar bodies are of earthly origin1 that the ,moon is of male gender while the ,sun1 ,venus1 and the ,pleiades are female1 which indicates that the ,moon is considered of greatest distinction4 ,they count time according to 8sleeps10 i4 e4 the number of times they have slept1 or according to moons2 longer periods according to seasons2 they have names for summer and winter4 ,they can count to five1 or perhaps rather to four1 as the term five also means 8many40 ,ideas of power centred in the stellar bodies are evidently absent and therefore also religious ceremonies pertaining thereto4 ,a few tales exist relating to the stars as to other objects within their observation4 ,thus conditions would undoubtedly have remained but for the high value which the want of a chronometry gave to the regularly changing light of the stellar bodies4 ,the difference between day and night is of such a deeply fundamental importance that it has left its stamp on the whole organic nature on the surface of the ,earth4 ,plants entirely change their life processes in the course of twenty-four hours2 during the day they add to their growth under the stimulus of light2 during the night they partly expend the strength gathered in daytime4 ,this cycle is so regular that it functions automatically4 ,the prominent botanist1 ,pfeffer1 has experimented with a ,mimosa1 which1 as is well known1 unfolds its leaves during the day but curls them during the night4 ,if left in a dark room any arbitrary day1 it nevertheless uncurls its leaves4 ,by means of electric light ,pfeffer changed night into day for the plant kept in the dark room4 ,it took considerable time before the plant adjusted itself to the new conditions so that it unfolded its leaves to the influence of the electric light4 ,animals behave similarly4 ,the night and day period is instilled in their blood4 ,in a certain sense they possess an instinctive chronometry4 ,it is often stated that the assurance of the return of sunlight after the darkness of night enabled humanity with greater equanimity to acquiesce in the loss of light during one half of its existence and that worship was rendered to the ,sun in gratitude therefor4 8,a new outlook upon life10 says ,troels ,lund1 8awakens the moment the great discovery is made that the night of sleep and the night of fear are equally long and always followed by morning and subsequent day40 ,this discovery1 however1 our predecessors made long before they reached the human stage4 ,sun-worship by no means derived its origin therefrom4 ,rather it is traceable to evidence of the ,sun's connection with the changing seasons1 although this change also is of domineering influence in the vegetable world inasmuch as the plants store reserve nourishment in the autumn1 particularly1 and on a large scale1 during fructification4 ,also1 lower and higher animals1 for example1 bees and squirrels1 gather winter-stores4 ,it is therefore small wonder if men on a comparatively low stage lay in provisions for the recurring periods of scant food supply4 ,but a true chronometry beyond five days is foreign to the ,australian negro as long as he can only count to four or five4 ,he is aware that ,moon-phases reappear and that summer and winter return1 but he has no conception of the duration of the time passed between the recurrences of these phenomena4 ,further progress was made by the people who took the bold step to count the fingers1 not on one hand alone1 but on both hands1 and thus reached the number ten4 ,this was utilized in reckoning time so that the larger unit became a decade1 i4 e4 ten days and nights4 ,this unit was original with the ,indo-,europeans1 ,semites1 ,hindus1 ,egyptians1 and the islanders in the ,pacific ,ocean4 ,another advance yet was made in ,mexico where the number twenty was introduced corresponding to the sum of all fingers and toes1 and thus a unit of time was obtained comprising twenty days and nights4 ,but to rise from these units to one of #cfe days was a step exceedingly difficult for the primitive peoples to take4 ,thousands of years elapsed before the most intelligent among the races established the length of the solar year4 ,those who lived in regions where the ,sun's altitude notably changes1 i4 e4 far from the equator1 undoubtedly reckoned time in years1 without knowing its length expressed in days4 ,imagine a nomadic tribe like the ,lapps in the north of ,sweden4 ,in the autumn their reindeer wander down toward the coast in search of food and the ,lapps go with them4 ,in spring the reindeer lead their masters back again to the mountains4 ,it cannot very well escape the observation of these nomads that the ,sun shines almost continuously during their stay in the uplands while dreary night reigns nearly without interruption during their sojourn in the lowlands4 ,they are obviously forced to co-ordinate the beautiful summer with the duration of sunlight4 ,to them1 therefore1 the ,sun's extraordinary great importance to life is unquestionable4 ,the same holds true about all people who live sufficiently far from the equator4 ,as a consequence1 they become ,sun-worshippers4 ,it is not difficult to find examples of peoples who have worshipped the ,sun2 only a few of the more important ones will be mentioned here4 ,the people of the bronze age here in the ,north were zealous ,sun-worshippers thousands of years ago1 as the many relics from this period1 and particularly the rock-carvings1 bear witness4 ,the ,celts of ,western ,europe have frequently symbolized the ,sun as a cross1 while the worship of ,moon and stars seems to have been foreign to them as well as to the bronze-age people of the ,north4 ,the ,jewish ,samson 7,simson7 was a ,sun-hero1 the name being related to the ,babylonian ,shamash1 the ,sun-god4 ,in ,hesiodos' cosmogony the ,sun 7,helios7 is mentioned before the ,moon 7,selene74 ,the old ,germans worshipped both ,sun and ,moon1 particularly the former4 ,the ,slavs possessed a ,sun-god ,dazbogu1 but no deity identified with the ,moon4 ,similar conditions obtained among the ,finnish forefathers4 ,the ,chinese ,tao-priests light fires during the vernal equinox as we do at ,walpurgis and midsummer1 and they sacrifice rice and salt to the flames4 8,this is a remnant of the ,sun-cult10 says ,solomon ,reinach1 from whom these data in regard to ,sun-worship principally are taken4 ,in ,japan1 the ,moon is of male sex1 the ,sun of female sex1 which indicates that there1 as with the ,australian negroes1 the ,moon was originally considered more important than the ,sun4 ,nevertheless the ,japanese are now ,sun-worshippers2 the ,sun is placed as emblem of the most high in their flag and the ,mikado is known to trace his lineage from the ,sun4 ,they have1 therefore1 long ago passed from ,moon-cult to ,sun-cult4 ,it is probable that this step was taken even earlier in ,china1 where the ,sun furthermore is of male sex4 ,with growing civilization all people learn to understand1 as have the ,japanese1 the superior importance of the ,sun4 ,the ,incas of ,peru1 who reached a very high grade of culture1 were sun-worshippers and called themselves children of the ,sun1 although they lived near the equator where the ,moon-cult1 as we presently shall see1 owns its most faithful adherents4 ,in the neighbourhood of the equator1 winter and summer differ very slightly with respect to temperature and altitude of the ,sun4 ,rather1 it is the alternation of humid and dry seasons that is of deciding importance4 ,no sheet of snow covers the ground in winter-time1 kills the vegetation1 or decimates the supply of nourishment for animals and men4 ,indeed1 contrary to our experience1 a suppression of growth often accompanies a high altitude of the ,sun due to the drought which simultaneously occurs4 ,the altitude and luminosity of the ,sun change altogether too slightly in the course of the year to attract the attention of primitive man4 ,the light of the ,moon1 on the other hand1 varies from full intensity to nothing and this takes place in periods so short that memory has no time to forget the cycle4 ,even the low-standing ,australian negroes utilize the phases of the ,moon to denote remote times4 ,chronometry in any true sense they do not possess1 unable as they are to state the number of days in a month4 ,how much more fortunate the peoples who could count to ten or better yet to twenty and thus were able to use the single or the double decade as a measure of time4 ,for them it was easy to determine the time between two successive phases of the ,moon1 seven and a half days apart4 ,the truth once grasped that four phases separate two new ,moons the important bridge could be established between the short measure1 a day1 and the longer measure1 a month4 ,the latter was then found to be nearly thirty times longer than the former4 ,on a higher stage of culture1 it was discovered that this ratio was not exact and the discrepancy must greatly have puzzled the people4 ,the correct ratio is #bi4ec4 ,at all events the periodic return of full ,moon and new ,moon proved the most reliable measure of time within their experience4 ,this was something entirely different from the irregular occurrences of earthquakes1 storms1 lightning1 and floods1 not to mention the ravages of beasts and foes4 ,spaces of time that hitherto appeared boundless could be surveyed and computed4 ,the idea of eternity dawned for the first time on humanity4 ,the ,moon was the great master1 measurer of all4 ,in ,sanskrit the ,moon's name is ,ms1 i4 e4 measurer1 and 8mensis0 7,lat4 month7 is closely related to 8mensura0 7,lat4 measure74 ,with peoples who did not live too far from the equator1 the ,moon1 therefore1 took precedence of the ,sun4 ,among the ,mexicans existed1 long ago1 a peculiar unit for measuring long periods of time1 called 8tonalamatl10 comprising #bfj days4 ,it was undoubtedly intended to contain nine synodical months 7reckoned from new ,moon to new ,moon74 ,but such a period would consist of #bfe4eh days and so could not be made to agree with the double decade and was therefore shortened to #bfj days1 as we round off the solar year1 in reality #cfe4bd days1 to an even #cfe days4 ,elaborate studies have been made in order to explain why the ,mexicans chose nine synodical months instead of twelve1 as most other peoples1 but the question has not been solved4 ,this much is certain1 that 8tonalamatl0 has nothing to do with the solar year1 but only with the month4 ,the high age of 8tonalamatl0 is proved by the fact that the priests adhered to it in magic and horoscope casting long after the solar year came into public use4 ,a learned ,mexican1 de ,jonghe1 has pointed out that 8tonalamatl0 was used by all the tribes belonging to the ,nahua-group1 which tribes separated very long ago4 ,this unit of time1 therefore1 bears all the evidence of a very high age1 but is obviously younger than the synodical month4 ,our information in regard to ,moon-worship among the peoples of ,mesopotamia is even more explicit4 ,the ,moon 7,sin7 was rendered homage far earlier than the ,sun 7,shamash74 ,the following translation of a hymn in cuneiform letters ,i quote from ,l4 ,bergstrm1 who published a study on 8,semitic ,moon-,worship0 in ,nordisk ,tidskrift1 #aiji3 ,oh1 ,sin1 thou who alone givest light1 ,thou1 who bringest light to men1 ,thou1 who showest favour to the dark-tressed ones1 ,thy light shines on the firmament1 ,thy torch illuminates like fire1 ,thy radiance fills the wide earth4 ,oh1 heavenly ,anu1 whose insight and wisdom no one comprehends1 ,thy light is splendid as ,shamash1 thy firstborn1 ,before thee prostrate the great gods themselves in the dust ,for on thee rests the fate of the world4 ,anu was god of the heaven and seems here to stand for god in general4 ,sin was father to the daughter ,shamash1 who in this hymn already is considered almost comparable to the father4 ,later on during the ,hammurabi-dynasty 7about #bjjj ,b4,c47 the ,sun1 ,shamash1 was accepted as supreme god1 but the ,moon remained the regulator of time for religious purposes4 ,for astrological forecasts the priests preferred to use the ,moon1 and the 8signs0 in the ,moon were the most important4 ,this is true of astrological prophecies also at the time of ,tycho ,brahe4 8,oh1 ,sin1 thou tellest the oracles to the gods who pray them of thee10 reads an incantation4 ,from ,babylon1 the heart of civilization1 ,moon-worship spread to ,arabs and other ,semites1 and with the ,hebrews1 as ,bergstrm remarks1 the ,moon originally played a far greater part than the ,sun1 although at the time of ,christ the condition was reversed4 ,nevertheless1 the ,moon has still retained its position as chronographer in the ,church ,calendar4 ,in ,psalms #ajd3ai we read3 8,he appointed the ,moon for seasons40 ,in general1 we have built on the belief that the stellar bodies made an impression on men by virtue of the light they radiate and it has therefore been difficult to explain why the ,moon ranked above the ,sun4 ,it is frequently said that the ,sun 7in ,babylonia7 was considered an enemy of mankind as its heat destroyed the vegetation4 7,it is true that a period of severe drought occurs there in the height of the summer47 ,as opposed to this1 the moonlit nights would be considered refreshing and salutary4 ,another explanation is essayed by ,bergstrm1 who says that the luminous ,moon with its ever-changing shape appealed to the imagination of primitive people in a far higher degree than the fairly constantly brilliant ,sun4 ,he is partly correct2 the enormous variation in luminosity from full to new ,moon enables the observer to notice the difference from night to night4 ,the change by about one hour in each twenty-four hours of the time for the rising and setting of the ,moon as compared to the disappearance and reappearance of sunlight1 and more important yet the short periods of the ,moon phases which leave the observations from each receding phase fresh in memory1--both these phenomena contribute toward the high value of the ,moon's synodic revolution as a measure of protracted time duration4 ,the purely practical need dominates1 not1 probably1 any desire to visualize the changes in legends4 ,the ,australian negroes use four different names for the ,moon according to its four quarters1 showing that they1 in all probability1 believe themselves confronted with four different stellar bodies1 just as the ,greeks at the time of ,homer considered the morning- and the evening-star1 i4 e4 ,venus1 as two separate planets4 ,on the other hand1 no ground worth mentioning supports the theory that the scorching heat of the ,sun diminished the peoples' inclination for its worship4 ,on the contrary1 homage was generally rendered to phenomena one feared4 ,it is further not true that the ,babylonians themselves considered the ,sun1 ,shamash1 hostile1 the ,moon1 ,sin1 friendly4 ,the ,sun-god1 ,shamash1 by virtue of his light1 was believed to give life and health4 ,the scorching quality of the ,sun was attributed to another god1 ,nergal1 prince of the underworld1 demon of war and slaughter1 source of fever1 and1 pre-eminently1 of plague4 ,no reason existed1 therefore1 why ,shamash should take second rank after ,sin1 who is said 8to carry water and fire10 meaning1 according to ,schrader1 that he brought fits of ague and fever4 ,when the ,sun after the oppressive day sinks behind the horizon1 it is well known that a sharp fall of temperature occurs1 particularly in arid zones1 but also in humid regions within the tropics where this very phenomenon is utilized for the production of ice4 ,he who exposes himself to the sudden cold of the night falls an easy prey to illness4 ,particularly is this true under a clear sky--primitive people say 8when the ,moon shines0--because of the strong radiation4 ,those who sleep in moonlight are struck by delirium and madness according to primitive thought1 an opinion by no means dead among civilized nations--it is common with seafaring men--and is no doubt the origin of the expression3 moonstruck 7,german3 mondsuchtig1 ,ital43 lunatico1 ,french3 lunatique1 ,swedish3 mnadsrasande1 etc474 ,to this belief has probably contributed the fact that epileptic fits frequently possess a period nearly corresponding to the synodical month1 which1 as ,i have shown elsewhere1 most likely depends on a periodic change in the atmospheric electricity4 ,in this connection it might also be stated that the third among the great star-deities1 ,ishtar1 the queen of heaven 7,astarte1 ,venus71 was the mild but potent1 all-merciful sister in every affliction1 who delivered from sorcery and illness and gave pardon for sin and guilt4 ,this radiant goddess1 who corresponds to the attractive figure of the ,catholics' ,virgin ,mary1 was1 in spite of her solicitude for the afflictions of men1 placed third in the illustrious triad1 ,sin1 ,shamash1 and ,ishtar4 ,the traveller in the desert is certainly often tortured by the severe drought and a consequent insufferable thirst4 ,this1 however1 was justly ascribed to the scarcity of water and not to the ,sun4 ,the ,egyptians1 therefore1 wished that their departed ones on the journey to their new dwelling-places would meet with refreshing springs where they might quench their thirst and northerly winds that might cool the air4 ,it is well known that the ,mohammedans have formed similar conceptions of a paradise in life to come4 ,entirely new conditions arose when the population grew until agriculture became a necessity for the production of sufficient food4 ,the influence of the ,sun now became so dominating that it must be given the first place among the powers that affect the fates of men4 ,the plants have a decided annual period and so have the overflows of the rivers which were of the utmost importance in those countries where the cradle of civilization stood4 ,the rainfalls themselves were of annual recurrence as were also the intervening droughts4 ,in ,egypt the great importance of the floods caused the introduction of the solar year at a very early stage and its length was fixed at #ab months of #cj days1 or #cfj days1 so that the beginning of the year occasionally had to be adjusted4 ,this was accomplished by resorting to observations of the rising and setting of the ,dog ,star or ,sirius4 ,thus we realize how difficult it was to determine the exact length of the solar year from everyday phenomena4 ,the great reformer ,amenhotep ,,iv4 endeavoured about #adjj ,b4,c4 to have the ,sun-god recognized as sole master of all the world4 ,he met1 however1 with such great obstacles on the part of the conservative priesthood1 which as they largely were serving different gods would have lost part of their power if the reform had prevailed1 that his successor was obliged to yield to the solid opposition4 ,in ,babylon the local god ,marduk1 once representative of the planet ,jupiter1 and among the star-gods ranking next to the three ,super-gods1 became about #bjjj ,b4,c4 elevated to the highest position among the gods and assumed at the same time the dignity of ,sun-god4 ,it may here be mentioned that ,marduk also played a great part as healer of illness4 ,the evolution in ancient ,rome followed the same course although at a far later time4 ,emperor ,aurelianus 7#bgj-bge ,a4,d47 under the influence of oriental ,mithras-cult elevated the ,sun-god to supreme god of the whole ,roman ,empire1 which then comprised almost the entire known world4 ,especially significant is the fact that ,venus with the ,mexicans played as important a part as did the ,moon and the ,sun4 ,the luminosity of ,venus1 unlike that of planets outside of the earth's orbit1 but like that of the ,moon1 changes from a maximum1 intense enough in the tropics to throw a shadow1 down to a minimum which approaches complete darkness4 ,its period is closely #a4f years4 ,it falls short of this figure by about two hours and the ,mexicans therefore introduced a correction similar to the bissextile day in our leap year1 of one day in every twelve years1 which day1 however1 had to be deducted instead of added4 ,observations of the changing luminosity of ,venus and of its position relative to the ,sun obviously lent themselves admirably to measurements of long periods of time and particularly to determination of the length of the important solar year as five ,venus-periods very nearly equal eight solar years4 ,the ,mexican priests established the fact that #ajd solar years correspond to #fe ,venus-periods or #adf 8,tonalamatl40 ,star-cult was as strongly developed in ,mexico as in ,babylon4 ,its main doctrine is stated by ,alfredo ,chavero thus3 8,the ,father-,creator was ,heaven1 ,xiuhtecutli1 or the ,azure-blue master4 ,the mother was ,omecihuatl1 the ,milky ,way1 or the dual mistress40 ,it is well known that a large part of the ,milky ,way1 from the 8,swan0 to the neighbourhood of the ,southern ,cross1 is divided in two parallel branches1 which fact probably is responsible for the title1 the 8,dual ,mistress40 8,heaven influenced the ,milky ,way through fire2 from its cosmic matter the stars were set free1 the most prominent of which were ,tonatiuh1 the ,sun2 ,tezcatlipoca1 the ,moon2 and ,quetzalcoatl1 ,venus4 ,these were made the supreme gods4 ,for the purpose of worship1 they were symbolized in human shape4 ,myriads of images1 representing these star-gods1 were modelled in clay1 wood1 or stone40 ,according to this remarkable picture the ,mexicans should have arrived at a far better solution of the world-riddle than even the ,babylonians did4 ,while most other peoples assumed heaven and earth as the original principles1 they gave the high position of progenitress of all to the ,milky ,way4 ,from her the innumerable stars1 with the ,sun in the lead1 issued4 ,this agrees to a considerable extent with the present conception which we have arrived at during this very last decade1 principally thanks to the work of ,american astronomers4 ,their investigations have shown how the stars are segregated from the nebulous primeval matter of the ,milky ,way2 how they add distance between themselves and their matrix with age1 while simultaneously they develop an increasing individuality4 ,we have seen that ,venus-,ishtar was honoured with membership in the august triad of star-gods1 also among the ,babylonians4 ,their successors1 the ,assyrians1 retained the inherited traditions4 ,thus their kings in the ninth century before ,christ symbolized their divine lineage by wearing a necklace with a moon-crescent in the middle1 a cross in a ring1 emblem of the ,sun1 on one side1 and on the other a star1 emblem of ,venus 7compare ,montelius1 ,nordisk ,tidskrift1 #aijd1 p4 #ac1 fig4 #cj74 ,the ,jewish synagogues are generally decorated with the star-emblem4 ,the ,mohammedans1 like the ,jews1 utilize the position of the ,moon for determination of the ,church calendar1 and we employ the same means for fixing ,easter time4 ,the ,mohammedans reckon with a year of #ab synodical months4 ,twelve such months contain only #ced4d days while a solar year comprises #cfe4bd days1 and as a rule1 therefore1 the synodical month was rounded to #cj days instead of #bi4ec and the solar year to #cfj days4 ,such was the arrangement in ,egypt and originally also in ,babylon4 ,primitive men comprehend fractions only with extreme difficulty4 ,in order to correct the discrepancies1 odd months were introduced about every sixth year4 ,from this time we may trace the high reputation of the number twelve4 ,the ,zodiac was divided into twelve houses in each of which the ,sun was to dwell a month at a time4 ,day and night were each divided into twelve hours4 ,the circle was divided into #cfj degrees corresponding to the number of days of the year1 so that the position of the ,sun at noon should proceed one degree of the heaven from day to day4 ,as the ,moon dominated chronometry1 a complication which must have caused considerable confusion was in many places introduced4 ,we have seen that the ,australian negroes gave four different names to the ,moon in its four different phases4 ,the great change in appearance of the ,moon from quarter to quarter makes such a division natural4 ,the synodical month was therefore made to consist of four parts1 called weeks4 ,as the length of a month is #bi4ec days1 the nearest number evenly divisible by four1 namely #bh1 was substituted1 and so seven days were allotted to each week1 thus introducing an error of not less than #e4e4 ,to the establishment of this week the assumption of seven wandering stars has no doubt largely contributed4 ,the priests had discovered that besides ,sun1 ,moon1 and ,venus1 four other stars shift their position on the firmament with reference to the fixed stars1 which latter appear always to maintain their relative distances4 ,these four wandering stars were ,mercury1 ,mars1 ,jupiter1 and ,saturn4 ,each day in the week was dedicated to one of the seven wandering stars and received its name4 ,these names have been maintained to the present day1 for instance1 ,sunday1 the ,sun's day1 ,monday1 the ,moon's day1 etc4 ,the lunar calendar1 established through religious considerations1 supplanted the more rational one1 which latter1 however1 survived in ,egypt1 and was reinstated in the ,occident during the ,french revolution1 although unfortunately only for a short time 7#agic-ahje74 ,as a result1 the synodical month1 in order to suit the calendar1 has been changed not only with half a day to thirty days1 but also with one and a half days to twenty-eight days4 ,if decades had been adhered to we would have had months of even thirty days and either five leap months of thirty-one days each 7during leap year six7 or half a decade interpolated at new year4 ,besides the seven wandering stars known to antiquity 7at present over eight hundred planets have been observed71 several other stars and constellations played an important part4 ,the ,magellanic clouds1 considered of evil nature1 and the ,pleiades appealed already to the ,australian negroes4 ,in the northern hemisphere1 where the opportunity of observing the ,magellanic clouds is small1 situated as they are near the ,south ,pole1 the ,pleiades have attracted the greater attention and the ,phnicians especially appear to have taken interest in this constellation4 ,from them1 reverence for the ,pleiades spread to a large part of ,africa1 where we now to our surprise find this star cluster reproduced along with symbols of ,sun1 ,moon1 and ,venus4 ,homer also mentions the ,pleiades and a few other constellations1 namely1 the ,hyades1 ,orion1 the ,great ,bear1 and the stars ,sirius and ,arcturus4 ,at all events1 the ,pleiades have frequently occupied a unique position in the old world4 ,sirius1 the brightest star in the heavens1 and ,canopus1 the second in brightness1 also belonging to the southern hemisphere but only half as far removed from the ,south ,pole as ,sirius1 have both evoked the attention and the worship of the primitive people1 in this case the ,south ,africans4 ,at length1 the nations1 particularly the ,babylonians and the ,mexicans1 acquired a wider knowledge of the different stars4 ,as the most important ones1 ,sun1 ,moon1 and ,venus1 guided the seasons and hence all natural phenomena1 a certain mundane significance was naturally ascribed also to the younger ones4 ,not only seasons1 months1 days1 and hours were each ruled by its star1 but so was everything in nature2 different winds1 provinces1 trades1 bodily organs1 animals1 persons1 each possessed its star and celestial protector4 ,comprehensive studies of these correspondences and connections were made and the conclusions were drawn from immaterial semblances and often wholly arbitrarily1--as regards persons from the configuration of the stars at the time of birth4 ,thus grew an enormously extensive collection of correspondence- and sympathy-doctrines accompanied by a detailed symbolism1 an entire quasi-science1 which must never be questioned as it originated with the infallible priests4 ,with the ,babylonians1 religion and science completely melted together and even art was entirely subservient to the same interests4 ,occasionally the loss of this blissful state draws forth a sigh4 ,fortunately it is gone never to return4 ,the oriental wisdom was brought over to ,greece and was there amalgamated with the ,platonic-,aristotelian philosophy4 ,in this form the ,babylonian heritage held sway over the thought of mankind up to less than #bjj years ago4 ,the most important branches of this fanciful1 so-called science were astrology and alchemy4 ,tycho ,brahe himself made it the object of his life to strengthen astrology by contributing new material to it4 ,kepler is said not to have believed in astrology but he nevertheless cast horoscopes not only for princes and persons of high position in order to improve his economy1 but also for his own family4 ,probably traces of the old superstition clung to him1 and presumably he thought3 8,if it does no good1 neither does it do any harm40 ,in the same manner1 alchemy was carried on by faithful adepts1 but more often by impostors1 seldom averse to 8occult0 sciences4 ,astrologers and alchemists exist even yet among the numerous devotees to occultism2 at high price many of them make their predictions or sell their secrets4 ,i have heard a ,swedish engineer of very high standing state that their prognostications agreed with events4 ,among the few alchemists in ,europe1 most of whom seem to be religious visionaries1 ,strindberg is of a certain interest to us4 ,correspondence-theory has played a very large part in the speculations of the learned up to comparatively recent time4 ,it is utilized extensively in the later fantastic writings of ,swedenborg4 ,numerous traces are to be found also in the weakest works of ,strindberg4 ,the renowned ,french chemist1 ,berthelot1 has given a valuable analysis of the alchemist's method of treating chemical phenomena4 ,his general conclusion is that the false principles which led the alchemists astray revert back to ,plato's and ,aristotle's philosophical theories regarding the composition of matter4 ,something similar can be said of astrology4 ,it plays with ideas of its own fabrication with hardly any foundation in reality4 ,the result is almost wholly without value4 ,the greatest astronomer in ,babylon1 ,kidinnu 7about #bjj ,b4,c471 constructed tables of great accuracy giving the position of the stars4 ,in this work he utilized observations gathered over thousands of years4 ,these ephemerides were also intended as scripture source for reading the fate of men and for determination of the auspicious moment for the commencement of an undertaking4 ,at all events1 they placed great revenue and power over souls in the hands of the ruling priesthood4 ,it does not appear that these priests were able to rise to an attempt of a physical explanation as to the nature of the stellar bodies4 ,that was probably also considered dangerous4 ,the stars were deities composed of purer and more refined matter than found on ,earth4 ,it were not improbable that the gods would inflict vengeance on the presumptuous one who dared to intrude upon their secrets and pass judgment on their peculiarities4 ,fortunately1 there existed in ,greece another tendency in philosophy besides the scholastic and the ,platonic-,aristotelian4 ,but this was mainly represented in southern ,italy1 ,sicily1 and later in ,alexandria4 ,already the followers of ,pythagoras had made important progress toward a solution of the stellar problems4 ,the crowning point was reached by ,aristarchos from ,samos1 who lived in ,alexandria about #bajj years ago4 ,he established #agjj years before ,copernicus the heliocentric system4 ,it is often said that his work was of little value1 as ,copernicus nevertheless must do it over again4 ,it is then forgotten that ,copernicus himself cites the philosophers of antiquity who expressed theories in agreement with the heliocentric system and expressly states that he was bold enough to advance his hypotheses because so many prominent authorities could be mentioned who favoured them4 ,copernicus did not dare entirely to break away from the ,ptolemaic system1 and was inconsistent enough partly to use it in his calculations of the motions of the stars4 ,we have lately advanced farther along the road of ,pythagoras and ,aristarchos1 of ,copernicus and ,galileo1 and we have perfected their methods to a high degree4 ,progress in astronomy and kindred sciences is nowadays made at a dizzying speed if measured with the standard of antiquity4 ,occasionally we hear a warning voice asking us to show more deference to a philosophy directly descending from the ,platonic-,aristotelian4 ,he who is at all familiar with the history of natural science will understand us when we answer3 8,we have had more than enough thereof40 ,that non-naturalists sometimes have a peculiar conception of the present status of astronomy is well illustrated by the statement of one of our foremost theologians in a review of a popular astronomical work where he remarked that the astronomer of today had not advanced much beyond those of ancient time who also could forecast eclipses of the ,sun4 ,the predictions were then founded on the recurrences of eclipses after regular intervals much as the new ,moons were foretold1 with the difference only that the latter occur much more frequently4 ,our knowledge of the stellar bodies at present and fifty or sixty years ago are a world apart and the same is true of the latter and that of antiquity4 ,but we must not therefore forget that our brilliant star-science today is derived from men's desire to measure time1 and particularly from their need to foresee the food supply in coming days4 ,,chapter ,,ii ,,the ,,riddle ,,of ,,the ,,milky ,,way ,during dark but starlit nights1 the gorgeous firmament is decorated with an irregular band of light that describes a winding path across the heavens4 ,it continues also in the quarters hidden from our sight so that it may be said to surround the firmament like a girdle4 ,this band1 which is most luminous in the ,northern ,hemisphere1 is called 8,the ,milky ,way40#a ,it forms an angle with the equator of about #fj and divides the firmament in two nearly equal parts--the northern1 however1 is slightly larger4 #a ,the literal translation of the ,swedish name is 8,the ,wintry ,way40 ,the ,milky ,way1 no less than other stellar phenomena1 attracted the early attention of the people4 ,the ,dieri ,tribe in ,central ,australia says that the ,milky ,way is the stream of heaven and the ,mexicans consider it the source of all that is4 ,tradition endeavoured to explain its origin4 ,its milky appearance caused the ,romans to call it 8,via ,lactea10 a name that is retained in translated form in most modern languages4 ,this name is coupled with the legend of the ,hercules-child1 who sucked the breast of ,juno and when it was pushed away by the incensed goddess1 the milk was spread across the sky4 ,nevertheless1 the human race1 until about two hundred years ago1 had little conception of the extraordinary importance of the ,milky ,way4 ,anaxagoras and ,democritos surmised1 however1 that it consists of a collection of exceedingly minute and densely clustered stars each of which has the nature of our ,sun4 ,ptolemy described1 nearly two thousand years ago1 its position on the firmament and his observations are valid today as far as determinations with the naked eye suffice4 ,when ,galileo introduced the telescope1 the conception of the ,milky ,way as made up of innumerable stars was verified4 ,not quite two hundred years ago ,swedenborg1 in his cosmological speculations1 considered our solar system as a part of the ,galaxy4 ,wright1 ,kant1 and ,lambert further amplified these theories4 ,the first important forward step was taken by the great ,william ,herschel in his statistical researches4 ,he demonstrated that the stars lie closer to each other the nearer the ,milky ,way they are located4 ,this is mainly true about the small stars invisible to the naked eye while the more luminous ones are more evenly distributed over the heavens4 ,in certain parts of the ,milky ,way the stars are over one hundred times more crowded than at its poles--that is1 the points farthest removed from the ,galaxy4 ,herschel's investigations were continued and elaborated by ,struve1 and later by numerous other scientists4 ,through these researches1 it has been determined that the ,milky ,way is1 so to speak1 the foundation upon which the star system1 visible to us1 is built4 ,all kinds of stellar bodies have been studied and their distribution has proved to be symmetrical with reference to the plane of the ,galaxy4 ,the majority is greatly concentrated around the ,milky ,way4 ,to these belong the new stars which occasionally blaze into existence1 as the well-known new star in ,perseus1 #aija1 and nearly all of which have appeared in the ,milky ,way or in its immediate vicinity4 ,we also find there the irregular nebul1 enormous1 vastly diffused volumes of gas1 among which the best known is the ,orion nebula1 and which seem to constitute the primeval matter out of which the stars are born4 ,we might further mention the star-clusters1 dense1 ball-shaped agglomerations of stars1 and the so-called planetary nebul1 which--at least in their visible outer shell--also consist of gas accumulations with a spherical or ellipsoid conformation4 ,the numerous spiral nebul on the other hand1 those strange stellar bodies to which we later shall have occasion to return1 are beyond comparison more frequent in the regions surrounding the poles of the ,galaxy than in the rest of the heavens4 ,many astronomers have considered the ,milky ,way itself a nebula4 ,the most common theory doubtless is that it closely conforms to a spiral nebula--an opinion that has found a particularly warm advocate in the ,dutch astronomer1 ,easton 7see ,figure #a74 ,a few years ago ,prof4 ,bohlin expressed the view that it is most akin to a planetary nebula1 or more precisely to a ring nebula which is supposed to grow out of a planetary ellipsoid nebula by the gaseous matter being driven from its poles toward its equator4 ,it is of a certain interest that this theory lends itself to the support of ,swedenborg's--nevertheless improbable--hypothesis about the origin of the planets in the solar system4 ,as we later shall see the ,easton conception has the better reasons in its favour4 ,if classified according to age the stars are again distributed with the ,milky ,way as a reference point4 ,thus1 let us consider their evolution1 which for various reasons is assumed to take the following course4 ,we may commence when the star-matter existed on the nebula stage4 ,it then radiated the light characteristic of certain incandescent gases1 principally the lightest two1 hydrogen and helium1 and further of an otherwise unknown gas called nebulium 7nebula-substance74 ,these gases were later condensed and dark spectral lines commenced to appear beside the bright lines of the aforesaid gases4 ,stars on this stage1 named after their discoverer ,wolf-,rayet stars1 occur only in the immediate vicinity of the ,milky ,way4 ,a later stage in their evolution is represented by the so-called helium stars in whose spectrum the dark helium lines preponderate4 ,they are considerably concentrated around our ,galaxy4 ,somewhat more evenly distributed and yet of decidedly greater frequence in the neighbourhood of the ,milky ,way1 the hydrogen stars appear1 characterized by strongly developed hydrogen lines and somewhat retreating helium lines4 ,these stars are more developed than the helium stars and form with them the group of white stars so named after the colour of their light4 ,next in evolution follow the yellow stars1 to which our ,sun belongs4 ,dark metal lines appear in their spectrum4 ,they are more evenly distributed than the groups mentioned before4 ,still further is this true about the red stars whose spectra contain the characteristic bands of chemical compounds and therefore betray comparatively advanced cooling4 ,they are fairly uniformly spread over the heavens but are still somewhat more numerous in the vicinity of the ,milky ,way than further therefrom4 ,illustration3 ,fig4 #a4 ,the ,milky ,way1 pictured as a spiral nebula by ,easton ,these facts are demonstrated in the statistics by ,e4 ,c4 ,pickering1 ,director of the ,harvard ,observatory1 who divided the firmament in four equal zones1 the first of which is nearest to the ,milky ,way 7and includes it7 and the last of which contains the ,galactic poles4 ,his table shows the percentages of different stars in each of the four zones4 ,white ,galactic ,helium ,hydrogen ,yellow ,yellow ,red ,latitude ,stars ,stars ,stars ,stars ,stars ---------------------------------------- ------------------- #h4a #ea4b #cg4d #bi4g #bi4d #bf4g #ba4f #ca4g #bh4f #bg4i #bf4g #bg4f #ci4h #aa4i #ah4c #ba4a #ba4i #bc4f #fb4c #e4b #ae4g #ba4c #bb4j #bb4a ,number of stars observed #gaf #ahhe #acbi #agai #deg ,the difference is most pronounced in the two first groups2 in the three last it is small but unmistakable4 ,an even distribution would correspond to #be per cent4 in all four divisions of the heavens4 ,these comprehensive statistics1 embracing #fajf stars1 seem to indicate that the stars in their first stage were within the ,milky ,way but subsequently drifted away with increasing age4 ,this leads us to the thought that they originated from the irregular1 nebulous accumulations which occur in the ,milky ,way and in its vicinity1 or more correctly from similar formations which formerly existed in these regions but which now have clustered into stars4 ,this agrees very well with another observation4 ,with the help of the spectroscope the motion of different stars has been determined with reference to the point where the sun now is4 ,the velocities have been found greater the older the stars are as shown in the table below taken mainly from the investigations of the renowned astronomer1 ,campbell4 ,mean velocity of3 ,irregular nebul #j ,km4 7 #j ,miles7 per sec4 ,wolf-,rayet stars #d4e 0 7 #b4h 0 7 0 0 ,helium stars #f4e 0 7 #d4j 0 7 0 0 ,hydrogen stars #aa 0 7 #f4h 0 7 0 0 ,yellow stars #ae 0 7 #i4c 0 7 0 0 ,red stars #ag 0 7#aa4e 0 7 0 0 ,planetary nebul #be 0 7#ae4e 0 7 0 0 ,to these figures a few remarks founded on recent observations might be made4 ,the average distance between us and the stars in each group is different and the yellow stars1 to which indeed our ,sun belongs1 are those nearest to us in space4 ,they are therefore easier to observe than stars in the other groups4 ,campbell's statistics include also for this reason a smaller number of stars in this class than in the others4 ,it is conceivable and by the astronomer ,halm held to be true that the mean velocity of the smaller stars is greater than that of the larger ones4 ,this is the condition existing in a mixture of different gas molecules1 with which the brilliant ,french scientist1 ,henri ,poincar1 compared the throng of stars1 inasmuch as the heavier molecules possess the slower motion4 ,to confirm this ,w4 ,s4 ,adams of the ,carnegie ,observatory on ,mount ,wilson compared stars of equal velocity in their own orbits4 ,such stars are considered to be on the average equally far removed from us4 ,he found the theory of ,halm confirmed4 ,the mean velocity of the hydrogen stars was reduced from #aa km4 7#f4h miles7 to #g4e km4 7#d4g miles71 that of the yellow stars from #ae km4 7#i4c miles7 to #i4b km4 7#e4h miles71 and that of the red stars from #ag km4 7#aa4e miles7 to #ad km4 7#h4g miles71 while that of the helium stars remained unchanged4 ,the sequence of the stars arranged according to velocity in the line of sight is evidently not modified by this new calculation4 ,in regard to the motion of the planetary nebul it should be mentioned that ,campbell in this connection has carried out a great number of new determinations according to which the mean observed velocity of these large bodies in the line of sight must be increased to not less than #db km4 7#bf miles7 per second4 ,campbell and ,moore contribute the following interesting data in regard to ,nebula ,n4 ,g4 ,c4 #gjji 7,fig4 #b73 8,measures of the rotational velocity of the nebula enable us to draw some interesting conclusions concerning its mass4 ,on the most plausible assumption as to the location of the axis of rotation the orbital speed of the nebular materials lying at a distance of #i seconds of arc from the centre is about #f km4 7#c4g miles7 per second4 ,if we provisionally assume the mass of the central nucleus to equal that of the ,sun1 ,kepler's law connecting the periodic time with the distance from the nucleus tells us definitely that the nebula is distant from us only #h4i light years4 ,this must be regarded as an improbably small value1 in view of other evidence bearing on the question4 ,for assumed distances of #ajj and #ajjj light years1 which we have reason to believe are more probable orders of nebular distance1 the masses of the nebula would be respectively #aa4c and #aac times that of the ,sun1 and the corresponding periods of rotation #acga and #ac1gaj years4 ,from these considerations it seems certain that the mass of the planetary nebula ,n4 ,g4 ,c4 #gjji is several times that of the ,sun4 ,the nebula is therefore competent1 from the point of view of its mass1 to develop into a system more pretentious than is our solar system4 8,a few speculations concerning this nebula may not be without interest and value4 8,the faint extensions to the east and to the west of the elliptical figure suggest an encircling ring of materials whose principal plane1 passing through the nucleus1 passes also near our 7the observers'7 position in space4 ,these extensions terminate in condensed nuclei at equal distances from the nucleus and on exactly opposite sides of the nucleus4 ,the faint extensions and condensations may be and probably are largely the effect of the edgewise projection of such a ring1 as in the case of ,saturn's rings when the observer is in the plane of the rings4 ,the forms of the two terminating condensations1 and especially the wing extending up and out from the east condensation1 suggest that we are not precisely in the plane of the assumed ring4 8,the form of the main nebula appears to be ellipsoidal and not chiefly elliptical4 8,the space immediately surrounding the central nucleus appears to be relatively vacuous4 ,aside from the nucleus1 the principal mass of visible nebulosity exists in the brilliant ring1 roughly elliptical as to its inner and outer boundaries1 which occupies the region about midway between the nucleus and the outer edge of the nebular structure4 ,the brilliant ring is probably in reality an ellipsoidal shell2 the projection of such a shell upon a plane at right angles to the line of sight would naturally show a relatively dark central area1 but the projection principle may not be the only one involved4 8,if this nebula is in process of development into a solar system1 the indications are for a system having certain resemblances to our solar system4 ,our four outer planets have a combined mass #bbe times as great as that of the four inner planets4 ,similarly in ,n4 ,g4 ,c4 #gjji1 there is apparently a paucity of material to form planets near the nucleus and an abundance of material for planets at greater distances from the nucleus40 ,illustration3 ,fig4 #b4 ,planetary nebula ,n4,g4,c4 #gjji 7composite drawing1 from ,curtis's photographs of the nebula made with the ,crossley reflecting telescope4 ,the scale is in seconds of arc74 ,from ,proceedings of the ,national ,academy of ,sciences of ,u4 ,s4 ,a4 ,interesting observations have been presented recently also with reference to the largest among the irregular nebul1 namely the ,orion nebula4 ,three astronomers in ,marseilles1 ,bourget1 ,fabry1 and ,buisson1 found that parts of this nebula1 in the neighbourhood of the so-called trapeze and very close to each other1 moved with different velocities and that this difference might amount to #aj km4 7#f4b miles7 per second4 ,the south-easterly part approaches us while the north-easterly recedes from us4 ,consequently a violent whirl-motion undoubtedly takes place in this region4 ,this observation has been verified by the well-known ,chicago astronomer1 ,frost1 who employed a different method of investigation than his predecessors4 ,he noted differences in velocity amounting to #aa km4 7#f4h miles7 per second between points not over two seconds of arc distant from the trapeze4 ,if therefore we say that the irregular nebul on the average possess no motion1 this statement does not preclude important local deviations from the rule within the nebul1 intimating a transformation which probably leads to the concentration of the nebulous matter toward the centre of the whirl4 ,leaving out1 to begin with1 the planetary nebul1 it appears that the original matter of the stars stands still in space1 that their average velocity increases with increasing age and approaches a mean value of about #ah km4 per second or roughly #ajjj times the speed of the ordinary passenger train4 ,our ,sun1 in particular1 moves with a velocity of #bj km4 7#ab4d miles7 per second toward a point in the constellation ,hercules #cj degrees north of the equator4 ,what force then shall we say it is that causes the motion of the stars8 ,as far as we know none but gravitation4 ,it appears therefore as if the gaseous primeval substance of the stars were not governed by this force4 ,it might prove hazardous1 however1 to make this assumption as gases also possess weight and even the most rarefied strata of the ,earth's atmosphere exert barometric pressure by virtue of their attraction to the mass of the earth4 ,rather the immobility of the nebul is due to the frequent collisions between the molecules in any quantity of gas even if it be attenuated to such a high degree as in the nebul4 ,thus1 the molecules strike a balance1 as it were1 against each other so that the different parts of the gas accumulations shortly are brought to rest relative to each other4 ,the irregular gas mists around the ,milky ,way form therefore a continuous whole4 ,a different condition obtains in regard to condensed stellar bodies such as the stars4 ,they may in the densest throng move during billions of years before they collide2 but they might on the other hand enter nebulous masses and thereby suffer gradual retardation4 ,we now refer to stars moving outside of the vapour clouds4 ,they are therefore unrestricted and the longer they have obeyed gravitation without impeding encounters with nebulous matter1 in other words the longer the time elapsed since they emerged from the gas accumulations which gave them birth1 the swifter is their motion4 ,their 7average7 velocity can of course not exceed a certain limit which in our parts of the universe appears to be about #ah km4 7#aa4b miles7 per second4 ,campbell's measurements show that for the youngest stars 7all except the red7 the velocity is greatest in the plane of the ,milky ,way1 a natural enough condition as the attracting matter here is most abundant4 ,the planetary nebul possess a greater velocity although they1 as consisting of mist vapours1 are in the first stage of evolution4 ,faster yet do the spiral nebul move according to measurements by ,wolf of ,heidelberg4 ,this shows that they are of a different nature from the irregular nebul1 which form the matrix of the ,milky ,way4 ,a closer examination of the few--thirteen in all--planetary nebul1 determined by the ,american astronomer ,keeler1 convinced me that they approach the ,galaxy from its poles with a moderate speed1 and subsequently under the influence of its attraction curve their orbit1 rapidly gain in velocity1 and finally rush into the nearest part of the ,milky ,way with a very high speed4 ,a great number of them are no doubt caught in the mists or star-throngs of the ,milky ,way after exposure to numerous collisions and sweeping away all matter in their course4 ,such clean-swept traces are very common in the area of the ,milky ,way4 ,one of the most beautiful examples is the so-called ,cocoon nebula in the constellation ,cygnus 7the ,swan74 ,it has left in its wake a dark rift1 in whose bottom1 however1 exceedingly small and evidently very remote stars are visible according to the ,german astronomer ,wolf 7see ,worlds in the ,making1 page #agb1 ,fig4 #ee74 ,the great mean velocity of the planetary nebul indicates that they originally did not belong to the ,galactic system1 a conclusion also reached by ,bohlin1 but for other reasons4 ,they are nevertheless more abundant in the neighbourhood of the ,milky ,way than in other parts of the heavens4 ,this fact1 if viewed superficially1 might lead to the belief that they are indigenous to the ,galactic system1 but is explained by their concentration in obedience to gravitation toward the ,milky ,way4 ,quite recently 7#aiag7 ,van ,maanen determined the distance of one of these highly interesting celestial bodies1 tabulated in the ,new ,general ,catalogue as ,no4 #gffb4 ,its distance was found to be only about #adj light years4 ,this is about sixteen times the distance of ,sirius and the mean distance of a star of the fifth magnitude4 ,this circumstance agrees very well with the idea that this nebula is captured by the ,galactic system to which it has approached from very distant parts of the space outside of the ,galactic system4 ,one of the most remarkable astronomical discoveries in recent years was made by ,kapteyn1 who thereby as well as by other achievements has gained perhaps the highest rank among astronomers of today4 ,he has shown that the stars rushing forth in the neighbourhood of the ,sun belong to two great groups1 one coming from the constellation ,orion1 and the other at nearly a right angle 7#ajj7 from the constellation ,scorpio4 ,in the former1 we find nearly all the helium stars hitherto studied4 ,we have previously seen that these stars stand almost still with reference to the ,galaxy while the irregular nebul possess no motion at all relative to the same reference point--and the ,galaxy is the natural datum-line for all astronomical measurements--so that the motion of the first-mentioned star-group toward the ,sun is principally due to the ,sun's own motion4 ,this group1 according to ,kapteyn1 obeys the law of relative star velocities even better than the combined world of all stars2 thus with reference to the ,sun1 the helium stars are the slowest1 the yellow stars the fastest1 while the hydrogen stars occupy a middle position1 all a self-evident consequence of their own velocity with reference to the ,galaxy which increases from helium stars to yellow stars4 ,kapteyn has shown another regularity in this group which is easily explained4 ,we have previously mentioned that the yellow stars are most1 the helium stars least removed from their place of birth in the ,milky ,way4 ,the result is that the yellow stars appear 7on the average7 to come from a point farther from the ,galaxy than the apparent origin of the hydrogen stars and more remote yet than that of the helium stars4 ,on account of the relatively high velocity of the yellow stars in different directions1 their stream appears to be more divergent than the stream of hydrogen stars1 and helium stars move in almost parallel paths 7nearly directly opposed to the ,sun's true motion with reference to the ,galaxy74 ,similar regularities have been found by ,kapteyn in the second star-drift which would lead us to think1 as indeed ,kapteyn assumes1 that these stars also developed from an original nebulous mist1 which arrived in our neighbourhood from the unknown distant1 but is now used up in the formation of corresponding stars4 ,here again the yellow stars should have departed farther from their matrix than the white hydrogen stars4 ,helium stars are very rare in this drift1 so that no reliable statistics have as yet been made for them4 ,it has been one of the most difficult problems of cosmogony to form a theory to account for the origin of the ,galactic system4 ,we may1 almost yearly1 witness how new stars blaze into existence only to fade rapidly and in a few years return to their old insignificance--that is1 they become invisible to the naked eye although through powerful lenses we may frequently discover an exceedingly faint star in their position4 ,as a rule1 a nebula of the planetary type is formed in the course of a few months4 ,somewhat later the nebula is transformed into a ,wolf-,rayet star4 ,it is interesting to note that ,wright found the central bodies in certain planetary nebul to be ,wolf-,rayet stars4 ,we have good reasons to assume this blazing forth into light to signify the collision of two faintly luminous or possibly extinct stars4 ,the new lights appear also in stellar regions where the star density is very great1 particularly in the ,milky ,way or its vicinity4 ,we see therefore repeatedly how mists with enclosed central stars originate4 ,they remind us to a certain extent of the ,galaxy with its clouds and stars and along the road thus suggested trials have been made to reach the solution of the riddle4 ,the difficulty lies in the fact that the orbs whose collision create 8new stars0 are small1 probably smaller than our ,sun1 while the mass gathered in the ,milky ,way most likely is trillions#b of times greater than that of the ,sun4 ,it is true that we know a few unique stars1 such as ,arcturus1 which exceed our ,sun in size several tens of thousand times1 but not even two such stars would account for the mass of the ,galaxy1 and furthermore the probability that two stellar bodies of such rare dimensions would collide is so very small that it must be left out of account4 #b ,american and ,french numeration2 billions acc4 to ,swedish and ,english usage4 ,kapteyn's star-drifts1 containing many thousands or probably millions of stars1 appear to furnish the bridge that leads to the solution of the riddle of the ,milky ,way4 ,these drifts were once enormous gas-clouds1 in mass probably several million times greater than that of the ,sun4 ,they also had an extension equal to trillions of stars4 ,the probability for the meeting of two such gas-drifts is comparatively large and should not be much smaller than for the entrance of a star-drift into the ,milky ,way1 an occurrence which actually has happened as shown by ,kapteyn4 ,when two such enormous gas-clouds meet1 each with a cosmic velocity of about #bj km4 per second1 a long time would not elapse before the gas molecules in the region of interpenetration would be retarded in their original motions4 ,an extraordinarily strong concentration and heating would occur in this territory1 which is surrounded by the comparatively cold and heavy masses which remain unaffected because outside of the impact-area4 ,a certain degree of equalization would naturally take place in the layers adjoining the boundary between active and inactive parts and the former would1 furthermore1 be set into a rapid spin around an axis perpendicular to the plane containing the two original motions4 ,on account of the great viscosity of gases1 particularly at high temperature1 the central part would rotate as a coherent unit4 ,thus it would form a disk of gaseous matter4 ,this disk would be thickest in the middle and would become thinner toward the edge where centrifugal force acts most powerfully4 ,illustration3 ,fig4 #c4 ,n4,g4,c4 #deid4 ,exposure #b hours4 #amm #f0g4 ,from ,proceedings of the ,national ,academy of ,sciences of ,u4 ,s4 ,a4 ,such a discous nebula has been investigated by the astronomer ,f4 ,g4 ,pease of the ,carnegie ,observatory on ,mount ,wilson4 ,by means of the spectroscope he has studied the motion of ,nebula ,no4 #deid in the ,new ,general ,catalogue 7see ,fig4 #c74 ,this body is believed to be a spiral nebula like those in ,figs4 #d and #e but viewed from the side so that the spirals appear as a band4 ,as the picture shows1 this band is coursed through by a thick dark line1 owing1 it is believed1 to a cold non-luminous dust-cloud outside of the spiral4 ,the bright band is broadest in the centre4 ,the curvature of the dark middle line in the shape of an arc1 whose apex points downward1 combined with the fact that the major portion of light falls above this arc1 indicates that we do not view the nebula exactly on edge but from the upper 7north7 side of a plane through the arms of the nebula4 ,the nucleus speeds away from us at the dizzying rate of #aahj km4 7#gcj miles7 per second4 ,the east edge1 i4 e4 the left on the picture1 departs with the still higher velocity of #afcj km4 7#aajj miles7 per second1 while the west 7right7 edge retreats at the rate of only #hjj km4 7#die miles7 per second4 ,according to ,pease1 the nebula rotates as a solid disk so that the difference between the velocity of any point and that of the centre increases in the same proportion as the distance of the point in question from the centre4 ,it is probable that we have been prevented from observing the outer parts1 corresponding to the spiral arms proper1 by the ring of dust which encircles the nebula4 ,the visible portion occupies an arc of #b minutes on each side of the centre4 ,its spectrum corresponds to that of star-group ,f-#e among the yellow stars in the ,harvard classification4 ,therefore1 it is not the light of the coherent gas-cloud which preponderates but rather that of the stars consolidated within the cloud1 and corresponding to the stars in the ,milky ,way4 ,this star-light is so bright that it entirely suppresses the radiation from the gas-cloud itself4 ,such parts of the gas-aggregation as are most removed from the place of collision continue in their course through space little affected by the attraction of the central mass because of the great distance involved4 ,the portions nearer the point of impact receive orbits curved by this same attraction and the curvature becomes the sharper the nearer the axis of rotation4 ,one result of the mutual gravitation between the central mass and the particles in the outer sections of the nebula is also that the velocity in the spiral arms becomes smaller the farther the section in question is located from the centre1 just as comets in the solar system move slower the farther they are removed from the ,sun4 ,but in all portions outside the central region the attraction is too weak to give circular orbits to the gaseous matter4 ,all substance in these localities1 therefore1 departs ever more from the centre4 ,as the spiral arms stretch out into straight lines such matter finally leaves the central disk altogether4 ,it is possible that only the disk itself remains in the nebula computed by ,pease4 ,another astronomer on ,mount ,wilson1 ,a4 ,van ,maanen1 has investigated a nebula1 ,no4 #aja in ,messier's catalogue 7,fig4 #d74 ,this nebula lies nearly at a right angle to the line of vision which consequently almost coincides with the axis of rotation4 ,the motion of the different parts of this nebula has been calculated with the help of photographs taken in the years #ahii1 #aijh1 and #aiad1 whereby its changed position with reference to surrounding fixed stars has been recorded4 ,out of #hg points in the spirals only #i moved in the direction of the hands on a clock while the other #gh moved in the opposite sense4 ,the mean angular velocity is #j4jbb seconds of arc per year1 corresponding to #he1jjj years for one complete revolution at #e minutes' distance from the centre4 ,the absolute velocity #b minutes of arc from the centre is #a4e times as great as at #g4e minutes' distance4 ,fig4 #d is reproduced from ,van ,maanen's original4 ,it shows clearly the general regularity in the motion of the component parts as well as the numerous exceptions to the rule4 ,such exceptions may be caused by perturbations due to invading masses1 which impart their own motion to the entangling matter4 ,these foreign bodies have probably condensed surrounding vapours and this created the bright knots which stud the nebular spirals4 ,the upward motion amounts on the average to #j4jjg seconds per year4 ,while the points of condensation describe half a revolution around the centre they depart therefrom to about twice their original distance4 ,more than a million years is therefore likely to elapse before the outer portions of the nebula are so far removed from the nucleus that the spiral form of the nebula is no more apparent4 ,illustration3 ,fig4 #d4 ,internal motions in ,messier #aja4 ,the arrows indicate the direction and magnitude of the mean annual motions4 ,their scale 7#j0a7 is indicated on the plate4 ,the scale of the nebula is #amm #aj0e4 ,the comparison stars are enclosed in circles4 ,from ,proceedings of the ,national ,academy of ,sciences of ,u4 ,s4 ,a4 ,illustration3 ,fig4 #e4 ,spiral nebula ,no4 #ea in ,messier's ,catalogue2 situated in ,canes ,venatici1 and photographed ,february #g and #h1 #aiaj1 from ,mount ,wilson ,observatory in ,california4 ,scale3 #a millimeter #e sec4 arc4 ,lyran ,herkules ,ormbraren rnen ,sklden ,svanen ,rven ,pilen ,ormbraren ,skytten ,skorpionen ,sdra ,kronan ,kolsck ,syd-,korset ,skeppet ,argo ,klen ,skeppet ,argo ,styre ,segel ,n ,enhrningen ,enhrningen ,kusken ,cepheus ,perseus ,kassiopeja ,svanen ,it is clear that the ,milky ,way may have been formed through the collision of two immense nebulous gas-aggregations in the manner just described4 ,subsequently and by virtue of the magnitude of the ,galaxy great quantities of wandering cosmic matter and minor stellar bodies have been gathered in occasionally accompanied by larger clusterings such as the planetary nebul referred to4 ,how well justified we are in looking upon the ,milky ,way as a spiral nebula is apparent from the picture 7,fig4 #e7 reproducing a photograph of the familiar regular nebula in the ,dogs 7,canes ,venatici74 ,it shows a wealth of detail hitherto not surmised4 ,the feat was accomplished in the ,carnegie ,observatory on ,mount ,wilson in ,southern ,california with the help of optical resources vastly superior to all earlier means4 ,the ,milky ,way has previously been compared to this nebula1 but due to deficient enlargement their striking similarity has not been fully recognized until now4 ,assume the ,sun located in the point marked 8,s0 in ,fig4 #e and some distance above the plane of the picture1 then the nebula if viewed from this point would appear somewhat as the ,milky ,way appears to us4 ,in the middle we behold the substantial nucleus and on its left side a cleft between the two branches of the inner spiral4 ,farther to the left1 we see only the outer spiral1 first broadening toward the left where it approaches 8,s10 then narrowing only to spread again on account of the great clustering in the lower right part of the spiral4 ,the axis of the nebula corresponds to the densest parts of the ,galaxy in ,cygnus 7the ,swan71 the loop in the inner spiral again to the empty space between ,cepheus and ,cassiopeia1 the narrow part of the outer spiral branch resembles the constriction at ,algenib1 the following diffusion corresponds to the broad section in ,auriga 7,charioteer7 and ,monoceros 7,unicorn74 ,at the subsequent narrow place we see the outer nebula-clump corresponding in certain respects to the ,magellanic clouds on our firmament although these are farther removed1 and apparently not indigenous to the ,milky ,way4 ,there follows in the nebula a massive section in our system represented by the well known1 far less compact1 yet brightly luminous tract containing the ,southern ,cross4 ,here1 from the star ,alpha in ,centaurus--the nearest bright fixed star#c to our ,sun1 8only0 #d4e light years or about #be trillion#d miles distant--commences a bi-section of the spiral and strangely enough the nebula is similarly forked4 ,now the outer spiral stretching in a faint line upward from the 8clump0 begins to show as a weak band1 while the inner spiral stands forth powerfully above 8,s0 corresponding to the brilliant section of the ,galaxy in ,scutum 7,shield7 and ,aquila 7,eagle74 ,the partition in the nebula between these two branches is the counterpart of the #aaj long 8prong0 in the ,milky ,way between the constellations ,norma and ,lyra4 ,numerous faint bridges join the two branches in the nebula as well as in the ,galaxy1 according to ,wolf4 #c ,up to a short time ago ,alpha ,centauri was considered the fixed star nearest to the ,sun4 ,by comparing old photographs of the firmament with such of recent date the renowned astronomer ,barnard found that a very small fixed star--of the magnitude #aj4e and therefore far from visible to the naked eye--in the constellation ,ophiuchus 7,right ascension #ag h4 #eh m4 #dd s41 ,north declination #d #bg4d ,january #a1 #aiag7 possesses a very large proper motion4 ,it traverses in a year #aj4c seconds on the firmament4 ,the distance to this star1 which has the largest proper motion so far known1 was later determined to be #c4c light years or #c_/d of the distance from ,alpha ,centauri to our ,sun4 ,hence its velocity at right angle to the line of vision is computed to be #di km4 7#cb miles7 per second4 ,spectroscopic measurements show that it approaches us with a velocity of #ia km4 7#ef4e miles7 per second along the line of vision4 ,the combined velocity1 therefore1 is #ajc km4 7#fc miles7 per second1 an unusually high value4 ,the value of #c4c light years used in this calculation was determined by the ,french astronomer ,gonnessiat1 who found it by the study of old photographs from ,algeria4 ,he also calculated the parallax of this star to be #a second4 ,according to later measurements1 given in the ,harvard ,bulletins #faf and #fag1 its parallax is only #j4g seconds and consequently its distance #d4f light years and its speed perpendicularly to the line of vision #gj km4 7#dc4e miles7 per second4 ,campbell1 in the ,lick ,observatory1 had determined its radial velocity and found that it approaches the ,sun at the rate of #abh km4 7#gi miles7 per second4 ,its total velocity is1 according to these two last determinations1 #adf km4 7#ia miles7 per second4 ,it is by no means improbable that similar discoveries will be made in the future1 so that the ,sun will be found to have more stars in its 8immediate0 vicinity than previously assumed4 #d ,american and ,french numeration2 the ,swedish and ,english usage is billion4 ,the correspondence is indeed surprisingly good4 ,proportions are1 of course1 somewhat different--in particular is the central part of the ,galaxy not so predominating1 which fact has been troublesome to the adherents of the nebula theory4 ,probably it was originally denser but has become attenuated through star-formation1 explaining1 for instance1 the great gap between the constellations ,lyra and ,vulpecula4 ,to give a better idea of the structure of the ,milky ,way1 two photographs are here reproduced as taken by ,wolf1 the ,german astronomer in ,heidelberg1 who has done particularly meritorious work in this department4 ,one 7,fig4 #f7 shows a section of the ,galaxy in ,cygnus 7the ,swan7 with the star ,deneb in the centre and to the left the 8,northamerican-nebula0 so named from its shape4 ,above ,deneb is the dark 8hole0 in ,cygnus and below another chasm not quite so black4 ,left of the 8hole0 is the winding canal enclosing the so-called ,cocoon nebula4 7,see ,worlds in the ,making1 page #agb47 ,the following picture 7,fig4 #g7 contains1 in the upper left1 the bright star ,altair in ,aquila 7the ,eagle7 located close to the powerful arm of the ,galaxy in this constellation4 ,farther to the right is the fainter arm in ,ophiuchus 7the ,serpent-holder74 ,the lower half contains the most brilliant part of the ,milky ,way in the constellations ,scutum 7the ,shield7 and ,sagittarius 7the ,archer74 ,bright stars are infrequent but the fainter ones are innumerable3 8,they are crowded into dense clusters and between them the most delicate star dust is scattered40--8,we behold how the star-ribbon dissolves into detached tufts which intertwine into the strangest patterns4 ,these clouds of stars reach their greatest splendour in the lower part of the map40 ,illustration3 ,fig4 #f4 ,the ,milky ,way between constellations ,cassiopeia and ,swan from photo by ,m4 ,wolf of ,heidelberg4 ,a little to the left of the middle the beautiful nebula ,america appears4 ,illustration3 ,fig4 #g4 ,the ,milky ,way in constellations ,eagle 7upper half7 and ,archer 7lower half74 ,in the upper left the bright star ,altair appears4 ,photo from ,m4 ,wolf of ,heidelberg4 ,we also reproduce 7,fig4 #h7 from ,m4 ,wolf a photograph in larger scale from the region of ,gamma 7lower part of ,fig4 #g7 in the ,eagle with its 8trident-hole10 so called from its peculiar shape1 and in whose vicinity mists and star-clouds abound4 ,this picture is a more complicated counterpart of the flatter photograph by ,wolf of the 8,cocoon nebula40 ,it appears as if three or four stellar bodies here had stepped in from without1 swept away the stars in their way1 and left clean 8streets0 behind4 ,probably other 8empty0 spots in the neighbourhood have been formed in a similar manner4 ,another theory is that such dark places are caused by opaque mist-formations which shield the light of the stars behind from our sight4 ,illustration3 ,fig4 #h4 ,the trisected hole 7,trifid-hole7 in ,eagle4 ,photo from ,m4 ,wolf of ,heidelberg4 ,through these pictures we gain a conception of the manner in which the present stars in the ,milky ,way have clustered out of the original misty chaos4 ,we cannot avoid the idea of great exterior similarity between the lumps formed in curdling or souring milk and those which we observe in the ,milky ,way4 ,the renowned ,french scientist ,duclaux says in his micro-biology3 8,in milk1 commencing to sour1 but yet entirely liquid1 we observe under the microscope a precipitation of tiny particles4 ,to begin with they are seen with difficulty and are discovered only by slightly displacing the plane of vision4 ,later they develop into distinct grains1 characterized by ,brownian movements1 just like small particles of clay4444 ,still later the phenomenon appears as a steady molecular agglomeration4 ,the grains have the tendency of the clay particles to lump and precipitate40 ,the first condensation-nuclei in the mist-clouds are no doubt cosmic dust entering from without and perhaps also larger clusterings such as meteorites and comets4 ,at the existing low temperature1 surrounding gases condense into fluid state on the dust particles which by virtue of these moist shells are cemented into aggregations of such size that gravitation overcomes the repelling radiation pressure4 ,gravitation assisted by the retarding vapours further mass these aggregates together4 ,this process of coalescence is accompanied by heat production4 ,finally1 small stars are formed1 then groups of such stars1 while the spaces between1 now comparatively devoid of matter1 appear dark much as the whey between flocks of curd4 ,as yet1 the small stellar bodies are surrounded by quantities of dust and gas1 which1 however1 with continued condensation become ever more rarefied4 ,even yet the big stars in ,pleiades1 belonging to the helium group1 appear on the photographic plates interspaced with great patches of dust-clouds4 ,these are now1 however1 so unsubstantial that they offer little impediment to the procession of the mighty stars4 ,the condensation process may be greatly accelerated through the invasion of voluminous gas nebul similar to the ,cocoon nebula4 ,at last all gases in the new star condense1 that is to say the shell of tenuous vapours and dust contracts to such an insignificant thickness that it cannot be seen except possibly from the immediate vicinity4 ,small bodies ingathered through friction against the remnants of the original extended wrapping wander as planets around the new sun1 sweeping away the last traces of unattached matter4 ,the condensation on the new orb leaves a 8hole0 in the nebulosity which in this way is transformed into stars and their satellites which emerge from the mist and scatter on the firmament4 ,the ,milky ,way appears to be in a rather advanced stage of this evolution4 ,the 8infinitely small0 presents occasionally surprising likeness to the 8infinitely large40 ,in this manner we can form a conception of the growth of the wonderful structure which has brought forth the majority of the stellar bodies that we discern4 ,the spiral nebul visible at the ,galactic poles are similar formations but probably of far more modest dimensions4 ,they may compare to the ,milky ,way as the smaller planets to the ,sun4 ,according to recent investigations the spiral nebul seem also to possess an enormous velocity and they have probably invaded the ,milky ,way from without4 ,as previously stated1 an exceedingly remarkable conception of the ,milky ,way exists among the ,mexicans4 ,to them it is the ,matrix of all and gave birth to the stars1 the most important of which are the ,sun1 the ,moon1 and ,venus4 ,this idea evidently agrees very well with the results of investigations in the last few years4 ,finally1 a few words about the extent of the ,milky ,way4 ,so far we have not been able to measure it2 only rather uncertain approximations are possible4 ,wolf estimates the diameter1 that is the distance between the two spirals at the point where the ,sun now is1 to be about #aj1jjj times the distance from the ,sun to the nearest fixed star1 ,alpha in ,centaurus1 which distance on the other hand is about #aj1jjj times the distance from the ,sun to the remotest known planet1 ,neptune1 or #cjj1jjj times that from ,sun to ,earth4 ,expressed in the usual units1 we arrive at #dj1jjj light years or #djj1jjj trillion kilometres 7#bdj1jjj trillion miles74 ,lord ,kelvin makes another estimate of #fjjj light years1 that is seven times smaller4 ,the mean diameter of the nebula proper might be about five times larger1 in round figures one hundred thousand light years1 or one billion billion kilometres 7#fjj million billion miles74 ,like a monstrous octopus1 the ,milky ,way swims in the fathomless ether-sea4 ,its dimensions are about as many times larger than those of the earth as that globe is larger than an atom4 ,this has caused the gifted ,irish physicist ,fournier ,d',albe to consider the celestial globes as atoms1 out of which systems of the order of the ,milky ,way are constructed in the same manner as the earth and other stellar bodies are upbuilt with atoms1 invisible to us and yet measured with an incredible degree of accuracy4 ,fournier ,d',albe goes further still4 ,in poetic flight he does not hesitate to endow the ,milky ,way organism with life4 ,its evolution cannot be denied a certain similarity to the processes of life4 ,the great nebula owes its origin to the union of two individuals1 two nebulosities1 who met in their course through boundless space4 ,there floated the newborn extending its tentacles in the cool ether-waves and gained substance and strength through the smaller beings which the surging billows brought within its reach4 ,it has now attained the zenith of its evolution1 and is breaking up into molecules1 or solar systems1 which again are composed of stellar bodies1 or atoms within the molecule4 ,in violent exuberance of youth these rush through space in fulfilment of their individual life4 ,many will in due time undoubtedly become dust again and then serve to nourish a new youthful nebula4 ,others succumb to a freezing-death but will be restored to life in collision with a nebulosity or some other stellar body and give form to 8new stars0 or planetary clouds4 ,again and again shall the starry mists go through the cycle of existence and after a lifetime1 whose duration stands in proportion to their dimensions1 i4 e4 may be estimated to billions of billions of years1 give rise to new celestial beings4 ,thus shall it for ever continue in an eternal rhythm4 ,,chapter ,,iii ,,the ,,climatic ,,importance ,,of ,,water ,,vapour ,when ,aristotle1 for two thousand years our leading savant in cosmography1 about twenty-three centuries ago stated the foundation of his natural science1 he laid down as the important principles3 moisture and heat and their opposites2 because the four elements out of which everything was made1 were3 earth1 characterized by dryness and cold2 water1 which was moist and cold2 air1 which combined moisture with heat2 and lastly fire1 which stood for dryness and heat4 ,undoubtedly he was considering the requisites of life1 which may be designated as humidity and heat4 ,we have seemingly agreed that all life originates in the sea1 so that moisture can be considered the first requirement for its appearance on the earth4 ,as to heat1 life is destroyed by frost and favoured by increased warmth1 at least to a certain point1 about #ce to #dj ,c4 7#ie to #ajd ,fahrenheit71 which temperature is most propitious to the development of life1 while a further increase is detrimental1 so that already below the boiling point of water life suffers more harm than at temperatures below freezing4 ,in fact1 the geologists have found that the different epochs in earth's evolution are best characterized by their humidity or dryness4 ,to arrive at a clear conception in these matters we shall briefly survey our present knowledge of the importance for the evolution of life on earth that we should attach to the humid and to the dry periods or localities4 ,we are all familiar with the heavy1 moisture-laden warmth which meets us when we enter a hothouse4 ,it is particularly favourable to the growth of plants and to the prosperity of the lower animals4 ,to the higher animals and to man1 the humid heat is not so beneficial4 ,in the open such hothouse air exists only in the tropics4 ,particularly the ,congo region and the parts of ,brazil adjoining the ,amazon ,river are remarkable for their humid heat and for their fabulously luxuriant vegetation4 ,from our greatest living climatologist1 ,julius ,hann1 ,i have borrowed the following description of such a clime3 8,the changes of temperature between the coldest and the hottest month are very small in the ,congo1 from 4#e to #e ,c4 74#i to #i ,fahrenheit71 with an average of about #c4e ,c4 7#f4c ,f474 ,the difference between day and night reaches nearly thrice this value1 or #i4e ,c4 7#ag4a ,f474 ,the dry season becomes shorter the more we approach the equator and in ,equatorville and ,bangala it shrinks to nothing4 ,during the rainless months1 a dense humid fog settles morning and evening over the savannahs4 ,low hanging clouds of uniform thickness frequently hide the ,sun for weeks at a time4 ,it is during the rainy season alone that we see a clear sky between the showers4 ,this season opens and closes with magnificent thunderstorms coming from the east4 ,in ,luluaburg1 lightning occurs during not less than #ajf days in the year4 ,in the dry season the wind carries with it clouds of dust which falls to the ground4 ,the cloudiness is enormous in the ,congo basin1 so that there are veritably no months with a clear sky in this part of the world4 ,in ,vivi1 the number of overcast days averages #gd per cent41 fluctuating between #fc per cent4 in ,august and #hc per cent4 in ,november4 ,the humidity is very high1 varying in ,vivi from #gj to #gi per cent41 with a mean value of #ge per cent41 and in ,bolebo the mean itself reaches #gi per cent4 ,during the rainy season1 the heat is sometimes unbearably oppressive2 suffocating fumes rise from vegetable matter which rapidly decays in the excessive humidity4 ,the annual precipitation does not reach very startling figures2 it varies between #abj and #ahj cm4 7#dg to #ga inches74 ,in ,gabun1 close by1 the sky is almost continuously covered with clouds during the dry season4 8,corresponding regions in ,south ,america are in parts characterized by an even higher humidity4 ,in ,iquitos by the ,amazon ,river1 it reaches not less than #hc per cent4 of saturation4 ,the annual change of temperature is only about #e ,c4 7#i ,f472 in ,para 7#a4jh south latitude on the coast7 it shrinks to #a or #a4e ,c4 7#a4h to #b4g ,f474 ,in the course of twenty-four hours the variation is considerably larger4 ,the sky is remarkably clear between showers during the rainy season4 ,in the interior of ,guiana1 the rains continue from the end of ,april well into ,july or even into ,august4 ,abundant dew is common during the rainless part of the year1 thus maintaining the humidity4 ,sun and ,moon are rarely visible1 and gigantic lightning storms announce the arrival of the rainy period40 ,similar conditions apparently prevailed during the carboniferous period1 which was characterized by a luxuriant vegetation4 ,the mighty tree-trunks of that time fell into the water-covered marshes out of which they had grown and their decay was thereby prevented4 ,instead they turned into coal like the peat in the mosses of today4 ,this was for some time thought to indicate that the temperature was not particularly high--,frech estimated about #ab ,c4 7#ec4f ,f47 7#aiaj74 ,but since the discovery and subsequent description by ,keilhack 7#aiad7 of peat-beds on ,ceylon1 where the average yearly temperature is #bf ,c4 7#gh4h ,f471 a return is to be expected to the older conception1 which held that the vegetation during the carboniferous period is evidence of a very warm climate4 ,judging by the appearance of fossil plants1 the temperature should have been nearly the same all over the globe4 ,carthaus remarks that the air was stirred by only feeble winds because the trees of that age with their great dimensions but frail root-systems could not have withstood a fresh breeze4 ,the sky was hidden behind a continuous thick cover of clouds which only let a faint light sift through to the ground4 ,the motionless air was almost saturated with moisture4 ,the luxuriance of the vegetation1 transcending anything existing today1 indicates a favourable high percentage of carbonic acid in the air4 ,this combined with the humidity and the dense clouds caused the heat radiation from the ,sun to be almost entirely absorbed by the upper strata of the atmosphere in which thereby a strong circulation was maintained4 ,as a result1 the heat was nearly equalized between the poles and the equator and under the cloud cover an almost constant temperature reigned day and night1 summer and winter4 ,the damp air stood wellnigh still and was filled with dense fog at the smallest changes in temperature4 ,lack of light prevented the development of flowers1 and the thriving plants belonged mainly to the ferns and to the horsetails4 ,pine and fir trees were yet comparatively few4 ,the conditions in the swampy regions where plant life flourished were nearly identical with those in a hothouse if we were to draw a dense veil in front of the windows in walls and ceiling so that a continuous twilight would prevail4 ,in this uniform climate1 plant life developed enormously faster than animal life4 ,the dense clouds could store considerable quantities of heat in the equatorial belt through evaporation in their upper layers and the violent wind storms above the clouds would carry the aqueous vapours to colder regions where the heat would be liberated through new cloud formations4 ,currents in the oceans now largely attend to this heat transportation and give for instance to the coast of ,norway1 and indeed to the whole of ,western ,europe1 its remarkably mild1 and to life and civilization1 propitious climate1 but in the carboniferous age humid air currents fulfilled the same task4 ,they moved considerably faster and more evenly than the ocean currents1 were not checked or deflected by coasts or islands1 and could therefore produce the extraordinarily uniform temperature and the marine climate all over the globe4 ,such a heat distribution takes place also in our days at a height of about #aj1jjj m4 7#f4b miles7 in the so-called 8stratosphere10 but the temperature here is very low1 about -#fj ,c4 7-#gf ,f471 so that the vapour suspended is hardly worth mentioning1 and cannot give rise to cloud formations4 ,the quantities of heat carried in these higher strata of the atmosphere are too insignificant to influence the masses of air below1 whose temperature1 therefore1 is almost entirely governed by that of the sun-heated surface of the earth1 except where the ocean currents equalize matters1 as for instance in the almost wholly water-covered latitudes south of the #cjth parallel on the ,southern ,hemisphere4 ,even during the carboniferous period at its height1 there existed1 of course1 a temperature difference between pole and equator1 but it was very small1 some #aj ,c4 7#ah ,f47 perhaps4 ,undoubtedly1 the formation of coal beds was mainly confined to those regions where the climate was most uniform all the year around4 ,the opposite extremity1 the dry desert climate1 is far more pronounced in the present time4 ,this condition is well known in all continents except ,europe1 where we hardly can claim a desert but instead have steppes1 with a vegetation abundant after the spring rains but fast disappearing with the arrival of the burning summer heat4 ,a particular type of plant life has adapted itself to this periodic change from rain to drought1 from bitter cold during the winter to parching sun during the summer4 ,perennial plants1 and particularly trees1 can rarely endure the rigors of such climatic upheavals4 ,animal life on the other hand has proved fairly adaptable and displays considerable wealth4 ,this steppe climate is only an intermediate stage towards the desert climate proper1 which is hostile to all life4 ,its temperature is subject to enormous changes in the course of the day and the year4 ,the annual variation is less pronounced near the equator and the daily variation less on the approach to the poles1 on account of the small changes in the sun's radiation during corresponding periods4 ,the difference between day and night in ,sahara is frequently #cj to #dj ,c4 7#ej to #gj ,f474 ,the lowest temperature observed by ,foureau-,lamy1 #ahih-ahii1 was -#bj ,c4 7-#d ,f47 or nearly the same as on the ,scandinavian coasts4 ,the highest amounted to #dh ,c4 7#aah4d ,f47 or a total variation of nearly #gj ,c4 7#abf ,f474 ,in ,upper ,egypt 7#ba4i ,n4 ,lat47 the mean temperature changed from #af4c ,c4 7#fa4c ,f47 in ,january to #cd4a ,c4 7#ic4b ,f47 in ,july1 and nearer the equator in ,central ,africa 7#h4a ,n4 ,lat41 #bc4f ,e4 ,long47 the difference amounted to only #f4i ,c4 7#dd4f ,f471 #bb4g ,c4 7#gb4e ,f47 in ,december1 #bi4f ,c4 7#he4a ,f47 in ,april1 while in ,kiachta 7#ej4d ,n4 ,lat41 #ajf4e ,e4 ,long47 in ,siberia1 the yearly change reaches #de ,c4 7#ha ,f471 -#bf4f ,c4 7-#ae4g ,f47 in ,january1 #ai4a ,c4 7#ff4b ,f47 in ,july4 ,the average daily variation at continental stations is about #ab ,c4 7#ba4f ,f474 ,all this refers to the temperature of the air1 while the surface temperature in the course of twenty-four hours may change #ej ,c4 7#ij ,f47 and in the desert even more4 ,frost occurs in the ,sahara as late as ,may when the maximum temperature may reach #ej ,c4 7#abb ,f474 ,while in ,scandinavia the diurnal difference between highest and lowest temperature averages only #f to #g ,c4 7#aa to #ac ,f471 a maximum in ,july of #aj4d ,c4 7#ah4g ,f47 and a minimum in ,november of #d ,c4 7#g4b ,f471 ,hedin on his journey in ,tibet1 #ahii-aijb1 observed a daily variation of #ai ,c4 7#cd4b ,f47 and no appreciable difference with change in altitude4 ,the result of such a violent temperature change in the course of a day is a breaking up of the rocks which subsequently and gradually are ground to fine dust by unobstructed winds wherever vegetation does not bind the soil4 ,in this manner the sand deserts are formed4 ,the arid wastes of ,asia have lately been vividly described by ,sven ,hedin4 ,the mountains eroded by the sandstorms resemble dilapidated ruins1 standing as monuments of an ancient highland4 ,the sand in ,east ,turkestan is reduced to such a fine powder that it can float in the air for several days after a storm1 revealing itself in gorgeous sunsets4 ,winds sweep the sand into long dunes1 which shift in the direction of the blast4 ,it is ferruginous and therefore red or if powderized reddish-yellow4 ,when moistened it assumes a brown to black shade4 ,after rain1 the water descends toward the valley1 carrying with it the sand in the form of silt4 ,this1 through evaporation1 is transformed into a plastic black dough1 slides like a glacier slowly down the hillsides1 and finally comes to rest in some broad hollow which it gradually fills4 ,such a silt aggregation is called in ,persia a 8,kevir40 ,its surface dries1 but the interior remains moist4 ,as evaporation continues it becomes richer in salt so that white crusts of this substance are formed during dry periods4 ,in other districts1 as in the basin of the ,tarim ,river1 the water occasionally appears in the lowest parts1 the so-called 8,bayirs0 7see ,fig4 #i71 formations similar to the ,kevirs1 or in salt lakes between the sand dunes4 ,sand carried by the winds quickly fills these lakes so that they too move in the direction of prevailing winds4 ,they lie with their longest dimensions parallel to each other and at right angle to the course of the ,tarim ,river4 ,the sketch map taken from ,hedin's work shows the ,bayirs strung out in line with the lakes somewhat like panels in a tapestry pattern4 ,this reticulation of the landscape is the result of the dune formations4 ,the main dunes with steep western slopes run in the direction ,n4,n4,e4-,s4,s4,w4 ,they stand at right angle to the prevailing winds4 ,nearly perpendicular to their crest lines dunes of smaller height are thrown up by winds in another common direction but less frequent than those which raised the fundamental dunes4 ,this system brings to mind the cloud formations called mackerel sky1 clouds rippled in two directions frequently almost at right angle to each other4 ,they owe their peculiarity to two series of wave motions propelled by winds from two different directions in the upper strata of the atmosphere4 ,the cloud patches correspond to the wavecrests on a surging sea4 ,the map of the ,bayirs suggests a chessboard with squares somewhat elongated and irregular4 ,illustration3 ,fig4 #i4 ,tarim river with adjacent lakes and ,bayirs1 drawn by ,sven ,hedin4 7solid arrow7 ,predominating direction of winds4 7dashed arrow7 ,direction in which the river is shifting4 7hollow box7 ,vegetation4 7dotted box7 ,sand4 7horizontal lines in box7 ,lakes4 7vertical lines in box7 ,bayirs4 ,we may now return to a closer study of the largest of these formations1 the great ,kevir in ,persia4 ,this mud-lake1 with a dry surface1 measures #ejj km4 7#caj miles7 in length and #bjj km4 7#abd miles7 in width over its largest dimensions4 ,hedin estimates its area at #ee1jjj sq4 km4 7#ba1adb sq4 miles7 or the same as that of the great ,lake ,michigan on the boundary between the ,united ,states and ,canada4 ,due to the continuous growth of the salt proportion through the inflow of ,kevirs and through superficial evaporation a salt crust of varying thickness is formed near the surface of the lake4 ,hedin caused a hole to be cut with an iron bar4 ,he first encountered a #aj cm4 7#c4i in47 deep covering of clayey paste1 and then the salt crust about #g cm4 7#b4h in47 thick resting on a semi-dry layer of clay with a depth of #ae cm4 7#e4i in474 ,farther below1 softer strata of clay followed1 becoming more watery the deeper he went4 ,the iron bar carelessly wielded would have disappeared in the mire4 ,another investigator1 ,buhse1 examined a piece of the crust1 which when dry is fairly solid and of a yellowish-grey colour4 ,one half consisted of sand 7probably quartz-sand71 one sixth of limestone1 #f4a per cent4 oxide of iron 7causing the yellow colour71 #e4c per cent4 common salt1 #b4e per cent4 sulphate of sodium1 and #b4a per cent4 clay4 ,rain converts this surface layer into a plastic mass1 which persistently sticks to the clothes of the traveller or to the bodies of the camels if they should slip and fall into the mud4 ,not the slightest trace of vegetation or of any life exists4 ,on the shore of the mud-lake small flat elevations and depressions may be found2 otherwise1 the surface is as level as that of an ordinary lake4 ,the ,kevir battles with the drifting sand as does the water in ,east ,turkestan4 ,the sand appears to gain in the contest4 ,after storms1 vast portions of the ,kevir are covered with yellow desert sand4 8,if the climatic change in ,persia continues in the present direction10 says ,hedin1 who1 however1 is dealing with large spans of time inasmuch as in his opinion no appreciable alterations have taken place since the invasions of ,alexander the ,great1 8then it may be taken for granted that the slough of the ,kevir will lose in moisture and afflux of water and in time will become more solid and that the drift sand with greater ease will gain foothold and territory4 ,the final outcome of the physico-geographical transformation now in progress will no doubt be to convert the entire ,kevir into a sand desert of the kind predominating in ,east ,turkestan4 ,and conversely we may infer that ,east ,turkestan1 once a part of the central ,asiatic ,mediterranean sea1 in the course of time was filled with the finely divided products of disintegration1 such as we now find in the ,kevir1 and further that its expanse of watery mud and clay finally dried and hardened to such an extent that it could support the load of the encroaching sand4 ,that the extension of the sand formerly was smaller1 is also borne out by the archological discoveries in ,east ,turkestan which several travellers besides myself have made4 ,the hardpan laid bare in the #8,bayirs' of the ,cherchen desert strongly reminds of the ,kevir-ground4 ,in both cases the same dark1 fine powder forming a nearly plane surface4 ,in both cases this material when mixed with water is transformed into a slough in which one hopelessly sinks1 but in ,east ,turkestan the water has receded to a greater depth and as rains are extremely rare travel all over the smooth #8,bayir'-ground may be undertaken with impunity40 ,these formations are of the greatest interest because they picture the changes taking place on a slowly desiccating planet4 ,in #aheh the ,geographical ,society in ,petrograd despatched an expedition under the command of ,khanikoff to visit these regions4 ,from ,hedin's work1 ,overland to ,india1 from which the preceding quotation is taken1 we borrow the following vivid description by ,khanikoff3 8,at last1 in the morning of ,april fourth1 and during the most oppressive heat1 we reached ,bala-haus4 ,at this place remnants of a ruined reservoir1 long since bereft of its water1 could be seen4 ,the desert had here assumed the perfect character of the #8the accursed land1' which name it bears among the natives4 ,not the smallest tuft of grass1 not a sign of animal life gladdened the eye1 not a sound interrupted the deathlike1 awful silence but that of the marching caravan4 8,because of the slow procession of the camels and the delay suffered when we lost our way1 we only covered #be km4 7#ae4e miles7 in the night stage4 ,after four hours' rest we resumed our march and directed our steps toward the hills1 called ,kellehper and situated #bj km4 7#ab4e miles7 from ,bala-haus2 they were plainly visible but positively seemed to take flight on our approach4 ,i was somewhat ahead of the caravan and sat down at the foot of this sand-elevation2 and never can ,i describe the feeling of weariness and of depression that ,i was unable to ward off as ,i looked into the ghastly solitude that engulfed me4 ,scattered clouds intercepted the rays of the sun1 but the air was hot and heavy2 the diffused light lent a monotonous and disconsolating hue to the greyish1 burning surface of the desert2 hardly a single variation of colour gave relief to the immense expanses that the vision embraced4 ,the absolute immobility of every point in this mournful landscape1 combined with the complete absence of any sound1 produced an overwhelming depression of the spirit2 one felt as set upon a place that had been struck inanimate for ever1 a place to which organic life would never return safe through some terrible catastrophe of nature4 ,one witnessed the beginning1 so to speak1 of the death-agony of our planet40 ,if a drying out has taken place in these regions1--which seems probable from ,hedin's observation that the water in a ,tibet lake1 ,lakker-tso1 formerly reached a #acc m4 7#dce ft47 higher level than at present1--such a process is nevertheless not so obvious here as in the salt inland lakes1 for instance the ,great ,salt ,lake in ,utah1 the ,dead ,sea1 and the ,caspian ,sea1 where the saltness has greatly increased due to evaporation4 ,concerning the ,great ,salt ,lake we know that even at a comparatively late time it had a much wider extension than now4 ,its water contains #bb per cent4 common salt besides other compounds4 ,the ,dead ,sea holds #be per cent4 salt4 ,a very variable percentage is to be found in the ,caspian ,sea4 ,near the mouth of the ,volga it is of course low1 only #j4ae1 and increases southward to #a4cb at the peninsula ,apsheron and to #e4fc in the bay of ,kaidak4 ,in the gulf of ,karaboghaz on the ,asiatic side it reaches #bh4e per cent4 ,it has been computed that this gulf receives annually from the inrushing waters of the ,caspian ,sea #cej1jjj tons of salt which is partly deposited on its shores and bottom4 ,this desiccation1 however1 is a mere trifle when contrasted with the process by which the mighty salt deposits in ,germany were formed4 ,it took place1 we believe1 in a shallow bay extending southward from the ,arctic ,sea4 ,as the salts1 first gypsum1 then common salt1 and lastly more soluble potassium and magnesium compounds1 crystallized by degrees new water masses entered from the sea4 ,at the same time1 the bottom of the gulf slowly receded1 giving room for fresh evaporating floods4 ,the salt layers deposited in this manner sometimes reach a depth of more than #ajjj m4 7about one half a mile74 ,we can thus gain a conception of the immense quantities of water evaporated and the enormous time required therefor4 ,the deposits would long ago have been carried away from their original place were it not for the fact that they finally were covered with a layer of slime nearly impervious to water4 ,the most soluble salts1 such as chloride of magnesium1 have nevertheless been extracted to a great extent4 ,the extremes of aridity or humidity have of course not occurred during the brief time known to history4 ,of a special interest is the question in what direction the climate at present is tending4 ,in this connection1 ,huntington has aroused great attention by propounding the theory that the earth is now in a period of rapid desiccation4 ,judging by the testimony of geology1 it seems beyond doubt that an age of humidity prevailed simultaneously with the ice-period in northern ,europe1 over several parts of the globe1 in fact everywhere as far as we know except in ,australia4 ,this is clearly borne out by the higher levels of the lakes and their consequent greater extension in earlier days4 ,so far as ,tibet and ,central ,asia are concerned we have already mentioned this fact4 ,but in ,america and ,africa the humid period was even more patent4 ,the ,great ,salt ,lake has covered an area many times greater than at present as testify the picturesque terraces in its surroundings 7compare ,fig4 #aj74 ,according to the researches by ,passage1 this period was also strongly pronounced in ,africa4 ,a large fresh-water body occupied the ,congo basin1 the ,tsad lake had a far greater expansion than now1 and mighty rivers traversed ,sahara4 ,illustration3 ,fig4 #aj4 ,extension of the great ,lake ,bonneville in ,utah1 of which the ,great ,salt ,lake is a remnant4 ,it is often assumed that the climate of ,africa has been more humid even in historic times4 ,the geographer ,leo ,berg in ,petrograd1 however1 is emphatically opposed to this theory4 ,he points out that the writers of antiquity1 ,diodoros1 ,polybios1 and ,pausanias1 have given descriptions of the rivers on the ,north ,african coast which nearly agree with conditions today4 ,the location of two ancient cities on the shores of ,lake ,chott-el-,djerid in ,tunis 7,lacus ,tritonis of old71 which lake1 it is claimed1 reached a level very much higher than now #ejj years ,b4,c41 plainly demonstrates that the shore-line then ran very close to its present position4 ,students of ancient ,egypt are unable to find evidence of any distinct difference in the climate of that country from the earliest times to our days4 ,it is true that marshes in the ,nile delta have changed into splendid meadows--but this is the work of man4 ,the humid period must have ended long before history commenced4 ,a few of the old writers1 such as ,herodotos1 ,aristophanes1 and ,philo1 assert that rain never falls in ,egypt1 but this must be classed as an exaggeration when contrasted with references to rain1 snow1 and hail in this section made by other ancient authors1 for instance ,plutarch1 ,pliny1 and lianus4 ,at any rate it seems as if precipitation was as rare an occurrence in the land of the ,pharaohs as in the land of the ,nile of today4 ,against the statement by ,huntington that the climate of ,palestine has become very much more torrid during historic times1 stands the assertion by ,hilderscheid1 who has made a thorough study of these questions1 that no reason whatever exists for such a conclusion4 ,of greatest interest to us in this connection are perhaps ,italy and ,greece4 ,huntington believes that the river ,alpheios1 which flooded ,olympia and covered it with a #d m4 to #e m4 7#d or #e yards7 thick sediment1 carried a far greater volume of water formerly than today4 ,this flood1 however1 was caused by an earthquake accompanied by a fall of rocks whereby the river was dammed4 ,there is no necessity for assuming a greater abundance of the waterflow4 ,according to ,strabo1 the streams ,kefissos and ,ilissos1 between which ,athens is situated1 dried out during the summer then as they do now4 ,if we are to believe ,pausanias1 the brooks which traversed the ,argive plain behaved similarly1 and so they behave today4 ,from all we can judge1 the climate of ,greece has not changed perceptibly since the days of ,homer4 ,in regard to ,sicily1 it is stated that several of its rivers were navigable in the ,middle ,age1 while such is not the case now4 ,but this is explained by the devastation of the forests which formerly equalized the flow of these rivers1 and perhaps also by the size of the vessels of that time4 ,cultivation in these regions has sharply declined since antiquity4 ,as a consequence1 the loose soil1 which formerly was planted1 has been washed away and the dams and retaining walls1 built to prevent a too rapid drain of the water1 have disappeared4 ,thus the country has grown increasingly arid4 ,large cities1 as ,palmyra1 existed in desert regions where lack of water now prevents habitation4 ,but water was brought to the metropolitan cities of old through long magnificent aqueducts1 the ruins of which partly remain today4 ,we have all reasons to believe that the marked decrease in cultivation and population1 laid to changes in conditions of humidity1 depended altogether on man's interference with nature4 ,on certain rocks in ,morocco1 carvings have been found portraying in a simple way large mammals such as elephants1 rhinoceroses1 and giraffes1 which do not exist in these regions now because of lack of nourishment4 ,but these rough works of art1 resembling those of the bushmen of today1 date from prehistoric time1 the so-called paleolithic era1 when the climate admittedly was more humid in these regions than it is now4 ,similar conditions obtain1 according to ,hedin1 in ,central ,asia and in ,persia4 ,the climate there has without doubt been more humid but not in historic times4 ,the march of ,alexander toward ,india took place under as adverse conditions as now are found in these regions 7,baluchistan74 ,their cities1 now in ruins1 received their water supply through conduits from rivers some of which were then adjacent to the cities1 although they later have changed their course as pointed out by ,leo ,berg4 ,in ,western and ,central ,europe numerous marshes and morasses have indeed been drained and rendered available for cultivation1 but this does not prove that the climate is become more dry4 ,on the contrary all observations1 for instance those made by ,tycho ,brahe on the island ,hven1 indicate that the difference between summer and winter temperature has decreased during historic time2 that is the climate is become less continental1 or more humid1 than formerly4 ,furthermore1 many circumstances1 such as the occurrence of hazel and of water chestnut in far more northerly latitudes and the higher altitude of the timber line in earlier time1 prove that the summer in prehistoric ages was warmer than now4 ,simultaneously it was dryer4 ,a study of the lacustrine pile dwellings in ,switzerland shows that the levels of the lakes then were not higher than now but very nearly the same1 which demonstrates that the precipitation has not changed perceptibly in ,switzerland since these buildings were made2 the period in question occurred1 we believe1 about #gjjj years ago4 ,while great climatic changes have taken place since man's first appearance on earth1 presumably before the end of the ice period1 historic time is too short to record any distinct modifications4 ,local ones may be in evidence such as ,west ,europe's transition to a less continental climate4 ,a variation of this nature has been found not longer back than since thermometrical observations commenced4 ,thus the winters in ,berlin during the period #agdf-ahdg were colder and the summers warmer than during #ahdh-aijg4 ,the difference for ,january amounted to -#a4e ,c4 7-#b4g ,f47 and for ,may to #j4f ,c4 7#a4jh ,f474 ,the tabulation below1 quoted from ,ekholm1 shows the mean temperature in ,stockholm1 ,lund1 ,london1 and ,paris1 during winter 7,december-,february71 spring 7,march-,may71 summer 7,june-,august71 and autumn 7,september-,november7 and for the following periods3 ---------------------------------------- ---- ,stockholm ,lund ------------------------------------- #agii- #ahdi- #agec- #agii- #ahdh #ahih #agih #ahih ---------------------------------------- -- ,winter #be4e ,f4#bf4h ,f4#cj4b ,f4#cj4i ,f4 -#c4f ,c4 -#b4i ,c4 -#a4j ,c4-#j4f ,c4 ---------------------------------------- -- ,spring #cg4i ,f4 #cg4i ,f4 #da4b ,f4#da4e ,f4 #c4c ,c4 #c4c ,c4 #e4a ,c4 #e4c ,c4 ---------------------------------------- -- ,summer #fj ,f4 #fj ,f4 #fa ,f4#fj4b ,f4 #ae4f ,c4 #ae4f ,c4 #af4a ,c4#ae4g ,c4 ---------------------------------------- -- ,autumn #dc4i ,f4 #dc4e ,f4 #de4i ,f4#de4i ,f4 #f4f ,c4 #f4d ,c4 #g4g ,c4 #g4g ,c4 ---------------------------------------- -- ,year #da4i ,f4 #db4a ,f4 #dd4f ,f4#dd4f ,f4 #e4e ,c4 #e4f ,c4 #g4j ,c4 #g4j ,c4 ---------------------------------------- -- ---------------------------------------- - ,london ,paris ---------------------------------- #agii- #ahdi- #ahjf- #ahdi- #ahdh #ahih #ahdh #ahih --------------------------------------- ,winter #ch4e ,f4#ci4b ,f4#cg4i ,f4#cg4i ,f4 #c4f ,c4 #d4j ,c4 #c4c ,c4 #c4c ,c4 --------------------------------------- ,spring #dh4b ,f4 #dh ,f4#ej4e ,f4#ej4c ,f4 #i4j ,c4 #h4i ,c4#aj4c ,c4#aj4b ,c4 --------------------------------------- ,summer #fa4i ,f4#fb4b ,f4#fd4f ,f4#fd4h ,f4 #af4f ,c4#af4h ,c4#ah4a ,c4#ah4b ,c4 --------------------------------------- ,autumn #ej4g ,f4#ej4e ,f4#ed4b ,f4#ea4h ,f4 #aj4d ,c4#aj4c ,c4#aa4c ,c4#aa4j ,c4 --------------------------------------- ,year #i4h ,f4 #ej ,f4#ea4c ,f4#ea4c ,f4 #i4i ,c4#aj4j ,c4#aj4g ,c4#aj4g ,c4 --------------------------------------- ,the difference is not great4 ,for ,stockholm the winter has grown warmer1 the autumn colder1 for ,london the winter warmer and so slightly also the summer1 but spring and autumn a trifle colder1 and for ,paris the summer a little warmer while the autumn is considerably colder4 ,lund shows the least variation4 ,the winter has grown #j4d ,c4 7#j4gb ,f47 warmer and the summer colder by the same amount4 ,the annual mean remains nearly constant1 only slightly increased1 but the climate is become more marine4 7,this is hardly apparent from the figures cited as far as ,paris is concerned47 ,from ,tycho ,brahe's observations of the number of days when snow or rain fell in the place where his observatory was situated on the island ,hven in resund not far from ,copenhagen1 ,ekholm has calculated that the temperature there during the time #aehb-aeig was #a4d ,c4 7#b4e ,f47 lower in ,february and #a ,c4 7#a4h ,f47 lower in ,march than in later years 7#ahha-ahif74 ,on the other hand the first autumn frost occurred at the same time as now and the same was the case with the last frost in spring1 so that the temperatures on these dates in autumn and spring were nearly identical at the end of the sixteenth century and now4 ,ekholm drew the conclusion that the climate is become more marine4 ,hildebrandson makes the objection that ,tycho ,brahe's observations were confined to an abnormally cold period judging by the tables ,speerschneider has prepared showing the ice formation in ,danish navigable waters4 ,nine out of the sixteen years in which ,tycho ,brahe gathered his data were notable for abnormally cold winters1 while only nineteen out of the hundred years composing the sixteenth century were characterized by equally severe winters4 ,thus1 the conclusion is not warranted that the winters of the sixteenth century as a whole averaged colder than those of the nineteenth4 ,later investigations 7in #aiag7 in regard to the dates when the ice would break up in ,lake ,mlar at ,vesters1 in ,neva ,river at ,petrograd1 and in ,dwina ,river at ,riga1 have led ,ekholm to believe that he has found a periodicity in winter temperatures of not less than #bab years1 a conclusion which would agree with ,speerschneider's statistics4 ,if so1 we are at present living in a period remarkable for its mild winters while a series of extremely severe winter seasons occurred at the time of ,tycho ,brahe4 ,this law would also have a bearing on the preceding table of temperatures in ,stockholm1 ,lund1 ,london1 and ,paris as a succession of severe winters came around in the beginning of the nineteenth century while the reverse is true towards its end4 ,on the whole climatic variations during historic time have been insignificant1 if present at all1 provided we extend our comparisons over two or more centuries4 ,such is also the opinion of ,hildebrandson4 ,the idea of a slow deterioration of the climate due to increasing desiccation is of old lineage and is most likely related to the venerable conception of a bygone golden age4 ,aristotle even at that early date believed that a gradual arefaction of the ,earth took place4 ,in recent times this faith has been particularly fostered by ,huntington in a number of treatises where he endeavours to prove that ,asia1 represented for instance by ,palestine1 ,syria1 and ,persia1 and further ,africa and ,north ,america are subject to a rapid exsiccation clearly traceable through historic time4 ,the contrary1 however1 is true about ,western ,europe4 ,it was often said that ,southern ,russia in recent times suffered a slow arefaction manifesting itself in the formation of steppes4 ,this led to careful investigations showing the assertion to be erroneous and culminating in the work of ,leo ,berg4 ,rather1 a slight shifting in the opposite direction is detectable as the forest region has expanded at the expense of the steppes in conformity with the development toward the end of prehistoric time4 ,the renowned ,american astronomer1 the late ,dr4 ,lowell1 embraced the idea of increasing aridity which he observed himself in ,arizona where his observatory is located4 ,the drying out of ,arizona undoubtedly took place in long bygone prehistoric time4 ,the disappearance of a high culture in ,syria and ,mesopotamia was the result of hostile devastation of their waterworks2 a compensation is now offered in the reclamation of the deserts along the ,nile1 in ,california and ,arizona1 and in numerous other places4 ,,chapter ,,iv ,,atmosphere ,,and ,,physics ,,of ,,the ,,stellar ,,bodies ,in a certain sense1 we are justified in speaking of an atmosphere of suns and stars4 ,these bodies consist mainly of a comparatively dense mass surrounded by a layer of very attenuated gas4 ,the density of our ,sun is about #a4d times that of water4 ,in other stars it is considerably lower1 in some cases only a few hundredths of the density of water4 ,this applies particularly to those stars of variable magnitude1 the ,cepheid type1 named after their longest and best known representative1 the mysterious star ,delta in the constellation ,cepheus1 and in general to young stars4 ,in any case the stars are gaseous throughout on account of their high temperature4 ,an exception must be made for the clouds of matter precipitated by easily condensed vapours1 such as gaseous carbon1 which clouds float in the outer strata1 and are responsible for the bright astral light4 ,the stars just mentioned belong to the comparatively young stellar bodies1 while the ,sun in common with other yellow stars is considerably older4 ,correlated with their age is undoubtedly the greater mean density of the yellow stars4 ,around many of the young stars1 for instance around the brilliant ,altair1 the principal member of the constellation ,aquila1 a gas shell of great expansion has been observed1 usually consisting of hydrogen but frequently also of helium4 ,these extensive gas appendages may be considered as a kind of atmosphere surrounding the stars in question4 ,their density is no doubt exceedingly small4 ,our own central orb1 the ,sun1 is also endowed with rarefied gases outside of the luminous clouds4 ,by their absorption of light they cause the dark lines in the ,sun's spectrum1 after their discoverer named ,fraunhofer lines4 ,the greatest height from the surface of the ,sun is reached by hydrogen1 mixed with a small quantity of helium and with a gas1 unknown on ,earth1 which we call coronium because it has been observed in the ,sun's corona4 ,these gases may be looked upon as the atmosphere of the ,sun4 ,similar conditions obtain no doubt on the major planets1 which possess a density not essentially different from that of the ,sun4 ,they have1 moreover1 practically the same period of revolution around their own axis1 ,jupiter #i4i hours1 ,saturn #aj4c1 and ,uranus 7probably7 #aj4h hours4 ,judging by their density1 they are1 in all probability1 like the ,sun1 gaseous throughout except for the heavy cloud formations which appear to constitute the outer limit of these stellar bodies4 ,their interior1 like that of the ,sun1 may contain comparatively sluggish gas-masses1 as certain peculiar patches appear on their exterior1 similar to the sunspots and persisting for long intervals1 sometimes over a year4 ,the best known example of the kind is the so-called red spot on ,jupiter1 which has remained since #ahgh1 although it is not so pronounced now as during its early days 7see ,fig4 #aa74 ,characteristic for these planets are certain bands of a marked delineation and running parallel with the equator 7see ,figs4 #aa and #ab74 ,they are caused by the rapid peripheral motion of these planets1 with ,jupiter #bh and with ,saturn #bd times that of the ,earth4 ,illustration3 ,fig4 #aa4 ,the planet ,jupiter in #aiji in ,mercator's projection by ,f4 le ,coultre of ,geneva4 ,the 8red spot0 over which the clouds are dispersed1 is found at #cee ,long4 and #bj ,s4 ,lat4 in the outcurving of the dark band4 ,south direction is upward1 as on all pictures obtained with astronomical tubes4 ,which gases should we expect to find in the atmosphere of these planets8 ,according to the ,kant-,laplace hypothesis1 a theory generally credited with a sound kernel1 the planets were segregated from the ,sun's substance at a time when the latter was expanded so as to include the orbits of these planets and beyond4 ,naturally1 therefore1 their atmospheres would originally be composed of the very gases that formed the outmost part of the ,sun's atmosphere1 notably hydrogen4 ,slipher1 who has photographed the spectra here reproduced of the outer planets1 believes that certain strong absorption bands in the spectra of ,neptune and ,uranus correspond to the distinctive ,f and ,c lines of hydrogen1 using ,fraunhofer's denotation 7see ,fig4 #ac74 ,but because the bands in question1 as shown on the figure1 are very broad it is difficult to identify them with certainty4 ,also other gases of unknown origin enter into the vapour envelopes outside of the clouds and cause1 as apparent from their spectra1 a strong absorption of the sunlight reflected from the clouds below4 ,the absorption increases with the planet's distance from the ,sun2 thus1 it is most pronounced on ,neptune and least on ,jupiter4 ,illustration3 ,fig4 #ab4 ,the appearance of ,saturn ,september #cj1 #aiji1 according to ,f4 le ,coultre of ,geneva4 ,at any rate1 the gas appendages of the heavenly bodies just considered differ in one essential respect from the atmospheres of the inner planets3 ,mars1 ,earth1 ,venus1 and ,mercury4 ,on the ,sun and on the outer planets the atmosphere gradually merges into the interior gas-masses so that no distinct boundary can be found between the rarer and the denser layers4 ,widely different conditions obtain on the ,earth4 ,here the range of air is sharply defined below by the ,earth's solid crust or by the oceans4 ,in such case alone may we speak of an atmosphere proper1 of the kind that enters into our commonplace conceptions4 ,similar are the conditions on all stellar bodies with a solid or a liquid surface4 ,illustration3 ,fig4 #ac4 ,spectra of the major planets1 compared with that of the moon4 ,the latter corresponds to the spectrum of sunlight reflected from a planet which lacks a light-absorbing atmosphere4 ,photos by ,v4 ,m4 ,slipher of the ,lowell ,observatory4 ,but it is not certain in every case that all such planets possess an atmosphere4 ,observations of the ,moon when passing some star show that the air envelope1 if present1 is unable to deflect the light beam from the star1 or in other words it has no perceptible power of refraction4 ,from this we also infer that its density is very small1 corresponding at most to one or two mm4 74#jd to 4#jh inches7 barometric pressure4 ,but we have good reasons to believe that the ,moon has been detached from the ,earth1 carrying away parts of its lightest substance1 which theory is supported by the fact that the ,moon's mean density 7#c4c7 is only six-tenths of the ,earth's 7which again is #e4ec times that of water71 and we might therefore have expected that the ,moon in parting should have shared in the very lightest constituents of the ,earth1 namely its air-covering4 ,such was unquestionably the actual procedure1 but in the course of time the ,moon has lost its originally no doubt considerable atmosphere4 ,the reason is that the molecules in a gas are in a continuous rapid motion1 which is the swifter the lighter the gas and the higher its temperature4 ,in hydrogen1 the lightest gas known1 the velocity amounts to #a4hd km4 7#a4ae miles7 per second at #j ,c4 7#cb ,f474 ,the parts of the ,moon exposed to the strongest sunlight are heated to about #aej ,c4 7#cjj ,f474 ,at that temperature1 the average velocity of hydrogen molecules is #b4bi km4 7#a4dc miles7 per second4 ,but a body departing from the surface of the ,moon at a rate of #b km4 7#a4bd miles7 per second1 or more1 cannot be retained by the attraction of that globe and therefore never retraces its path but speeds away for ever4 ,in the same manner a bullet ejected from a cannon with an initial velocity of #aa4b km4 7#g miles7--a velocity not even approached by present artillery--would fly away from ,earth barring the resistance of the air4 ,thus we see that we as yet are far from the realization of the dreams of ,jules ,verne in his ,a ,voyage to the ,moon4 ,at any rate1 gravity on the ,moon is too weak to retain hydrogen over the hottest point of the surface4 ,this part of the gas flies away1 new supplies rush in from the sides1 and in a short time all traces of hydrogen have disappeared from the ,moon4 ,probably it was mainly gathered in by the ,sun1 where a velocity of #fac km4 7#chj miles7 per second is necessary if the molecules are to overcome the ,sun's attraction1 while their actual velocity there amounts to only about #h km4 7#e miles7 per second4 ,in a similar manner we find that the second lightest gas1 helium1 at a temperature of #aej ,c4 7#cjj ,f471 possesses a molecular velocity of #a4fb km4 7#a4a miles7 per second4 ,this is less than the #b km4 7#a4bd miles7 per second necessary to leave the ,moon's sphere of attraction4 ,but all helium molecules do not move at the same speed2 some are faster and some slower than the average4 ,those moving at a higher rate than #b km4 7#a4bd miles7 per second constitute a considerable fraction of the total4 ,this fraction disappears4 ,equilibrium is soon restored so that in less than a second the same fraction of helium molecules is ready to depart4 ,in this manner the ,moon lost its helium atmosphere speedily1 although not quite as rapidly as its hydrogen4 ,more slowly yet vanished the gases which are most abundant in our atmosphere1 nitrogen and oxygen1 but these too were not fettered for ever by the limited gravity on the ,moon4 ,the same fate befell aqueous vapour1 which is nearly twice as light as oxygen4 ,the loss of water1 however1 was long delayed1 as we later shall learn1 because new vapour masses were discharged from the lunar volcanoes4 ,in these considerations1 we should also bear in mind that the ,moon no doubt was a fluid molten mass when separating from the ,earth and its substance resembled the lava from our volcanoes4 ,in this condition it remained until its exterior temperature had fallen to about #abjj ,c4 7#bbjj ,f474 ,at that point1 the average velocity of oxygen molecules is about #a km4 74#fb mile7 per second1 with variations in both directions1 so that a few per cent4 of them reach a sufficient velocity to leave the ,moon for ever4 ,such gas molecules of medium weight return probably to the ,earth which1 as experience tells us1 is ponderous enough to hold them in bonds4 ,all gases1 that constitute any considerable fraction of the ,earth's atmosphere1 and which1 therefore1 most likely were divided with the ,moon in its parting from us1 have again left that globe4 ,the same unquestionably holds true for other stellar bodies of equal or smaller size1 such as all the minor planets and for the great majority of the satellites to the major ones4 ,only the very largest of ,jupiter's moons1 and possibly ,neptune's lonely companion1 whose size is not known with certainty1 might possibly surpass our ,moon in ability to retain gases4 ,our reasoning with respect to the ,moon applies also to ,mercury4 ,it is true that the molecules there must possess a velocity one and a half times as high as on the ,moon if they are to leave the planet4 ,but at the same time the temperature on ,mercury's hottest point1 always turned toward the ,sun1 is far higher1 about #djj ,c4 7#gej ,f471 so that the molecules there move #a4bf times as fast as similar molecules over the ,moon's hottest point4 ,mercury is consequently better able than the ,moon to retain gases1 but the difference is slight4 ,direct observations 7see below7 also lead us to believe that ,mercury is very similar to the ,moon in these respects4 ,we might possibly imagine that certain gases1 which on the ,moon would condense into fluids or solids1 on ,mercury might remain volatilized on account of the high temperature and thus form an atmosphere4 ,such assumption1 however1 would be erroneous4 ,the investigations by ,schiaparelli and by all his successors show that ,mercury in turning around its axis always presents the selfsame side to the ,sun4 ,the opposite side1 never reached by a ray of sunlight1 must assume an extremely low temperature1 very close to the absolute zero 7-#bgc4g ,c4 or -#dfj4f ,f47 and far below any cold existing on the ,moon4 ,to this side1 all bodies with an appreciable vapour pressure must distil and freeze to solid lumps or frost-coverings without perceptible vapour pressure4 ,for these reasons1 ,mercury cannot possess any atmosphere to speak of4 ,there remain in the whole series of planets and satellites in our solar system only two bodies besides the ,earth which are endowed with an atmosphere in the original sense of the word--namely1 ,mars and ,venus4 ,we reach the same conclusion when investigating the ability of the planets to reflect the sunlight falling upon them4 ,the bodies which possess an atmosphere hold also suspended therein clouds of water or ice1 and also of dust1 whirled up from below4 ,these floating particles reflect light far more efficiently than the solid or fluid surface of a planet4 ,the ,moon can now reflect #g4c per cent4 of the sunlight and ,mercury #f4i per cent4 7,h4 ,n4 ,russell1 ,proceedings ,nat4 ,acad41 #aiaf74 ,these numbers lie so close that they may be considered practically the same within errors of observation4 ,it is therefore probable that ,mercury is as devoid of an atmosphere as the ,moon4 ,the opposite extreme is represented by ,venus1 which reflects not less than #ei per cent4 of the sunlight received1 according to ,h4 ,n4 ,russell4 ,terrestrial clouds were found by ,abbot to return #fe per cent4 ,we believe from astronomical observations that the entire surface of ,venus is hidden behind a thick opaque cloud-covering4 ,the slight difference between ,o4#fe and ,o4#ei may be due to errors of observation1 but also to a small absorption of light in those parts of ,venus's atmosphere which are outside of the clouds4 ,saturn and ,jupiter are very similar to ,venus in this regard with #fc and #ef per cent4 respectively4 ,the gases above the clouds on these planets extinguish to a considerable extent the sunlight reflected from the clouds1 as apparent from their spectra4 7,compare ,fig4 #ac47 ,hence the value #j4fc given by ,russell for ,saturn is probably too high4 ,concerning ,jupiter it has been observed that its red light becomes deeper when the sunspots are few1 but whiter when the spots are numerous4 ,the sunspots have been found to favour the formation of high clouds1 such as cirrus1 and this would seem to apply also to ,jupiter2 when spots are plenty1 the clouds are high1 and consequently the absorbing layers above1 which cause the red colour1 are thinner1 so that ,jupiter will then shine with a whiter--less red--lustre than when the sunspots are rare4 ,the two outmost planets1 ,uranus and ,neptune1 return1 according to ,russell1 #fc and #gc per cent4 respectively of the sunlight received4 ,these figures are probably too high4 ,they do not agree well with ,slipher's records of their spectra 7,fig4 #ab74 ,there now remains ,mars4 ,this planet approaches the ,moon inasmuch as it reflects only #ae4d per cent4 of the sunlight arriving to the orb4 ,everything points to the conclusion that the atmosphere of ,mars is very thin4 ,lowell estimates1 on somewhat meagre grounds1 however1 that on each square metre of the planet rests only #bb per cent4 of the mass of air supported by each square metre of the ,earth's surface4 ,it would naturally be very interesting to ascertain the amount of sunlight our ,earth throws back into space4 ,this we cannot measure1 as we cannot place our instruments outside of the ,earth's cloud-mists nor can we read them there4 ,not less than #eb per cent4 of the ,earth is covered with clouds1 whose whiteness 7,latin3 ,albedo7 is #fe4 ,thus the clouds alone return #j4eb #j4fe #j4cch parts of the sunlight4 ,of this portion a fraction amounting to about #d per cent4 is extinguished in the air above4 ,the remainder is #j4cbe4 ,atmosphere and suspended dust reduce the sunlight over the cloud-free part1 i4 e4 #dh per cent4 of the ,earth1 by #fj per cent1 half of which returns to space1 while the other half reaches the ground in the form of light from the sky1 and of this fraction again about #d per cent4 is reflected into space2 these two items added give #j4ae4 ,finally1 the #dj per cent4 sunlight directly received by the ,earth's surface is reflected to the extent of #f per cent4 by the oceans and by the generally moist ground2 deserts and bare rocks reflect about twice as much1 but their total area is comparatively small2 of this #f per cent4 reflected light1 #gj per cent4 reaches outside space2 thus we obtain #j4dh #j4dj #j4jf #j4gj #j4jjh4 ,in all1 therefore1 the amount of reflected sunlight is #j4cch #j4ae #j4jjh #di4f per cent4 ,if the air were free from clouds1 the reflexion-number or ,albedo would be #cc per cent41 or considerably higher than that of ,mars4 ,when now half or a little more 7#eb7 of the ,earth's surface is overcast with clouds and this portion therefore has the whiteness of ,venus1 the figure #di4f 7,russell calculates the figure #de7 for the entire ,earth naturally falls closer--almost #c4f times--to #ei1 the figure of ,venus1 than to #ae4d1 the figure for ,mars4 ,we may also compare the value #cc per cent41 which applies to the cloud-free portion of the ,earth1 with the value #ae4d per cent4 for ,mars1 which is almost without clouds1 and with the value #g4c per cent4 for the ,moon1 which has neither clouds nor dust1 because it lacks an atmosphere4 ,we can then conclude that the atmosphere of our ,earth holds almost three times as much dust suspended over each square metre as does ,mars1 and this in spite of the smaller gravitational force on ,mars1 which is about #cg4e per cent4 of that on ,earth4 ,taking proper account of the low temperature on ,mars we may easily compute1 by means of a formula given by ,stokes1 that a particle of dust should sink #b4c times slower on ,mars than on ,earth4 ,when1 nevertheless and in spite of frequent but thin mists1 so few particles of dust float in the atmosphere of ,mars1 the conception inevitably comes to our mind that the air on that planet must be extremely rarefied so that the wind-puffs have little power to raise the dust from the ground4 ,lowell estimated the barometric pressure at the surface of ,mars to be about #fd mm4 7#b4eb inches71 and ,proctor gives about twice this figure4 ,there appears to be ground for considering already the former value too high2 both are very uncertain4 ,if we accept that of ,lowell1 we find that each square metre of the surface of ,mars supports a column of air1 whose mass is only about one-fifth of the mass resting on each square metre of ocean surface on ,earth4 ,illustration3 ,fig4 #ad4 ,the planet ,venus1 with sunlit atmosphere 7to the left71 as observed by ,langley at the ,venus passage ,december #f1 #ahhb4 ,the dense clouds which float above ,venus have long ago led to the assumption that the atmosphere of that planet must be far deeper than that of the ,earth4 ,its strong refractory power has also contributed to this belief4 ,when ,venus is close to the sun-disc the dark body stands forth surrounded by a ring of light 7see ,fig4 #ad74 ,it is1 however1 recognized that this phenomenon requires no greater air density than that on ,earth for its appearance4 ,in this connection we should remember that the inside limit of the vapour shell which we in this manner observe1 is the cloud-wall1 not the ground4 ,and these clouds1 we have every reason to believe1 float on account of the heat prevailing at a great height in the atmosphere1 so high in fact that they form an impenetrable wall already where the cirrus clouds appear in our sky4 ,if these suppositions are correct1 the light-ring mentioned is caused by a quarter only of the air-masses on ,venus1 and its total air-covering must be far deeper than that of the ,earth4 ,the latter occupies probably in this respect as well as in reference to position in space a middle ground between ,mars with its extremely thin and ,venus with its comparatively dense atmosphere4 ,if so1 we might expect the atmosphere on ,mercury to be denser yet1 while we already have seen that it is almost wholly lacking on that planet4 ,the explanation is that ,mercury has lost its spin around its own axis and therefore always presents the same side to the ,sun--just as the ,moon and probably all other satellites turn one side only toward their respective central bodies--hence the opposite side becomes so cold that all gases are there condensed to fluids or solids except the two most volatile ones1 hydrogen and helium1 which on the other hand leave the planet on its hot side4 ,if ,venus1 therefore1 as held by several astronomers from ,schiaparelli to ,lowell1 always turned one side only toward the ,sun1 this planet also would be without any perceptible air-covering4 ,according to investigations by ,bjelopolsky of ,venus's spectrum1 which investigations1 however1 are in complete disagreement with corresponding measurements by ,slipher1 that planet has a period of rotation on its own axis of about #bi hours4 ,this figure is very uncertain and a new determination is therefore highly desirable4 ,in order to understand the atmospheres of the planets1 it is of great interest to ascertain the composition of the air that surrounds the ,earth4 ,our knowledge in these matters has grown considerably of late4 ,we shall in the main follow the presentation by ,dr4 ,wegener of ,marburg4 ,we know at present with considerable accuracy which gases enter into the air4 ,besides the previously well-known nitrogen and oxygen which contribute the bulk1 #gh4a and #bj4i per cent4 respectively1 of the total volume at the earth's surface1 we find water vapour in proportions changing with localities and times1 and it is for this reason left out when fixing the various percentages2 further1 carbon dioxide #j4jc volume per cent4 and the rare gases discovered by ,rayleigh and ,ramsay1 argon1 #j4icb per cent41 neon #j4jjab per cent41 helium #j4jjjd per cent41 krypton #j4jjjjje per cent41 and xenon #j4jjjjjjf per cent4 ,each one of these constituents diminishes in quantity with height in accordance with the so-called barometer-formula and the rate is the more rapid the heavier the gas4 ,krypton and xenon1 therefore1 which are two and one half and four times heavier than oxygen1 occur mainly in the lower strata4 ,the percentage of helium on the other hand1 a gas eight times lighter than oxygen1 should increase rapidly with height4 ,if the air consisted of a mixture of oxygen and helium at #j ,c4 7#cb ,f47 the former would decrease to one half at an elevation of #e km4 7#c4a miles7 but the latter not before we had ascended #dj km4 7#be miles7 7eight times higher than for oxygen1 as the weights are in the ratio of #a to #h74 ,at that altitude1 oxygen would have decreased in the proportion #a3bh #a3bef4 ,when1 as actually is the case1 there is #ej1jjj times more oxygen than helium at the surface this ratio should decrease in the proportion #abh3a at a height of #dj km4 7#be miles74 ,ninety kilometers 7#ef miles7 above the surface helium should overbalance oxygen and thereafter rapidly gain in preponderance4 ,this holds true provided no agitation takes place in the form of vertical currents of air4 ,similar laws apply to all light gases which do not turn into fluids or solids at low temperatures4 ,aqueous vapour1 on the other hand1 which when cooled condenses to clouds1 diminishes much faster than the nearly twice as heavy oxygen1 because the temperature rapidly decreases as we move upward or at a rate of about #e ,c4 per km4 7#ad4e ,f4 per mile7 up to #b4e km4 7#a4e miles7 and of #h ,c4 per km4 7#bc ,f4 per mile7 at a height of #h4e km4 7#e4c miles74 ,the quantity of water vapour shrinks to one half at #a4i km4 7slightly more than a mile7 above ground4 ,carbon dioxide again follows the barometer-formula applicable to other gases because it occurs in such minute quantity that it never condenses to clouds4 ,in fact1 it is water vapour alone which must be treated as an exception4 ,carbon dioxide is nearly one and one half times heavier than the other gases of the atmosphere on an average4 ,it should therefore diminish in the proportion #a3ba4e #a3b4h in a vertical distance of #e km4 7#c4a miles7 while the density of the air decreases only in the ratio #a3b4 ,several determinations of the presence of carbon dioxide in the atmosphere as high up as #c4h km4 7#b4cc miles7 have been made1 by ,s4 ,a4 ,andree among others1 but the percentage of this gas remains constant within the errors of observation4 ,the same holds true to a height of #g km4 7#d4ce miles7 for the proportion between oxygen and nitrogen1 although we might have expected a perceptible change as oxygen is #ad per cent4 heavier than nitrogen4 ,how shall we explain this fact which seemingly contradicts the theory just advanced8 ,the explanation is quite simple4 ,the preceding statements hold true for a mass of air at perfect rest4 ,but1 if the air is violently agitated1 the composition becomes homogeneous all through4 ,we know that in the barometric cyclones and anticyclones strong rising and descending air currents flow4 ,the composition of the atmosphere1 therefore1 becomes the same as far up as this mixing action prevails4 ,these currents produce another effect1 namely1 a fall of temperature with rising height4 ,because when a gas is transported upward the surrounding pressure decreases1 resulting in expansion and consequent cooling4 ,it is well known that a gas is heated when 7rapidly7 compressed1 a quality formerly made use of in the pneumatic fire-tool to ignite tinder4 ,it is evident that conversely a gas must cool off when expanding4 ,if now the mixing of the air were extremely rapid the thermometer would fall very close to #aj ,c4 7#ah ,f47 with each km4 74#fb miles7 rise in elevation4 ,if1 on the other hand1 the air stood perfectly still in a vertical direction1 the temperature would remain constant at all heights over the same point4 ,between these two extremes1 we find the actual condition1 inasmuch as the temperature of the atmosphere decreases upward #e to #h ,c4 per km4 7#ad4e to #bc ,f4 per mile7 as observed during balloon ascensions4 ,this applies to the so-called 8troposphere0--mixing-zone4 ,one of the most remarkable discoveries in recent times1 made by ,teisserenc de ,bort and ,assman1 is the fact that the decrease of temperature with height does not continue indefinitely but only up to a certain elevation1--in middle ,europe about #aa km4 7#g miles71 in ,lapland about #g km4 7#d4e miles71 and at the equator about #ae km4 7#aj4e miles7--and above this point the temperature remains constant4 ,we now meet the peculiar condition that the temperature of this upper layer1 which is called stratosphere--8film-zone0--is lowest over the equator1 because it commences at a great height there1 and lowest over the polar regions1 where it extends farther down4 ,the stratosphere has received its name from the fact that it consists so to speak of lamell almost parallel to the earth's surface and moving in a horizontal direction while vertical motions are absent4 ,the winds in these strata have a marked westerly direction 7i4 e4 they are east winds7 and they become stronger the higher the stratum--at an altitude of #hc km4 7#eb4e miles7 their velocity is about #ajj m4 7#ccj ft47 per second4 ,in the troposphere on the other hand west winds predominate4 ,the wind direction in the stratosphere was observed on the so-called luminous night-clouds which were found as high as #hj km4 7#ej miles7 above the ,earth4 ,these strata consequently revolve slower around the earth's axis than the solid body of the planet itself4 ,at an elevation of #hj km4 7#ej miles7 the rotational speed has decreased to #fe per cent4 of the angular velocity of the earth's surface4 ,we have reason to believe that the very highest strata stand still1 that is do not take part in the earth's rotation on its axis4 ,this would follow if outside space were not entirely devoid of vapour so that our atmosphere would merge imperceptibly into the exceedingly attenuated gas masses of interplanetary space4 ,as high as the mixing-zone extends1 so high also is the composition of the air constant and like that at the surface of the earth4 ,but above this limit--in ,scandinavia1 we might say above an elevation of #aj km4 7#f4b miles7--commences a rapid tapering of the heavy gases1 while the percentage of the light ones correspondingly rises4 ,foremost among the latter is hydrogen1 with only half the weight of helium4 ,the presence of hydrogen in the atmosphere has been shown by ,boussingault1 and the proportion in which it occurs has later been measured by ,armand ,gautier4 ,it is about one three hundredth part of one per cent4 ,it increases extremely rapidly with height in the stratosphere so that #hj km4 7#ej miles7 above the earth and upward hydrogen is more abundant than all other known gases of the atmosphere at the same altitudes4 ,we reproduce below a somewhat revised table by ,dr4 ,wegener of ,marburg1 who has made the most recent computation of the percentages of the various constituents of air at different heights4 ,consideration has been given to the fact that the composition of the air does not change except as regards the percentage of moisture within the troposphere1 which is assumed to reach a height of #aj km4 7#f4b miles74 ,as usual in similar cases the percentages refer to volume4 ---------------------------------------- ------------------ ,height ,pressure ---------------------------- in in in in ,hydrogen ,helium ,nitrogen km4 miles mm4 inches #b #d #bh ---------------------------------------- ---------------- #j #j #gfj #bi4i #j4jjcc #j4jjje #gh4a ---------------------------------------- ---------------- #aj #f4b #aig #g4ge #j4jjcc #j4jjje #gh4a ---------------------------------------- ---------------- #cj #ah4f #h4ie 4#ceb ---- ---- #he ---------------------------------------- ---------------- #ej #ca4j #j4de 4#jagg #a ---- #hh ---------------------------------------- ---------------- #gj #dc4e #j4jde 4#jjagg #ac #a #hj ---------------------------------------- ---------------- #ij #ee4h #j4jaeg 4#jjjfb #fh #e #bf ---------------------------------------- ---------------- #aaj #fh4b #j4jaaf 4#jjjdf #id #e #a ---------------------------------------- ---------------- #acj #hj4f #j4jjig 4#jjjch #if #d #j ---------------------------------------- ---------------- #baj #acj4b #j4jjee 4#jjjbb #ii #a ---- ---------------------------------------- ---------------- #caj #aib4f #j4jjcb 4#jjjac #ajj ---- ---- ---------------------------------------- ---------------- #daj #bed4b #j4jjba 4#jjjjh #ajj ---- ---- ---------------------------------------- ---------------- #eaj #caf4b #j4jjaf 4#jjjjf #ajj ---- ---- ---------------------------------------- ---------------- ---------------------------------------- --------------------- ,height ,pressure ---------------------------- ,carbon in in in in ,oxygen ,argon ,dioxide ,water km4 miles mm4 inches #cb #ci4i #dd #ah ---------------------------------------- ------------------- #j #j #gfj #bi4i #bj4i #j4icg #j4jc #a4da ---------------------------------------- ------------------- #aj #f4b #aig #g4ge #bj4i #j4icg #j4jc #j4ad ---------------------------------------- ------------------- #cj #ah4f #h4ie 4#ceb #ae #j4bi #j4jjfd #j4e ---------------------------------------- ------------------- #ej #ca4j #j4de 4#jagg #aj #j4aj #j4jjad #a4g ---------------------------------------- ------------------- #gj #dc4e #j4jde 4#jjagg #f #j4je #j4jjje ---- ---------------------------------------- ------------------- #ij #ee4h #j4jaeg 4#jjjfb #a ---- ---- ---- ---------------------------------------- ------------------- #aaj #fh4b #j4jaaf 4#jjjdf #j ---- ---- ---- ---------------------------------------- ------------------- #acj #hj4f #j4jjig 4#jjjch ---- ---- ---- ---- ---------------------------------------- ------------------- #baj #acj4b #j4jjee 4#jjjbb ---- ---- ---- ---- ---------------------------------------- ------------------- #caj #aib4f #j4jjcb 4#jjjac ---- ---- ---- ---- ---------------------------------------- ------------------- #daj #bed4b #j4jjba 4#jjjjh ---- ---- ---- ---- ---------------------------------------- ------------------- #eaj #caf4b #j4jjaf 4#jjjjf ---- ---- ---- ---- ---------------------------------------- ------------------- ,under the name of each gas its molecular weight is given as a measure of corresponding specific weight4 ,the quantity of water vapour was not included when the percentages of the other gases were calculated1 because it changes considerably with locality and time4 ,the number given in the table for water is the mean for the entire globe--it corresponds to #aa4d grammes per cubic metre 74#ca oz4 per cu4 yd47--or the amount present in air saturated with moisture at #af4e ,c4 7#fa4g ,f474 ,the bulk of the water vapour forms a layer strongly concentrated toward the surface of the earth4 ,carbon dioxide also tapers rapidly with increasing height because its density is #a4e times greater than that of air4 ,this is apparent from the molecular weight #dd stated under carbon dioxide1 while the average molecular weight of air is #bi4 ,faster yet do krypton1 with a molecular weight of #hc1 and xenon1 with a molecular weight of #aca1 decrease as we ascend in the atmosphere4 ,these gases1 like neon1 whose percentage first increases slightly with height1 and argon1 which decreases upward as shown in the table1 do not perceptibly influence the processes of nature4 ,the reverse is true about water vapour and carbon dioxide1 which nourish the plants and also protect the ,earth against a too rapid heat radiation into space4 ,we well remember how abruptly the temperature changes in the course of the day in the dry desert climate1 while corresponding variation is comparatively slight in humid climates 7compare page #hf74 ,this is the result of the ability of water vapour to arrest the radiation from the ,earth4 ,carbon dioxide is about evenly distributed over the globe--although somewhat sparser over highlands--and its heat-conserving and equalizing influence is1 therefore1 not so manifest as that of moisture4 ,only by the most accurate investigations has this influence been demonstrated4 ,in ,wegener's table a gas is included1 called ,geocoronium1 whose existence in the air has not been directly proved4 ,conspicuous is1 however1 the green light displayed at great altitude by the ,northern ,light arches1 a green color which does not1 as far as we are aware1 belong to any known constituent of the air4 ,it is true that the corresponding spectral line 7#eeg 7 lies very close to a line belonging to krypton1 but the latter is a heavy gas which cannot occur to any traceable extent in the high strata1 more than #cjj km4 7#ahf miles7 above the earth1 where occasionally the ,northern ,light arches appear--their favoured height according to measurements by ,strmer is about #abj km4 7#ge miles74 ,wegener assumes1 therefore1 that this green line belongs to an hitherto unknown substance1 ,geocoronium1 which should be five times lighter than hydrogen4 ,recent researches present great difficulties to the acceptance of this assumption1 and for this reason further discussion of the problem will be omitted4 ,above a height of #baj km4 7#acj miles71 this gas1 according to ,wegener1 would preponderate4 ,if such postulated gas does not exist1 hydrogen completely dominates in these regions and down to #he km4 7#ec miles7 above the ,earth4 ,because hydrogen is so light1 the density of the air in the range of a barometric pressure below #j4jb mm4 74#jjjh inches7 increases but slowly as we descend toward the ,earth4 ,this uppermost part of the atmosphere may appropriately be designated as the hydrogen-zone4 ,even within this range1 the 8shooting stars0 meet sufficient resistance to flame into light at a height of about #abj km4 7#ge miles7 and dissolve into dust which turns dark about #he km4 7#ec miles7 above the ,earth4 ,e4 ,c4 ,pickering recognized the spectrum of hydrogen in the light of meteors passing at great height1 but decomposed water vapour might possibly be its source4 ,meteors crossing lower strata show the spectrum of nitrogen4 ,nitrogen becomes important from a height of about #he km4 7#ec miles7 downward and from #ge km4 7#df4e miles7 to the surface of the ,earth it predominates4 ,as a consequence the pressure increases rapidly as we approach the ground4 ,in these regions or up to #hj km4 7#ej miles7 floated the highest luminous night clouds1 observed by ,jesse1 indicating that here commenced a new range1 the nitrogen-zone4 ,only the heavy meteorites are able to penetrate into the nitrogen sphere1 which checks their speed and causes them to explode1 and thereafter the remnants fall with a velocity compatible with the air resistance they meet4 ,to these parts descend also the lowest rays of the ,northern ,lights1 the so-called draperies--,strmer observed them once at a height of #cg km4 7#bc miles74 ,finally1 water vapour presents itself in appreciable quantities at an elevation of about #aj km4 7#f4b miles71 where the troposphere commences4 ,we now meet the highest clouds1 cirrus 7with the exception of the 8luminous night clouds0 observed only in the years #ahhc-ahib after the eruption on ,krakatoa74 ,to these heights1 reach the vertical air currents which are essential to cloud formations4 ,only light clouds1 however1 float at these altitudes2 the heavy clouds 7alto-cumulus7 do not rise above #d to #e km4 7#b4e to #c4a miles7 and the rain clouds proper 7cumuli7 occur only below a height of #b km4 7#a4be miles74 ,this is the result of the downward concentration of water vapour within the troposphere4 ,if gravity decreased in intensity1 the effect would be the same as if the gases were lighter4 ,on ,venus1 the intensity of gravity is eight tenths of that on ,earth4 ,the difference is slight4 ,if everything else were similar the various air-zones would reach #be per cent4 higher on ,venus than they do on our globe4 ,but one essential condition is varied by the far higher temperature on our neighbour4 ,the proportion of moisture in the air is thereby vastly increased4 ,the dense clouds rise to much greater heights than on ,earth4 ,if there be ten times as much water in the air on ,venus as there is in the air on ,earth--which might fairly represent the actual condition--the heavy rainclouds would there rise to a height of more than #aj km4 7#f4b miles71 and their smaller weight on ,venus would also contribute to their buoyancy4 ,the light cirrus clouds should appear as high as about #cj km4 7#ah4e miles7 above the ground4 ,under such circumstances1 we cannot expect but that the planet must be entirely hidden from our sight as well as from the rays of the ,sun4 ,on ,mars1 the intensity of gravity is #b4fh times smaller than on ,earth4 ,in consequence barometric pressure falls #b4fh times slower with increasing height there than here4 ,the same ratio holds for decrease in temperature and for shrinkage of proportion of moisture when comparing conditions on the two planets4 ,the strong cold precludes anything but insignificant quantities of water vapour4 ,the air on ,mars is similar to the atmosphere on ,earth in and above the cirrus-region4 ,the clouds existing there are not only extremely thin and transparent--it is well known that cirrus clouds throw no shadows--but they are confined to small fractions of the planet's sky4 ,they are replaced by light mists4 ,we shall later return to the consequences of these peculiarities4 ,with help of the spectroscope we have ascertained that the gases on the ,sun are1 in the main1 also arranged according to specific weights1 so that the lightest reach the greatest heights4 ,somewhat similar conditions obtain in the gas-appendages of the stars 7compare page #aai74 ,,chapter ,v ,,the ,,chemistry ,,of ,,the ,,atmosphere ,of a very particular interest is the question of the atmosphere of the planets4 ,the great problem of habitability of the latter is most intimately connected therewith4 ,primitive fancy1 very early1 populated the stellar bodies1 especially the stars and the ,sun1 with beings similar to those on ,earth4 ,gradually1 however1 the insight awoke that these bodies are incandescent and therefore unfit to shelter life of the kind with which we are familiar4 ,attention then turned to the planets1 as they and the ,earth belonged to the same order of heavenly bodies4 ,perhaps they furnished abodes for our kin4 ,and the stars1 suns like our ,sun1 should not they be surrounded each with its throng of planets1 gravitating around their central source of light and heat8 ,this beautiful thought vied with the conception of ,earth as the centre of the universe and as wholly set apart from the other stellar bodies1 whose prime object it were merely to furnish light and to indicate time for the inhabitants of the ,earth4 ,much to be regretted1 it was the latter far less attractive theory which gained firm hold on the ,church1 although a few of its unbiased men1 like the renowned ,cardinal ,nicolaus ,cusanus 7#adja-adfd71 declared in favour of the contrary opinion1 and did so unmolested4 ,but times grew harder1 ironclad orthodoxy triumphed1 and ,giordano ,bruno1 whose defence was that he simply accepted the theory of the great ,cusanus1 was burned at the stake to expiate his fearless assertion that other worlds1 no less than ours1 might be blessed with the presence of living beings4 ,undoubtedly1 other planets are upbuilt of the same material which enters into the composition of the ,earth--as held already by ,leonardo da ,vinci4 ,spectral analysis teaches us that the same constituents form all the suns1 including our own4 ,if we agree that the suns have furnished the original substance of the planets revolving around them it is a natural conclusion that this matter should combine into similar chemical compounds on planets equally advanced in their evolutionary1 that is cooling1 process4 ,and we know1 indeed1 that the same elements compose the ,sun and the ,earth1 and that the samples brought to us from other worlds1 i4 e4 the meteors1 are of a composition which strongly reminds us of the rocks in the interior of the ,earth4 ,we seek in vain only for indications of the action of water1 which substance has left such obvious traces on the surface of our globe and in the immediate strata below4 ,but it should be remembered that the water1 in the form of vapour1 as previously set forth1 has left all the minor stellar bodies1 and the meteorites manifestly belong to the small or smallest among the wanderers of the heavens4 ,there is then no reason to doubt that the material of which the planets are built essentially is the same throughout the universe4 ,their interior should1 like that of our ,earth1 consist of the heavy metals1 principally iron1--strongly prevalent also in the ,sun and in the meteors1--and this metallic nucleus should be clothed with the silicates1 oxides1 carbonates1 sulphides1 and hydrates of all metals1 particularly aluminum1 and among the metals we may also count hydrogen4 ,the melting points of these exterior and lighter substances lies above #ajjj ,c 7#ahjj ,f474 ,no life could exist in such a molten mass1 so that not until a solid crust had been formed through cooling was the possibility of life at hand4 ,life is1 at least on ,earth1 tied to certain so-called compounds1 in which carbon is the essential common element1 while hydrogen1 nitrogen1 and oxygen together with sulphur1 phosphorus1 iron1 magnesium1 and a few other less important elements also enter therein4 ,no substance but carbon possesses this quality of being a prerequisite of life4 ,silica is a close kin to carbon and a substitute in certain organic compounds1 but protoplasm1 the main constituent of the living cell1 cannot be built without carbon4 ,in the inorganic world1 however1 silica by virtue of its affinity1 which is kindred to that of carbon1 plays a rle somewhat similar to the latter in the almost infinitely variably silicates4 ,protoplasm cannot endure in a temperature above #fj ,c4 7#adj ,f47 or thereabout--certain alg1 it is sometimes stated1 thrive in hot springs up to #hj to #ij ,c4 7#agf to #aid ,f47 but certainly not over #ajj ,c4 7#bab ,f474 ,at these temperatures--strictly speaking at all temperatures between ,o ,c4 7#cb ,f47 and #cfe ,c4 7#fhi ,f47--water can exist in fluid state and this too is a prerequisite of life4 ,we may say therefore that life is confined to a small temperature range between the freezing and boiling points of water4 ,but wherever water occurs1 except in a vessel which it completely fills1 there exists also in the adjacent space1 if unoccupied by fluids or solids1 water vapour of at least #d4f mm4 74#ah inches7 pressure4 ,there is1 therefore1 always an atmosphere of aqueous vapour on any planet whose surface is partly covered by water4 ,the palontologists have agreed that all life commenced in the water4 ,the manifold living beings which now inhabit the solid crust of the ,earth all descend from ancestors which floated in the waves of the ocean1 the cradle of all organisms4 ,it is not absolutely certain that oxygen is necessary to all living beings but many biologists hold that opinion4 ,certain bacteria are able to draw the oxygen they require for their development from compounds in which oxygen is bound sometimes in a very intimate manner1 as in sulphates4 ,but these bacteria are considered degenerate plants1 and free oxygen is certainly indispensable to the existence of the animals and probably also to the plants with the exception just mentioned4 ,as we shall see later1 free oxygen cannot be present on the planets until a solid crust has been formed4 ,we may therefore state that the conditions for the existence of life on a planet are fulfilled when a true atmosphere containing oxygen and water surround its body4 ,if we are to understand these conditions1 we must study the processes whereby oxygen is supplied to the atmosphere4 ,as the planets are segregations from the ,sun1 they should originally have the composition of the ,sun1 particularly that of its outer layers4 ,here metals occur in greatest abundance1 but there are also a few oxides1 especially those of titanium and magnesium 7according to ,fowler71 hydrogen in great quantities1 oxygen1 carbon1 cyanogen1 and carbon monoxide4 ,it may seem strange that free oxygen exists side by side with a surplus of hydrogen and sodium1 strong so-called reducing substances which bind oxygen4 ,but at the high temperatures prevailing on the ,sun compounds of oxygen and the reducing substances1 for instance hydrogen1 i4 e4 water1 are largely dissociated into their constituents4 ,but1 if the temperature should drop to about #abjj ,c4 7#bbjj ,f471 at which point crust building does not yet take place1 the oxygen would be entirely absorbed in the formation of the compounds mentioned4 ,the compound substances of the ,earth1 like those of the ,sun1 are also strongly reducing1 so that we must infer that free oxygen did not enter into the gas covering of the ,earth at the time when its solid crust was formed4 ,we may gain a conception of the gases which then existed in the outmost layers of the ,earth by studying the gases on the ,sun and on other stellar bodies1 particularly the comets1 and also by investigating the gases absorbed by the molten interior of the ,earth4 ,previous to the crust formation1 the entire mass of the ,earth except the gases in its outmost layers were of the same character as possessed by its molten interior now4 ,this molten mass1 or magma1 when in contact with the surrounding gases partly imbibed them through the process called absorption4 ,an investigation of the gases present in the magma will therefore give us an idea of those existing in the original vapours surrounding the ,earth4 ,the magma occasionally comes into view in volcanic eruptions1 and the confined gases are then partly given up into the air1 but they are also partly retained in the solidifying lava1 or volcanic rocks1 whence they may be driven off by high temperature and subsequently analyzed4 ,the direct gas emanations from the craters may also be gathered and analyzed4 ,such investigations have been carried out on a large scale by ,albert ,brun1 ,frenchman1 ,arthur ,day1 ,american1 and his co-labourers ,shepherd and ,perret4 ,brun reached the surprising conclusion that water vapour1 hitherto considered the most important of the volcanic gases1 in reality was not one of them but originated in the crust of the earth4 ,this theory1 however1 was completely refuted through the investigations by ,day and his associates4 ,as an example1 we give the analysis 7the mean of several determinations7 of volcanic gases from the crater ,halemaumau on the volcano ,kilauea in ,hawaii3 ,may1 #aiab ,per cent4 of ,volume ,carbon dioxide #ee4d ,carbon monoxide #d4c ,hydrogen #g4g ,nitrogen #bi4f ,sulphurous acid #b4i ,december1 #aiab ,per cent4 of ,weight ,carbon dioxide #db4i ,nitrogen #be4h ,water #bg4e ,sulphurous acid #c4g ,in the latter case1 it has been shown that air had gained entrance to the volcanic gases1 which air might have carried a quantity of water4 ,but this quantity could not have been large judging by the amount of nitrogen present which corresponds to not quite #c per cent4 water by weight4 ,in the former case water was not included in the analysis4 ,at any event1 a high percentage of water has frequently been observed in volcanic gases4 ,when the gases were left in contact with water a considerable part was absorbed thereby1 particularly compounds of chlorine and fluorine and also ammonia and sulphurous acid4 ,an analysis of such water showed #aj per cent4 more fluorine than sulphurous acid and two fifths as much chlorine as fluorine4 ,the ammonia amounted only to half of one per cent4 of the chlorine4 ,none of the rare air gases were present1 which indicates that the nitrogen originated entirely from the magma and not from the air4 ,brun has analyzed lavas from different volcanoes4 ,the gases extracted therefrom naturally do not give as reliable information about the original atmosphere of the ,earth as do the gases directly emanating from the volcanoes4 ,as examples we quote the composition of the vapours in lavas ejected ,march #d1 #aija1 from ,stromboli1 and from ,vesuvius in the well-known eruption of #aijf4 ,they show in percentages of volume3 ,stromboli ,vesuvius ,free chlorine #ab4h #j ,hydrate of chlorine #b4j #f4f ,sulphurous acid #d4e #ab4j ,carbon dioxide #fj4b #gc4h ,carbon monoxide #aa4e traces ,hydrogen #j4e #g4f ,nitrogen #f4i traces ,marsh-gas #a4f #j ----- ------ #ajj4j #ajj4j ,it will be noticed that the composition varies considerably4 ,free chlorine cannot very well be primigenial as it1 like oxygen1 combines with reducing substances4 ,chlorine may be produced by heating chloride of calcium with silica and ferro-silicates which are present in the magma4 ,at all events1 carbon dioxide constitutes the bulk4 ,next in importance are sulphurous acid and hydrate of chlorine4 ,carbon monoxide1 hydrogen1 and nitrogen may occur in quite considerable quantities but are sometimes almost wholly absent4 ,day and ,shepherd reached the conclusion that the gases emitted by the hot lava in the ,halemaumau crater are nitrogen1 water1 carbon dioxide1 carbon monoxide1 sulphurous acid1 hydrogen1 sulphur vapour1 also small quantities of chlorides1 fluorides1 and possibly ammonia4 ,such1 at least approximately1 should also the original composition of the ,earth's atmosphere have been when the crust was newly formed4 ,nitrogen1 water1 and carbon dioxide were the most important ingredients2 in the high strata hydrogen was present4 ,oxygen was totally lacking and reducing gases such as hydrogen1 sulphurous acid1 and carbon monoxide abounded instead4 ,if we further note the composition of comets and meteorites we find that cyanogen1 carbohydrates1 and carbon monoxide also are present in the former1 argon and helium in the latter4 ,it is therefore probable that these substances1 although absent in the emanations from ,kilauea1 yet belonged to the primary atmospheres of the planets4 ,the rare gases of the air especially should originally have come from the exterior parts of the sun1 as did the nitrogen4 ,an atmosphere of such a composition would be utterly unendurable to living beings4 ,it must1 if organisms are going to thrive therein1 be purified from such poisons as carbon dioxide1 gaseous sulphur1 cyanogen1 and sulphurous acid4 ,we know that such a process has taken place and that the sunlight has been the great chemist who produced oxygen and carbon from the carbon dioxide4 ,the just mentioned poisonous gases were subsequently oxidized through electrical discharges4 ,we all know that the plants up-build their framework under the influence of sunlight1 consuming in the meantime carbon dioxide1 water1 and a little ammonia4 ,in the process1 oxygen is formed1 as are also starch1 cellulose1 sugars1 and albuminous substances with the aid of the green colouring matter in plants1 chlorophyll1 which considerably accelerates the action4 ,subsequently these new substances1 which all 7except the albuminous ones7 belong to the carbohydrate group1 are converted into principally carbon and water4 ,the final result is that carbon dioxide through the agency of sunlight is split into its two constituents1 carbon and oxygen4 ,this process1 which is comparatively rapid in the presence of chlorophyll1 should also1 although more slowly1 take place without that medium2 and in recent trials the chemists--particularly ,daniel ,berthelot--have1 indeed succeeded in imitating without chlorophyll this important function of the plants through the application of light of a short wave length4 ,in the course of the many millions of years which geology has proved necessary for the evolution of our planet1 the carbon dioxide in the air was gradually converted into oxygen and carbon4 ,as long as reducing gases1 such as the poisonous ones mentioned1 or any considerable quantities of carbohydrates and hydrogen yet remained in the atmosphere1 the oxygen was consumed in their combustion4 ,if a solid crust had not existed to prevent the oxygen from entering into the interior molten mass1 it would also have found its way there and would have oxidized the reducing substances in the magma4 ,the separation of the interior from the surrounding gas shell is therefore a necessary requisite for the existence of free oxygen in the air4 ,another condition is that the combustible gases escaping from the volcanoes must be added to the air at a sufficiently slow rate not to consume all of the simultaneously formed oxygen4 ,a third requirement is that the liberated carbon should not in a renewed process of oxidation bind the oxygen just recovered4 ,as long as the air still was reducing1 this last condition was no doubt fulfilled for that very reason4 ,at all events1 the crust once formed and the original violent volcanic activity somewhat abated1 the time finally arrived when free oxygen existed in the air4 ,the previously present reducing gases were1 except for small fractions1 burned into water1 carbon dioxide1 and sulphuric acid and the nitrogen compounds had no doubt yielded free nitrogen to the stores of that gas already a part of the atmosphere4 ,the time was now ripe for the first plants1 probably low forms of alg1 which1 in the oceans1 commenced life on our planet4 ,the carbon dioxide and hydrochloric acid of the air as well as the newly formed sulphuric acid were absorbed by the running water and caused a rapid disintegration producing silica and acid silicates4 ,as plant life developed and extended the formation of oxygen increased4 ,falling vegetable matter was imbedded in slime which prevented the access of oxygen during decay and in this manner the fossil fuels were deposited4 ,koene of ,brussels first pointed out that the carbon and the sulphuric compounds accumulated in the ,earth would suffice to bind the oxygen of the air4 ,later investigations lead to the conclusion that the carbon alone is sufficient for the purpose4 ,it would therefore appear that all the oxygen of the air is derived from carbon dioxide belonging to the original atmosphere or contributed thereto by the volcanoes4 ,the reason why carbon dioxide and water continuously are liberated from the magma is undoubtedly that the acid silicates are lighter than the basic and therefore accumulate in the exterior parts of the magma4 ,a great surplus of silica exists there4 ,compounds containing water and carbon dioxide1 i4 e4 hydrates and carbonates1 are also light and should therefore congregate to the same strata where silica abounds1 there partly to be dissolved by the free silica and thus setting water and carbonic acid free4 ,the latter are1 in contrast to silica1 volatile and evaporate therefore into the air leaving the silica behind4 ,this process is yet in evidence wherever the magma emerges as through the volcanoes4 ,but also a few other acids in the magma are highly volatile1 as sulphurous1 thiosulphuric1 and hydrochloric acids4 ,these also belong to the volcanic gases1 are dissolved by the water1 and partake in the processes of disintegration4 ,the carbon dioxide and hydrochloric acid form carbonates and chlorides4 ,the former are extracted from the sea water by crustacea1 sometimes also by plants1 and form part of our sedimentary strata2 the latter are soluble and remain in the water1 chiefly as sodium chloride or common salt4 ,the thiosulphuric acid1 probably a product of ferrous sulphide and acids in the magma1 has entered into numerous insoluble metallic sulphides found in the ,earth4 ,partly1 it has also been oxidized1 like the sulphurous acid1 into sulphuric acid and has then assisted in the processes of disintegration1 forming gypsum which has been deposited in the sedimentary rocks4 ,the geologists believed formerly that the ,earth gradually and continuously has grown cooler4 ,this theory1 however1 struggled with the difficulty that certain cold time intervals1 ice periods1 were succeeded by warmer epochs4 ,to begin with efforts were made to surmount this obstacle by assuming that an ice period on the north hemisphere was counterbalanced by a warm period on the south hemisphere and vice versa4 ,in this manner1 the mean temperature for the entire surface of the globe might possibly have been continuously decreasing although fluctuations had occurred on the two hemispheres4 ,but this view has proved untenable1 because the ice period has left traces also within the tropics1 near the equator1 as on ,kilimanjaro1 in ,new ,guinea1 and so on4 ,it is now practically agreed that the last great ice period was characterized by a temperature between #d to #e ,c4 7#g to #i ,f47 below the present all over the surface of the ,earth4 ,this determination has been accomplished by measuring the difference in height between the terminals of the glaciers at present and the lowest points where their grinding action has left obvious traces4 ,the ice coverings of ,north ,europe1 ,north-,east ,america1 ,south ,america1 along the coast of ,chile and in ,argentina1 as well as on the southern island of ,new ,zealand1 all appear to have existed simultaneously4 ,also during earlier eras1 for instance during the ,algonkian and the ,permian epochs1 ice periods have occurred4 ,the latter1 which was felt in ,australia1 ,india1 and ,south ,africa1 is called the ,gondwana-time4 ,this period was formerly supposed not to have caused any temperature drop except in the tracts mentioned4 ,later investigations lead us to believe1 as asserted by ,holland in his presidential address to the geological section of the ,british ,association at its #aiad meeting1 that also this ice period simultaneously embraced the entire globe4 ,as the ,algonkian time belongs to the oldest epochs of geological history it appears that the temperature on the ,earth as long as life has existed on our planet on the whole has been nearly constant1 with important alternations1 however1 of warm and cold periods4 ,for an explanation of these fluctuations1 our well-nigh only recourse is the assumption that the heat-conserving quality of the atmosphere has changed by virtue of a varying composition4 ,warm periods occurred when carbon dioxide was abundant in the atmosphere due to volcanic activity1 cold periods again accompanied a paucity of carbon dioxide4 ,with rising temperature1 the percentage of water vapour in the air also increased1 affording further protection against radiation loss of heat4 ,thus1 it would seem as if the mean temperature of the ,earth's surface hardly had changed to any extent worth mentioning during immense spans of time estimated to about #ejj million years4 ,nevertheless1 a slow process of cooling proceeding toward the centre of the planet probably takes place4 ,ever growing quantities of matter are transported from the interior of the earth through volcanic action4 ,sedimentary deposits increase continuously while the interior becomes hollow4 ,as a result the crust must gradually settle1 causing large cracks in the process4 ,for these weakened places the volcanic products show a special liking and the craters are strung out in lines along such fissures4 ,in other places1 where volcanic action is less pronounced1 hot springs appear instead1 generally emitting carbon dioxide in abundance1 occasionally also sulphurous acid and sulphuretted hydrogen4 ,the dislocations in the crust also take place along these cracks accompanied by earthquakes4 ,the study of these various phenomena has enabled us to map out the fissures1 which generally radiate in nearly straight lines from one point1 the so-called centre of collapse1 as the cracks in a pane of glass issue from the point of breakage caused by a swift blow4 ,we shall later see that such breakage lines and centres of collapse are common on all stellar bodies which possess a solid crust and are observable from the ,earth4 ,we may now easily form an idea of the general trend in the development of the atmosphere4 ,the gases originally present were all1 except the hydrogen1 the nitrogen1 and the rare gases1 strongly absorbent of light and in particular of heat4 ,it is1 therefore1 natural that the planets which have not formed a solid crust possess a strongly absorbing vapour-shell1 as indeed is the case with the large planets 7compare ,fig4 #ac74 ,the crust once formed and the air gradually purged of these gases1 thanks to the sunlight1 so that mainly nitrogen and oxygen1 small quantities of the rare gases1 and carbon dioxide besides water remained1 the temperature fell rather rapidly4 ,carbon dioxide formed the last effective heat-conserving ingredient4 ,as the crust grew thicker1 the supply of this gas diminished and was further used up in the processes of disintegration4 ,as a consequence the temperature slowly decreased1 although decided fluctuations occurred with the changing volcanic activity during different periods4 ,supply and consumption of carbon dioxide fairly balanced as disintegration ran parallel with the proportion of this gas in the air4 ,but evolution on the whole can only proceed in one direction toward a final cooling of the ,earth4 ,this must occur if for no other reason because the store of energy in the ,sun and therefore its radiation must slowly decrease4 ,with deepening crust and disappearing carbon dioxide vegetation must ebb1 and with it the production of oxygen4 ,this gas also partakes in the general disintegration through oxidation of iron protoxides in the mineral rocks4 ,the oxygen portion of the air must therefore finally reach its maximum and start on the decline4 ,calculations point to the conclusion that the carbon dioxide of the air would be consumed in a few tens of thousand years if new supplies were not furnished from the interior4 ,water is also absorbed in the processes of decay as hydrated compounds are formed1 increasing in quantity with falling temperature4 ,as the amount of water in the ocean is immensely larger 7about #ej1jjj times7 than the stores of carbon dioxide in the air and in the seas the lack of the latter will undoubtedly first become serious4 ,but a slow desiccation of the planet must subsequently take place1 and will proceed at an accelerated rate with the continued cooling of the ,earth4 ,then the vapour in the air and consequently precipitation will wane4 ,then1 as during the ice periods1 mighty ice caps will cover the poles and impound a large portion of the water in the ocean4 ,finally1 the entire planet1 perhaps after having harboured life during trillions of years1 becomes an ice waste with a few cracks in its hard crust through which warm and acid vapours rise and create small melted areas characterized by a darker colour than the desert and ice-landscape in general4 ,organic life lacks the conditions for existence and ceases therefore to cheer the planet with its interesting variations4 ,the planet is dead but continues in obedience to gravitation to describe its orbit in space4 ,,chapter ,,vi ,,the ,,planet ,,mars ,through the works of ,schiaparelli1 ,flammarion1 and ,lowell the vivid interest of the general public has been directed toward our neighbour planet ,mars4 ,several investigators1 ,flammarion and ,lowell among them1 assert with full confidence that ,mars has intelligent inhabitants1 who have built and maintain the curious 8canals10 which1 it is stated1 could not have been created except by intelligent beings far superior to man4 ,air1 water1 and sunshine exist there1 says ,flammarion in his well-known great work1 ,la ,plante ,mars 7#aijb1 page #eae74 8,it appears incongruous to us to condemn a world like ,mars1 where all the conditions for life exist1 to such a fate0 7to be a dry desert74 ,no doubt sentiment and the desired result play a part in all such deductions1 as indeed the words chosen by ,flammarion would indicate4 ,as contrasted to the ,earth1 ,mars is1 on the other hand1 considerably further removed from the ,sun1 whose radiation therefore on ,mars possesses only #dc per cent4 of its intensity on ,earth4 ,judging by this fact1 the mean temperature of ,mars should fall far below that of the ,earth and considerably below the freezing point of water and under such conditions it is hard to imagine a vegetation near the poles of ,mars as ,lowell does in his volume1 ,mars as the ,abode of ,life 7#aiji71 or even in the neighbourhood of the canals anywhere on the surface of the planet as assumed by ,flammarion4 ,with such ideas in vogue we can well understand that the astronomers would point their lately extremely sharpened instruments toward our ruby-coloured neighbour in the sky when1 in #aiji1 it passed very close to the earth under conditions particularly favourable to accurate observations1 more so in fact than they had been during the seventeen preceding years4 ,numerous astro-physicists1 among them the world's foremost representatives of their discipline1 have repeatedly turned their spectroscopes toward ,mars in order to ascertain whether water vapour was present there or not4 ,in the spectrum of the ,sun we find several so-called 8rain-bands0 due to the fact that the light before it reaches the apparatus has passed through the moisture of the air4 ,the more humid the air the more strongly developed these rain-bands are4 ,if we direct the instrument first on the ,moon1 which lacks an atmosphere and therefore also moisture1 and then on ,mars1 which for the sake of simplicity we assume standing close to the ,moon-disk1 a difference should appear in the spectra of these two bodies1 provided moisture is present in the atmosphere of ,mars4 ,the rain-bands ought to be more pronounced in sunlight that has passed the atmosphere of ,mars 7passed it twice as the light is reflected by the surface of the planet7 than in light reflected from the naked ,moon4 ,the bands appear of course in both spectra as the light on its final stage to the spectroscope passes the atmosphere of the ,earth1 which never is free from moisture4 ,in this manner ,huggins and ,janssen1 scientists of world-wide fame1 believed that they had demonstrated the presence of water vapour on ,mars4 ,campbell1 on the other hand1 the prominent director of the ,lick ,observatory1 made similar investigations of the planet in #ahid1 and so did a ,french astronomer1 ,marchand1 in #ahif and #ahih1 both under unusually favourable circumstances as the former installed his instrument #abhc m4 7#ebjj ft47 and the latter #bhfj m4 7#icgj ft47 above sea level1 but neither found any indication of moisture in the atmosphere of ,mars4 ,it is evident that the observations would be far more accurate if we could eliminate the moisture from the atmosphere of the ,earth1 in which case no rain-bands would appear in the spectrum of the ,moon4 ,it would then be unnecessary to compare the two spectra2 we would only have to determine whether rain-bands were present in the spectrum of ,mars or not4 ,we can never entirely avoid the water vapour of the air1 but its influence may be greatly reduced by making our observations from high mountains or in desert climates where the air is comparatively dry1 that is free from water vapour4 ,investigations undertaken where the air is dry deserve therefore more confidence than those handicapped by greater humidity4 ,the observations by ,campbell and ,marchand fall in the former category1 and it would1 therefore1 appear that the presence of water vapour on ,mars to any extent worth mentioning is highly doubtful4 ,in later trials1 ,campbell and ,keeler have employed an improved method1 using photographs of the spectra on sensitive plates1 but neither has succeeded in discovering any water vapour in the atmosphere of ,mars4 ,obviously photography offers a great advantage over direct ocular observation4 ,the two pictures may be placed side by side and very accurate measurements may be made at leisure4 ,we may also choose the moments for exposure when the two stellar bodies stand equally high over the horizon so that the sunlight reflected from them traverses equal distances in the humid atmosphere of the earth4 ,it now devolved upon ,lowell to test his theories by means of the magnificent resources at his disposal in ,flagstaff observatory in the desert of ,arizona #bbjj m4 7#gbjj ft47 above sea level4 ,in the months of ,january and ,february the dew-point there is about -#g ,c4 7#ai4d ,f47 i4 e41 each cubic meter 7#a4c cu4 yds47 of air contains #b4h grammes 7#dc4be grains7 of water vapour while saturated air at zero temperature 7#cb ,f47 holds nearly twice this amount or #d4h grammes 7#gd grains7 per cubic meter 7#a4c cu4 yds474 ,slipher1 working in this observatory1 pushed the sensitiveness of his plates to the utmost then obtainable1 and photographed the spectrum of ,mars in ,january and ,february1 #aijh4 ,he found that the most important rain-band always was more prominent in the spectrum of ,mars than in the spectrum of the ,moon photographed later during the same night4 ,peculiarly enough1 it was only the rain-band designated 8,a10 and located in the red spectral field1 that was of a marked difference in the two spectra4 ,other bands gave no indication of the presence of water vapour on ,mars4 ,this result did not directly contradict the conclusions reached by ,campbell and ,keeler1 also by means of photography2 they had investigated other bands than 8,a40 ,the 8,a0-line might therefore possibly be more sensitive to water vapour than the others4 ,slipher's discovery was considered so valuable that it must be employed to the limit4 ,the well-known physicist ,very was therefore called in consultation2 he made careful measurements of the intensity of the 8,a0-lines on the various plates and calculated that the atmosphere of ,mars contained #a4ge times as much water vapour as that of the ,earth at the point of observation4 ,if we desire to determine the proportion of water vapour in the air at the surface of ,mars from this statement we may figure in the following manner4 ,the amount of water vapour in a vertical column of air one square meter 7#a4b sq4 yds47 in section is1 according to ,hann1 #bejj times the amount in a cubic meter 7#a4c cu4 yds47 at the surface of the earth4 ,at the time of the observation1 the latter amount was #b4bi grammes 7#ce4d grains72 on each square meter 7#a4b sq4 yds47 of the ground rested therefore #egbe grammes 7#ab lbs4 #aa oz47 of water vapour4 ,that the quantity of water is not larger1 although the depth of the atmosphere far exceeds #bejj m4 7#a4e miles71 is due to the fact that the temperature rapidly decreases with distance from the ground4 ,on ,mars1 the temperature ought not to fall so quickly with change in height because the intensity of gravity there is #b4fh times smaller than on the ,earth4 ,the temperature drops there #b4fh times slower with ascent in the atmosphere1 and a column of air on ,mars one square meter 7#a4b sq4 yds47 in section should therefore contain #ffhj times as much water vapour as a cubic meter 7#a4c cu4 yds47 at its surface4 ,as ,mars did not stand in zenith1 the distance traversed by the light-ray in the atmosphere was greater--in fact #a4dc times greater than if such had been the case4 ,a column of air in the direction of the light-ray1 one square meter 7#a4b sq4 yds47 in section contained therefore #hage grammes 7#ah lbs4 #c oz47 water vapour4 ,in the atmosphere of ,mars which the light passed in a vertical direction there was1 if we are to believe ,very1 #a4ge times as much1 or #ad1cjj grammes 7#ca lbs4 #h oz47 and in a cubic meter 7#a4c cu4 yds47 at the surface of the planet1 consequently #ffhj times less1 or #b4ad grammes 7#cc4a grains74 ,the corresponding dew-point is then1 according to this determination1 -#aj4c ,c4 7#ac4e ,f474 ,it is agreed upon that a desert climate prevails on ,mars4 ,it might at the time of the observation conform to the extremely dry climate at ,salt ,lake ,city in the height of summer when the humidity there is only #ca per cent4 of saturation4 ,under such conditions saturated air at noon in the equatorial belt on ,mars should contain #g grammes 7#ajh grains7 per cubic meter 7#a4c cu4 yds47 corresponding to a temperature of #e4c ,c4 7#da4e ,f474 ,it must be admitted that this was not very encouraging to ,lowell4 ,if the temperature in the middle of the day1 when the sunlight falls perpendicularly on the surface of the planet1 rises only to about #e ,c4 7#da ,f471 the mean temperature for twenty-four hours1 even in the midst of the summer1 must in this entirely clear1 light air be far below freezing and vegetation on ,mars is therefore not very well conceivable4 ,in spite of this1 ,lowell saw in ,slipher's measurements a confirmation of his theory that ,mars is the abode of an intelligent race that utilizes1 in their wrestle with existence1 a verdant vegetation pushed even into the polar regions4 ,campbell1 however1 went one step further than ,slipher4 ,in ,august and ,september1 #aiji1 ,mars occupied a position in the sky particularly favourable to observations4 ,campbell decided to benefit thereby4 ,with the support of a rich patron of science1 a ,mr4 ,crocker1 who on several occasions has made magnificent contributions toward astronomical research1 ,campbell equipped an expedition to ,mount ,whitney in ,california1 #ddbe m4 7#ad1ejb ft47 high and the loftiest peak in the ,united ,states4 ,he was accompanied by an able scientific staff1 the most prominent of which were ,dr4 ,abbot1 head of the observatory belonging to the ,smithsonian ,institution1 and a well-known ,german astronomer1 ,albrecht4 ,the members of the expedition were affected by mountain sickness and suffered many severe hardships when the wind was high1 reaching about #be m4 per sec4 7#ef miles per hour71 and at the same time cold1 falling below zero 7freezing7 during the night4 ,the barometric pressure was only #ddg mm4 7#ag4f inches74 ,during the nights1 when the observations were made1 the water content of the air fell to between #j4e and #j4i grammes 7#g4g grains to #ac4i grains7 per cubic meter 7#a4c cu4 yd47 or #b4e to #d times less than ,slipher had to contend with4 ,the spectra of the ,moon and of ,mars were photographed in close succession1 two exposures being made in each case4 ,the band 8,a0 was plainly visible on several plates4 ,no indication of greater prominence of this band in the spectrum of ,mars could be found4 ,other rain-bands were also investigated with the same result4 ,neither were the characteristic bands of oxygen stronger in the spectrum of ,mars1 than in that of the ,moon4 ,slipher believed that he had discerned a difference1 although of a hair's breadth1 which would indicate the presence of oxygen in the atmosphere of ,mars4 ,the conclusion itself is not improbable1 but the amount of oxygen there is in any case considerably smaller than in the ,earth's atmosphere4 ,several statements by ,campbell1 as well as ,slipher's observations1 indicate that a difference ought to have appeared between the spectrum of ,mars and that of the ,moon if the water content in ,mars' atmosphere had been the same as in the ,earth's at the time of the observation4 ,this content1 as stated before1 was about #c times smaller on ,mount ,whitney than at ,flagstaff4 ,at the latter place1 the measurements gave #a4ge as the ratio of water vapour on ,mars to that on the ,earth4 ,the amount of water vapour with the ,sun in zenith on ,mars should therefore1 according to ,campbell's observations1 only reach #j4d gramme 7#f4a grains7 per cubic meter 7#a4c cu4 yds47 corresponding to a dew-point of -#bh ,c4 7-#ah4d ,f47 or to an actual temperature of -#ag ,c4 7#a4d ,f47 allowing also for a desert climate with only #ca per cent4 saturation4 ,this temperature is probably higher than the mean for a summer day as the observations were made at noon on ,mars4 ,it must now be evident that we should consider ,mars as unfit to harbour living beings4 ,there is possibly a slight amount of oxygen in the thin air but the extremely low temperature and the scant supply of water vapour form insurmountable obstacles to the subsistence of even the simplest forms of life in the equatorial regions on ,mars4 ,the temperature difference between day and night must be enormous on account of the desert climate4 ,even if life could develop during the day1 which has nearly the same duration as with us--,lowell fixed it at #bd hours1 #cg minutes1 #bb4f seconds--and during which the temperature possibly might rise above the freezing point1 it would nevertheless be destroyed without mercy by the bitter frost at night4 ,campbell has offered an explanation of the indications of water vapour on ,mars1 apparent on ,slipher's photographs4 ,an analysis of the latter's observations shows that the ,moon was photographed about four hours later in the night than was ,mars4 ,on all occasions except one1 clouds appeared in the sky4 ,this indicates the presence of moisture in the air1 so that the humidity should change with the temperature which latter rapidly falls in the course of the night4 ,campbell1 himself1 found during the clear nights1 when he made his observations1 that the humidity in the hours of the night up to midnight falls to a fraction--a half or a third--of its original value an hour or so after sunset4 ,this rapid temperature drop is probably confined to the strata immediately above the observation point but the moisture is strongly concentrated downward so that this change in humidity undoubtedly should have been taken into account4 ,or better1 observations should be avoided in the beginning of the night and the ,moon and ,mars photographed as soon after each other as possible1 precautions taken by ,campbell but not by ,slipher4 ,that the latter found less traces of water on the lunar photos than on the martian ones is1 therefore1 probably due to the fact that the former were taken about midnight but the latter not long after sunset1 when the atmosphere contained much more water vapour4 ,thus1 we learn how a small slip1 more obvious to the meteorologist than to the astronomer1 may spoil a labour otherwise done with extraordinary care4 ,to ,campbell's critique ,very answered by the suggestion that the meteorological conditions during the ,mount ,whitney observations should have been exceptionally unfavourable4 ,the entire south-west of the ,united ,states and the north of ,mexico were visited at that time by cloudy weather and heavy downpours4 ,very contends that this humidity should partly have extended to the high strata above ,mount ,whitney and therefore rendered the calculation of the moisture content of the air entirely unreliable4 ,simultaneously 7,august1 #aiaj7 new measurements were published of ,slipher's photo-plates from ,february1 #aijh1 which ,very had examined4 ,the result was now that the rain-band 8,a0 was #b4e times more pronounced in the spectrum of ,mars than in that of the ,moon4 ,furthermore1 the oxygen absorption-band 8,b0 was #a4e times stronger for ,mars than for the ,moon4 ,great quantities of water vapour and oxygen should1 therefore1 undoubtedly exist in the atmosphere of ,mars4 ,in the meantime ,campbell had not been idle4 ,the difficulty with the older measurements consisted in the fact that the absorption line of water vapour in the atmosphere of ,mars occupies the identical place of the line due to vapour in the ,earth's atmosphere4 ,there exists1 however1 a method1 as already pointed out by ,campbell in #ahif1 of separating the two1 which method is available when ,mars either approaches or departs from the ,earth with sufficient velocity4 ,the latter could be determined both from the known motions of the two planets and from the displacement of certain spectral lines of the ,sun4 ,these two determinations were in almost perfect agreement2 for instance ,january #bf-bg1 #aiaj1 astronomical calculations gave a relative velocity of #ai4a km4 7#aa4hf miles7 per second and spectroscopical measurements #ai4b km4 7#aa4ic miles7 per second1 while on ,february #c-d the relative velocity was #ah4a km4 7#aa4bd miles7 a difference of #a km4 74#fb miles7 per second4 ,this trial shows the accuracy of the method4 ,among the absorption lines of water vapour and of oxygen there was1 however1 none due to the atmosphere of ,mars4 ,campbell assumes that such lines would certainly have been visible if they had been only one-fifth as strong as the so-called tellurian lines4 ,the advantage of this method is evidently that the 8martian0 and the 8tellurian0 lines lie close beside each other on the same plate so that differences in sensitiveness1 exposure1 and atmospheric conditions are entirely eliminated4 ,from these and the following data we may calculate water content and temperature of the atmosphere on ,mars anew3 water vapour at the point of observation was #a4i grammes 7#bi4c grains7 per cubic meter 7#a4c cu4 yds471 zenith-distance of ,mars #ee and incident as well as reflected sun-rays formed an angle of #gj with the surface of ,mars2 hence1 the amount of moisture at the surface was only #j4ab gramme 7#a4he grains7 per cubic meter 7#a4c cu4 yds471 corresponding to -#ch ,c4 7-#cf4d ,f47 for saturated air and to -#bg ,c4 7-#af4f ,f47 for air of #ca per cent4 saturation4 ,oxygen content per cubic meter 7#a4c cu4 yds47 at the surface of ,mars would be only a sixteenth part of corresponding numerical value on the ,earth4 ,this determination is more accurate than any of the previous ones and reduces the temperature another #aj ,c4 7#ah ,f47 below the lowest value derived earlier in this chapter4 ,we should remember1 however1 that1 during the trial of ,september1 #aiji1 the sun stood practically in zenith on ,mars1 while in ,january and ,february1 #aiaj1 we are concerned with a point where sunrise had occurred about four and a half hours previously4 ,the latter observation should give a value close to1 but slightly above1 the mean diurnal temperature on ,mars4 ,no determination comparable in precision with this one by ,campbell appears to have been made4 ,we must therefore recognize it as conclusive4 ,we may easily calculate the surface temperature of a planet from the intensity of the solar radiation received1 or insolation1 provided the surrounding vapour shell contains no heat retarding gas4 ,the most important gases of this kind are water vapour1 which1 as we just have seen1 is very sparse in the atmosphere of ,mars1 and carbon dioxide1 of which there probably also1 for reasons stated below1 is only a scant supply in the martian gas shell4 ,such calculations were first performed by ,christiansen of ,copenhagen1 who assumed #b4e calories as the solar constant on ,earth1 i4 e41 the amount of energy received through insolation per minute by each square centimeter 74#ae sq4 in47 of the ,earth's surface when at right angle to the radiation and on mean distance from the ,sun4 ,on ,mars1 the radiating energy received under similar conditions is only about #a4a calories4 ,the surface of the planet is heated until it radiates as much energy into space as it receives from the ,sun4 ,in this way we obtain an average temperature of -#cg ,c4 7-#cd4f ,f47 for the entire surface of ,mars4 ,the regions1 exposed to the ,sun in zenith at noon1 might1 if heat were not conveyed therefrom1 possibly reach a daily mean temperature of #h ,c4 7#df4d ,f47 and perhaps slightly more at noon4 ,probably not even the freezing point is reached1 as the heat is rapidly carried away by the freely circulating air4 ,the above-mentioned mean temperature of -#cg ,c4 7-#cd4f ,f47 seems on the whole to agree well with the observations by ,campbell on ,mount ,whitney4 ,recent accurate determinations of the intensity of the solar radiation by ,abbot1 ,k4 ngstrm and others1 indicate that it has been estimated about #bj per cent4 too high4 ,if we take the solar constant to an even #b4j calories1 which is a trifle high1 we reach the conclusion that the mean temperature on ,mars would fall about #ej degrees below freezing4 ,equatorial regions might then reach an average of -#h ,c4 7#ag4f ,f47 and at noon the temperature might possibly rise slightly above zero 7#cb ,f474 ,a higher temperature yet might be attained at the pole where the ,sun during the summer remains for months above the horizon or a high mark of #h ,c4 7#df4d ,f47 provided no heat were carried away by air currents4 ,such losses naturally must occur1 and the temperature probably hovers around freezing4 ,at the martian poles we might possibly imagine the existence of some low forms of vegetation 7snow-alg1 etc47 during the height of the short summer4 ,when we hitherto on the authority of ,lowell1 ,very1 and others1 have assumed an average temperature of #aj ,c4 7#ej ,f47 on ,mars1 we have done so on the supposition that the atmosphere of the planet contained great quantities of heat-conserving gases4 ,this assumption appears to be no more tenable than the belief in the high temperature on ,mars4 ,after all1 the temperature is probably about #aj ,c4 7#ah ,f47 higher than our last calculation would indicate--or about -#dj ,c4 7-#dj ,f47--because the air on ,mars is very clear and admits1 therefore1 all sun-rays1 retaining also a fraction by virtue of what little water vapour1 carbon dioxide1 and other heat-conserving gases there may be present in the atmosphere4 ,the mean summer temperature at the martian equator 7-#bg ,c4 or -#af4f ,f4 acc4 to ,campbell's data7 would then lie about #ac ,c4 7#bc4d ,f47 above the mean for the planet4 ,this agrees closely with conditions on the ,earth where the highest mean in ,july at the equator is #bg ,c4 7#hj4f ,f47 and the mean for the earth #af ,c4 7#fj4h ,f474 ,we are consequently obliged to revise in their entirety our ideas about ,mars4 ,the belief that organic life 7green vegetation7 causes the colour of the so-called seas on ,mars1 as assumed by ,lowell1 or that the red tints belong to the gorgeous dress in which autumn arrays the plants before their leaves are shed under the attacks of frost1 as intimated by ,flammarion1 must nowadays take its place in the shadowy realm of dreams4 ,those who do not believe that the so-called canals are real waterways1 devoted to freight carrying and irrigation1 or illusions1 which conception the photographs contradict 7for example ,fig4 #ah71 generally consider that they signify cracks or fissures4 ,as in the crust of the ,earth1 they generally run in nearly straight lines or in regularly bent curves 7,fig4 #ag and #ag;a74 ,flammarion mentions that the renowned physicist ,fizeau looked upon the 8canals0 as cracks in the ice-coverings of the oceans on ,mars4 ,penard1 in #ahhh1 expressed the more likely opinion that they correspond to the fissures in the crust of the ,earth4 ,flammarion contends that such fissures do not have the rectilinear configuration of the 8canals40 ,this is completely in error1 as shown on the map here reproduced 7,fig4 #af74 ,it is also stated that they are so inexplicably long1 for instance the canal ,phison is #bbej ,english miles 7,lowell7 or #cfbj km4 in length4 ,the longest known earthquake crack along the entire length of which a dislocation has taken place at one time is #fjj km4 7#cgc miles7 in extension2 the violent earthquake in ,california1 #aijf1 originated from this crack4 ,there is no doubt1 moreover1 that a great fissure in the ,earth follows the coast of ,chile from ,arica to the ,strait of ,magellan in a nearly north and south direction for a distance of about #cb parallels or #cefj km4 7#bbaj miles74 ,this fissure is almost as long as ,phison on ,mars4 ,such cracks exist along the entire coast of the ,pacific ,ocean4 ,as yet1 we do not know their position in much detail1 because long stretches run below the sea or through territories not yet occupied by civilized people4 ,as an example of a small fissure1 a picture taken by ,sederholm from ,segelskr1 east of ,hang in the ,baltic1 may serve 7see ,fig4 #ae74 ,as the studies of earthquakes are prosecuted with increasing interest in later years1 fissures of all dimensions will undoubtedly soon be discovered4 ,the solid crust on ,mars is1 furthermore1 somewhat thicker than that of the ,earth as the cooling of that planet has progressed further4 ,the sections broken off at the bursting of the ,martian crust ought therefore to be much larger both in breadth and in length4 ,no doubt1 the facts that the intensity of gravity on ,mars is only three-eights of its intensity on the ,earth and that the curvature of the ,martian surface is twice as sharp as the ,earth's contribute to this result4 ,imagine two vaults1 one built with higher and broader wedge-shaped stones than the other and with half the radius and furthermore loaded only one-third as heavily as the other1 and it will become evident that we can permit a much larger span in the former than in the latter case without fear of collapse4 ,in other words1 it requires a much more extensive caving or shrinkage of the molten mass beneath the crust of ,mars to cause a rupture than under the terrestrial crust4 ,illustration3 ,fig4 #ae4 ,narrow bay on the left side of ,segelskar1 east of ,hango in ,finland4 ,the bay owes its existence to the fact that the ice has laid bare a territory coursed through by fissures4 ,photo by ,i4 ,i4 ,sederholm4 ,illustration3 ,fig4 #af4 ,earthquake centres in ,calabria and in ,sicily4 ,on the larger map the damaged localities are indicated1 on the smaller the most prominent tremor lines4 ,drawn by ,i4 ,i4 ,sederholm4 ,as a consequence1 the fissures on ,mars ought to be longer than the corresponding formations on the ,earth4 ,a thorough study of the large fissure in ,calabria shows that it consists of a veritable network of smaller straight cracks 7as is apparent on ,figure #af1 which is taken from a work by the well-known ,finnish geologist ,sederholm74 ,on this map the radial cracks 7see ,worlds in the ,making1 ,fig4 #af71 charted by ,suess1 are also shown1 and their direction under the sea designated by dotted lines4 ,the sketch in the upper left corner of ,fig4 #af is in striking similarity to a picture drawn by ,schiaparelli in ,mercator's projection of the planet ,mars 7see map at the end of book74 ,we notice on both1 the numerous equidistant lines corresponding to parallel cracks and duplex canals4 ,not every fissure has its parallel and not every canal its mate--generally only one of the latter is visible and sometimes both disappear4 ,as the radial cracks in the drawing by ,suess if extended meet in the ,lipari ,islands1 so also several canals on ,mars run together in a so-called lake 7,lowell called them 8groves0 or 8oases07 which evidently is a centre of collapse 7many appear on ,fig4 #ag74 ,it is plain that all crossings of the 8canals0 are not necessarily such centres of collapse4 7,see maps ,figs4 #ag and #ag;a at end of book74 ,we shall consequently assume that the canals on ,mars correspond to the geological dislocation fissures on the ,earth4 ,along these fissures emerge the gases liberated in the cooling process on both planets2 which are similar gases to those which escape through the volcanoes4 ,these vapours are primarily water1 next carbon dioxide and1 in considerably smaller quantities1 sulphuretted gases and hydrochloric acid4 ,they discharge through cracks in regions which1 geologically speaking1 not so long ago were the scene of volcanic activity4 ,in the dislocation-grooves1 lakes1 and water courses are often formed1 as we may observe in several places in ,sweden1 for instance near ,stockholm4 ,assume now a gradual cooling of our earth4 ,most territories are covered by stratified1 comparatively light rocks4 ,to the dislocation fissures water gathers from the surrounding strata and occasionally from the interior1 partly washes away the loose material and transforms the fissures into furrows1 generally with flat bottoms4 ,dissolved salts are carried to the sea4 ,as cooling proceeds1 the ocean commences to freeze4 ,each summer the surface melts to a certain extent1 as is the case now in our polar regions4 ,finally1 the entire ocean freezes to the bottom1 the ice is now to be considered as a kind of rock1 flexures and dislocations cease and the ice assumes a smooth surface4 ,in the strong sunlight during the summer this surface thaws1 as do the water-courses on the mainland1 and these continue to carry their salts to the open surface water4 ,at the approach of winter the latter solidifies again but not as the water in our inland lakes from the top but from the bottom1 as ordinary sea-water possesses its greatest density below the freezing point while the opposite is true of fresh water4 ,the consequence is that the ice foundation grows upward and as the surface water becomes increasingly shallow it is turned into a concentrated salt solution4 ,with a further drop in temperature the ice formation is accompanied by crystallization of the salts4 ,something similar takes place on the ,martian mainland in its flat river basins1 which correspond to the salt lakes in our deserts4 ,on account of the bitter cold and the consumption of the water in the process of disintegration 7the carbon dioxide has been largely used up in the same manner71 precipitation has almost ceased on ,mars and most of the water in circulation emerges from the interior of the planet along the fissures4 ,as it contains hydrochloric acid and carbon dioxide it extracts from the soil salts1 such as the chlorides of sodium 7common salt71 of calcium and of magnesium1 all present in common sea-water to which it was brought by the rivers4 ,the compounds of calcium and magnesium are not precipitated as carbonated salts through the medium of crustacea as is the case on earth4 ,the strong solar radiation during the summer partly evaporates the water into the thin air1 leaving the salts behind4 ,on account of the low temperature1 this vaporization on ,mars is probably slower than on the ,earth4 ,along the cracks in the crust1 a kind of dry salt-lakes are formed similar to the generally shallow and occasionally dry lakes common in the deserts of ,central ,asia as described by ,hedin4 ,we know that ,mars possesses a pronounced desert climate4 ,there finally remains in the lowest sections of the water courses a concentrated salt solution1 which parts with its water more and more reluctantly1 so that the salts which most strongly hold the water crystallize at the deepest points4 ,if the winter's cold is sufficiently severe 7below -#ee ,c4 or -#fg ,f47 ice is extracted even from the most concentrated solutions1 which mainly contain chloride of calcium4 ,in spite of such extreme temperatures1 evaporation into the rare atmosphere is not negligible and the ice crystals partly vanish1 to reappear in the coldest regions of the planet1 that is1 around the pole which at the time is turned away from the sun4 ,on the ocean1 now frozen solid throughout1 a polar-cap of snow and hoar-frost is formed which finally reaches as far as the #chth parallel on the southern hemisphere 7see ,figs4 #ah and #ai71 where winter occurs when ,mars is most removed from the sun1 and to the #ehth parallel 7see ,fig4 #ai7 on the northern hemisphere where winter reigns while ,mars is nearest to the ,sun and consequently not quite so cold4 ,similar conditions obtain on the ,earth although not to such a marked degree4 ,illustration3 ,fig4 #ah4 ,photograph of ,mars1 enlarged and retouched2 taken by ,lampland ,illustration3 ,fig4 #ai4 ,appearance of ,mars ,april #h1 #aijg1 as observed by ,qunisset4 ,below one pole a dark line is plainly visible4 ,illustration3 ,fig4 #bj4 ,the south pole spot on ,mars observed by ,jarry-,desloges ,july #aj1 #aiji4 ,illustration3 ,fig4 #ba4 ,the appearance of ,mars during an observation by ,antoniadi in #aiji4 ,the whole disk is somewhat hazy2 below1 the details are hidden by clouds of sand4 ,in the vicinity of the snow-white polar cap1 whether there be continent or sea1 bodies of water occur with solidly frozen surface covered by crystals of very hygroscopic salts1 such as the chlorides of calcium1 magnesium1 and sodium4 ,when the summer warmth returns and the polar cap is heated1 the hoar-frost evaporates1 and the now comparatively humid air spreads over the surrounding territory4 ,we observe also frequent mist-formations in these places4 ,the ground near the edge of the polar snow assumes then often a dark hue on account of the moisture 7,fig4 #ai74 ,occasionally canals and lakes appear in the polar cap 7see ,fig4 #bj74 ,this is evidently due to hot emanations along the cracks4 ,the moist air sweeps over the salts1 which then absorb water and dissolve into concentrated solutions4 ,new quantities of water vapour are supplied from the pole as they distill over toward the other pole1 where winter now exists1 and push on toward the equator which they finally pass4 ,in their course they dissolve the salts in the depressions along the fissures and particularly at the deep crossings where the centres of collapse or the so-called 8oases0 are located4 ,lowell has observed that the 8canals0 in this manner gradually 8liquify0 from #gh ,n4 ,lat4 to the equator in fifty-two days4 ,the canal theory presents great difficulties to the explanation of this curious phenomenon4 ,in order to make the water flow it must be assumed that the surface of ,mars is entirely smooth or at least very nearly so and that the inhabitants convey the water melted at the poles through pumping stations4 ,the canals vary in width2 according to ,lowell1 their mean is #af km4 7#aj miles71 according to ,flammarion between #cjj and #fj km4 7#ahe and #cg miles7 which latter estimate probably is too high4 ,the same canal differs widely in breadth in successive years and sometime disappears altogether4 ,when the supply of water vapour is scant1 only the most hygroscopic salts are dissolved1 i4 e41 those deposited in the deepest furrow of the canal1 but when the moisture sweeping over the canal is more abundant the broader portions absorb water1 darken and thus become visible4 ,the same holds true in regard to the inland lakes 78oases074 ,as the water vapour diffuses in the air1 the canal becomes liquid along its entire length independent of the altitude of its various parts4 ,all agree upon the desert climate of the mainland on ,mars4 ,like most deserts on the ,earth1 it is1 therefore1 probably a table-land1 where one plateau mounts above the other1 each one nearly level4 ,by the action of the wind1 the upper layers have been transformed into fine sand4 ,on the dead planet no further sediments are deposited by the sea4 ,the only accretions to the planet are meteorites and cosmic dust which slowly rains down4 ,it contains among other substances iron1 partly metallic and partly in the form of protoxides 7which have a light green colour74#e ,the oxygen in the atmosphere of ,mars transforms these compounds to ferro-oxide which has different colours according to its coarseness1 but generally is ochre4 ,the surface of ,mars is also described as possessing this colour4 ,dross has1 therefore1 assumed that the ,martian soil is mingled with ferro-oxide4 ,the finest dust1 however1 is yellow while larger crystals tend toward violet4 ,we often observe on ,mars that the details are covered by a yellow veil4 ,this is of course finely powdered ferro-oxide probably mixed with less coloured sand which the desert wind whirls up over large portions of ,mars4 ,vast sections of the planet bore such wrappings in the autumn of #aiji1 as observed and described by ,antoniadi in ,paris 7see ,fig4 #ba74 ,similar observations have previously been made by ,w4 ,h4 ,pickering and others4 #e ,in the deepest portions of the oceans on the ,earth where no sediments from the coasts are deposited1 large accumulations containing iron compounds have been found and the presence of certain minerals therein points to their meteoric origin4 ,as a rule1 only the central and the polar regions of the surface of ,mars can be seen4 ,territories near the equator more than #dj to #ej degrees removed from the point in line with the ,sun and the centre of the planet are generally hidden behind a thin1 white veil of mist4 ,as soon as the ,sun leaves the zenith and reaches half-way to the horizon the moisture of the air is precipitated near the ground4 ,this shows that the planet does not possess any quantities of heat-conserving vapours in its gas shell4 ,the mist does not extend to the poles1 whose white caps always appear distinctly1 because the ,sun cannot greatly affect the evaporation in regions where the ,sun's altitude is neither very high nor very variable4 ,the same holds true for other snow-covered tracts1 even if they are not located in the immediate vicinity of the pole4 ,when the supply of water vapour is scant1 only the most salient canals come into view4 ,as a rule they do not then appear double1 as one of the mates is always less prominent4 ,lowell showed1 he believed1 that it always is the same canal out of a pair which first comes to sight and that its position always remains unchanged in contrast to ,schiaparelli who has reached the opposite conclusion4 ,this1 of course1 is quite natural4 ,on account of the small amount of water vapour in the atmosphere of ,mars true clouds are rare4 ,figure #bb shows such a cloud at the edge of the planet4 ,the aforementioned mists are often called clouds1 for instance by ,pickering4 ,illustration3 ,fig4 #bb4 ,cloud at the upper right edge of ,mars observed by ,molesworth1 ,march #g1 #aija ,illustration3 ,fig4 #bc4 ,mars as observed by ,lowell1 ,july #aa1 #aijg4 ,even the dark portions appear coursed through by 8canals40 ,illustration3 ,fig4 #bd4 ,mars1 as observed by ,e4 ,m4 ,antoniadi1 ,october #f1 #aiji4 ,that elevations really may be found on ,mars is evident from the fact that snow or hoar-frost often remains in patches near the pole and occasionally quite far therefrom1 for instance on the large island ,hellas 7#dj ,s4 ,lat471 while it disappears from the surroundings and sometimes from the pole itself 7the south pole74 ,such a highland covered by ice exists near the south pole1 and is shown near the upper edge of ,fig4 #bd4 ,in places where snow always remains1 a feeble glacier formation may occur4 ,most investigators assume that mountains and plateaus exist on ,mars1 although of modest altitude 7,campbell believes that he has observed peaks #cjjj m4 7#ihjj ft47 high74 ,lowell who diligently has looked for mountains at the edge of the illuminated part of ,mars1 has reached the conclusion that they1 if present1 cannot rise more than #fjj to #ijj m4 7#bjjj to #cjjj ft47 above the surrounding plains4 ,it were indeed improbable that all inequalities of the ,martian surface should have been removed in the process of disintegration1 which although at work for enormous extensions of time1 has long been extremely feeble and is unassisted by torrents of rain which might rapidly wash the products into the valleys4 ,at present1 it is mainly the sand carried by the desert wind that slowly reduces the roughnesses and in this process extensive highlands are hardly touched4 ,but1 without the assumption1 in itself very unlikely1 of a nearly level surface on ,mars it becomes difficult to comprehend how the canals1 if filled with pure water1 can proceed in straight lines without reference to existing differences in altitude4 ,like the rivers on the ,earth they ought to bend according to the topography1 even if constructed by engineers4 ,when the canals freeze at the approach of winter1 they invariably have been observed to disappear in company with the lakes or oases at their crossings4 ,they are then all covered by the reddish-yellow dust carried by wind from the surroundings4 ,when a canal is about to reappear it frequently first comes to sight as a dark streak evidently the result of moistened ferro-oxide4 ,occasionally a mist formation precedes the appearance of the canal4 ,it is plain that the cold1 misty air settles in the valleys1 there as here1 and gives up its moisture to the salts on their bottom and the canal is thus brought out as a dark line4 ,sometimes the vicinity also assumes a darker shade indicating the absorption of some moisture4 ,on the sides of the canals the less hygroscopic salts are deposited4 ,possibly the green colour of the canals is partly a contrast-effect due to the red surrounding1 possibly also the result of finely divided matter in the liquid4 ,it is also conceivable that the cause is the reducing influence on the ferro-oxide of the sulphuric gases emerging from the fissures2 an exceedingly small quantity accomplishes in this case large results4 ,f4 le ,coultre describes the colour as being sometimes a dead black4 ,something similar applies to the seas4 ,when these freeze1 especially in shallow places1 yellowish-red dust from the continent settles on their surface and lends it hues between the original dark green and the light yellowish-red4 ,when the ice subsequently melts this dust sinks in the water which latter resumes its dark green colour4 ,chloride solutions1 if concentrated1 freeze at the following temperatures2 that of calcium at -#ee ,c4 7-#fg ,f47 that of magnesium at -#dd ,c4 7-#dh4b ,f47 and that of sodium at -#bb ,c4 7-#g4f ,f474 ,if now1 as we previously have seen1 the mean temperature of ,mars as a whole is about -#dj ,c4 7-#dj ,f471 of the equatorial belt about -#aj ,c4 7#ad ,f471 and of the pole in the height of summer about #j ,c4 7#cb ,f471 it is evident that a liquefaction of the ocean surface and of the canals1 particularly where salts are deposited1 very readily may take place4 ,we should in this connection remember that the ice on ,mars is stationary while on ,earth it is in motion4 ,the consequence is that sand and dust in the course of thousands of years have accumulated on the bottom of the shallow basins in the polar ice4 ,these seas appear therefore dark in spite of their exceedingly small depth and the white salt and ice-crystals remaining undissolved are unable to display their light colour4 ,even in the 8ocean10 ,lowell was persuaded that he had observed canals 7see ,fig4 #bc71 and it may be possible that cracks are in evidence there1 particularly in the most shallow sections1 as is the case in the ,tyrrhenian sea north of ,sicily4 ,it is significant that ,flammarion has reached the conclusion1 which at first appears highly hazardous1 that the freezing point of water is lower on ,mars than on ,earth4 ,this is entirely correct1 if we let water stand for salt solutions4 ,it is customary to point to the strictly uniform breadth and the rectilinear appearance of the canals as clear evidence of their being artificial1 i4 e41 the work of engineers4 ,the ,italian astronomer ,cerulli strongly objected to this conception4 8,in the exceedingly rare cases when both sides of the canal plainly may be seen10 states ,schiaparelli1 8,i have observed curves and notches in the borders40 ,this occurred with the canals ,euphrates and ,triton in #ahgi1 and with the ,ganges in #ahhh4 ,and it would seem obvious that watercourses produced in old furrows would not1 as a rule1 be of uniform breadth4 ,antoniadi1 by his observations in the autumn of #aiji 7see ,fig4 #ag;a and #bd71 has confirmed this opinion1 as has le ,coultre1 who found twice as many irregular canals as rectilinear ones4 ,antoniadi remarks that some canals appear to be collections of lakes strung out in a certain direction while others are narrow lines which bend and twist4 8,the complicated network of straight lines is probably illusory40 ,the spots on ,mars1 he continues1 are very irregular1 and 8present by no means any geometrical form0 7on which the belief largely is founded that they are the product of intelligent beings74 8,the appearance of the planet reminds one of that of the ,moon 7except that the latter is dead1 i4 e41 unchangeable7 or of a terrestrial landscape viewed from a balloon40--8,in a word1 the #8geometry' of ,mars is revealed as a pure illusion40 ,exceedingly instructive is a comparison between the two maps of ,mars drawn by ,schiaparelli 7#ahhf7 and by ,antoniadi 7#aiji7 reproduced here and found at the end of the volume4 ,while ,schiaparelli as a rule represents the canals as narrow1 straight1 or slightly curved bands of uniform width1 these formations on the ,antoniadi chart frequently dissolve into a series of dark spots joined by less obscure sections 7see for example the canals ,nectar and ,oeroe at the ,sunlake74 ,the same is true about several of the so-called 8seas10 particularly the ,tyrrhenian 7,mare ,tyrrhenum71 and the ,sunlake 7,lacus ,solis72 also about the 8,ocean-bays0 such as the well-known ,syrtis major which with the ,sunlake form the most conspicuous objects on the surface of ,mars4 ,these maps are1 moreover1 of great interest because several canals and other features present on one are absent on the other and vice versa4 ,in this way1 we obtain a vivid conception of the remarkable changeableness of the ,martian surface as contrasted with the exterior of the ,earth4 ,the latter1 if viewed from ,mars1 would not have presented any noticeable change in historical time except for the seasonal variation of the snow fields4 ,this peculiarity of ,mars is only explained by the fact that the geographical features of that planet as a rule are surface formations of a slight depth and therefore subject to rapid transformations4 ,frequently1 large white spots suddenly appear1 especially near the lakes1 such as the spot at ,lake ,phnix near the centre of ,fig4 #bd which represents ,mars on ,october #f1 #aiji1 according to ,antoniadi4 ,these white spots disappear as suddenly as they show forth4 ,the white colour is probably due to a very thin snow or hoar-frost1 which is easily condensed in the vicinity of the lakes but which as readily vanishes at the approach of a warm draft or of sunshine4 ,occasionally1 dark spots on ,mars are described as dissolving under strong enlargement into dark and light squares giving the appearance of a chessboard4 ,this reminds one of the bayirs in ,turkestan 7see ,fig4 #i74 ,the collections of lakes along the cracks on ,mars which appear to us as 8canals0 are repeatedly filled up by sand and dried out4 ,they are revived through new depressions along the dislocation fissures1 corresponding to our earthquakes1 when vapours of water and other gases pour forth and condense to lakes in the deepest pockets of the fissures4 ,canals are therefore created rather rapidly1 sometimes over night1 and vanish occasionally as suddenly4 ,the most remarkable case of 8new0 canals was made known through a communication by ,lowell4 ,two new canals1 at the time the most conspicuous on the surface of ,mars1 were observed east of 8,syrtis magna0 on ,september #cj1 #aiji1 from ,flagstaff observatory1 when they also were photographed1 which precludes an illusion4 7,on the other hand there was no sign of the great canal ,amenthes1 shown on the map ,fig4 #ag1 a short distance to the left1 i4 e41 east of ,syrtis in the very section where the new canals were observed47 ,also two new oases through which the new slightly curved canals passed were observed for the first time1 as were also a few minor canals in the neighbourhood4 ,in #aiac1 the double canal thiops 7see map at ,long4 #bdj2 the canal is there single7 was rediscovered from the ,lowell observatory after an absence of fifteen years4 ,these data make it evident that one or possibly several rather strong earthquakes took place east of ,syrtis major just prior to ,september #cj1 #aiji with the two oases as centres of collapse4 ,the fissures now made visible have probably existed before but filled with sand and have now reappeared as a result of the condensation of water vapour when it emerged into the cold ,martian air4 ,this fact1 that the most prominent canals in such manner now suddenly appear and now as rapidly vanish1 ought to convince us beyond doubt that they are not magnificent products of engineering skill1 for the construction of which we should require centuries on the ,earth4 ,the theory that intelligent men exist on ,mars is very popular4 ,with its help everything may be explained1 particularly if we attribute an intelligence vastly superior to our own to these beings1 so that we not always are able to fathom the wisdom with which their canals are constructed4 ,the crossings of the latter are said to be cities 7,lowell7 fifty times greater than ,london4 ,the trouble with these 8explanations0 is that they explain anything1 and therefore in fact nothing4 ,if we would endeavour to understand the phenomena on ,mars1 we must in the first place avoid the formerly so popular principle of 8purposiveness0 which led even the most prominent scientists into so many amusing errors4 ,neither may we base our conceptions1 as does ,flammarion1 on the assumption of natural forces unknown to us1 no matter how much such a course may appeal to mystics4 ,only forces with which we are familiar can be resorted to1 if we really are to understand nature4 ,it seems to me that such method of research might with good results be applied also to the planet ,mars4 ,,chapter ,,vii ,,mercury1 ,,the ,,moon1 ,,and ,,venus ,the planet ,mercury probably resembles ,mars in many respects1 but differs particularly in lacking an atmosphere4 ,the fissures in the crust of the ,earth or of ,mars are as a rule rapidly filled and their contours largely hidden from sight by alluvium or sand carried by windstorms1 so that they reveal themselves only through tremors and various emanations along their course4 ,the fissures on ,mercury on the other hand must remain as yawning chasms4 ,it is probable that reducing gases stream out of these cracks as on ,earth1 and colour the environment in a darker shade than the other visible part of the planet's surface1 that is the hemisphere turned toward the ,sun4 ,not very volatile gases1 such as sal-ammoniac1 other chlorides and sulphur1 which on the ,earth are deposited inside the fissures1 may here spread over large areas and discolour surrounding territory1 particularly where iron compounds are present1 and1 under the attack of sulphur1 turn black4 ,lowell has made drawings of the dark spots visible on ,mercury1 one of which is reproduced as ,fig4 #be4 ,these spots lie1 as on ,antoniadi's drawing of the surface of ,mars 7,fig4 #ag;a71 arranged in lines which are almost straight or of a slight curvature only4 ,this seems to indicate that the spots belong to areas immediately adjoining enormous fissures4 ,according to ,lowell's drawing1 these cracks are far more regularly distributed on ,mercury than on ,mars4 ,very close to the centre of the ever-sunny side we see a dark spot1 a 8lake40 ,it is evident that this spot is located in by far the hottest point on the surface of ,mercury4 ,this gives rise to the following conception4 ,the hottest part of ,mercury was naturally the last to solidify4 ,mercury evidently ceased to rotate around its own axis1 leaving one side continually exposed to the ,sun1 while its surface yet consisted of lava that was fluid1 at least where the sunshine was most intense4 ,the weakest point on the planet was therefore the one just opposite the ,sun4 ,when later collapses occurred the cracks commenced at this weak point4 ,we see on the figure how not less than six fissures radiate from this centre4 ,others were formed where the crust broke off from adjacent solid portions4 ,these latter fissures have a less rectilinear appearance than those diverging from the centre of collapse4 ,along these faults1 reducing gases no doubt issue from the interior of the planet and give a dark tone to the surface layers1 which probably consist of ferruginous dust falling from space4 ,in the neighbourhood of the ,sun1 such dust ought to be more plentiful1 concentrated as it were by the gravitation of the ,sun4 ,mercury lies five times nearer the ,sun than the ,earth does1 and twelve times nearer than ,mars4 ,there probably also exist on ,mercury1 as on the ,moon1 large mountains which are not subject to the wear of running water and blowing sand4 ,we cannot1 however1 observe them from the ,earth4 ,possibly they correspond to the widely extended spots1 which several investigators as ,schroeter1 ,vogel1 and others1 have noticed1 formations resembling the 8seas0 on the ,moon4 ,vogel believed that he had found traces of water vapour in the atmosphere of ,mercury as in that of ,mars1 a belief in both cases undoubtedly founded on erroneous observations4 ,illustration3 ,fig4 #be4 ,drawing by ,lowell1 representing the planet ,mercury with 8canals40 ,illustration3 ,fig4 #bf4 ,a part of the moon near its south pole4 ,the big crater above1 in the interior and on the walls of which a large number of smaller craters appear1 is ,clavius4 ,a little below and to the right is ,longomontanus just at the edge of the shadow2 almost in the middle of the picture appears ,tycho with its central cone4 ,the moon diameter corresponds to #dc4d cm4 ,photo by ,yerkes ,observatory4 ,illustration3 ,fig4 #bg4 ,mare ,serenitatis 7below71 ,mare ,tranquillitatis 7upper left7 and vicinity4 ,to the left of ,mare ,serenitatis the great crater ,posidonius2 #b4h cm4 from the right edge a small white spot may be seen4 ,this is the remarkable crater ,linn1 said to have undergone changes4 ,the moon diameter corresponds to #ce4g cm4 ,photo by ,yerkes ,observatory4 ,the part of ,mercury which is turned from the ,sun must be characterized by a tremendous cold due to radiation into space4 ,the temperature stays probably about #bjj ,c4 7#cfj ,f47 below the freezing point of water 7#cbh below zero ,f474 ,even the most concentrated solutions we know of freeze to ice precipitating the salt considerably above this temperature4 ,moisture in fluid state can1 therefore1 not very well exist on this side4 ,on the sunny hemisphere it must be lacking as well1 due to evaporation over to the cold side4 ,as a result1 the desolation on ,mercury must be far greater than that on ,mars and surface changes caused by variations in temperature are almost precluded4 ,on account of the so-called libration1 certain dark portions near the boundary of the illuminated hemisphere occasionally enter the sunlight4 ,but1 during this interval1 all traces of moisture are undoubtedly driven away from these parts1 also never to return4 ,the ,earth's moon is not entirely as stagnant as ,mercury1 although on the whole it closely resembles this planet4 ,the ,moon always turns the same side to the ,earth--a small libration exists here also--so that each part of its surface is illumined by the ,sun during one half of the synodical month 7#bi4ec days74 ,this time1 however1 is so long that the moon's surface in the meantime almost assumes the temperatures due to continuous sunlight and continuous night4 ,some investigators1 as ,w4 ,h4 ,pickering1 are persuaded that portions of the moon just emerged from the shadow show a lighter colour than after a short time of illumination4 ,these observations1 however1 have not been accepted as correct4 ,according to ,pickering1 the light colour should result from a slight formation of snow or hoar-frost during the long night of #cee hours4 ,if an appreciable trace of vapour existed on the ,moon1 it ought to evaporate and form white caps over the poles where the ,sun's heat is not sufficiently strong to melt them4 ,as no such signs have ever been observed1 the faith in snow on the ,moon is not likely to find many defenders4 ,the lunar mountains are not attacked by water or sandstorms1 nor do they peel off due to rapid heating by the ,sun4 ,they rise1 therefore1 to full stature over their surroundings4 ,their height can be measured by the length of their shadows4 ,mdler1 in this manner1 computed one of the peaks of the ,mountain ,newton to rise #gcjj m4 7#bd1jjj ft47 above the territory on which its shadow falls4 ,six peaks reach between #fjjj and #gjjj m4 7#ai1ejj and #bd1jjj ft471 #ba between #ejjj and #fjjj m4 7#af1ejj and #ai1ejj ft471 #hb between #djjj and #ejjj m4 7#ac1jjj and #af1ejj ft471 and #ehb reach #bjjj m4 7#fejj ft47 and more4 ,these figures show the extraordinary mountainous character of the ,moon's surface compared to that of the ,earth which is thirteen times larger4 ,in ,fig4 #bf1 we see a picture of the portion of the ,moon most rich in volcanoes1 with the crater ,tycho in the centre and ,clavius above4 ,the numerous volcanoes are particularly characteristic of the ,moon4 ,they vary in magnitude from a diameter of over #bjj km4 7#abe miles71 for example the colossal ,clavius with its companion craters1 down to dimensions just visible with the aid of a telescope4 ,the largest exceed our biggest many times in width and differ essentially from them1 inasmuch as their bottoms are flat1 occasionally provided with smaller volcanic cones--see the crater ,longomontanus to the right of ,tycho on ,fig4 #bf--;and surrounded by a high 7inwardly often very steep1 outwardly more sloping7 wall as on ,clavius1 ,longomontanus1 and ,tycho4 ,the largest1 as for example ,clavius1 may be compared to a province such as ,bohemia1 surrounded as it is on all sides by mountains4 ,the elevated ring1 as well as the interior of ,clavius1 is adorned with numerous large and small craters4 ,the smallest of these resemble hemispherical excavations in the crust of the ,moon1 or they may be small volcanic cones which break through the walls4 ,sometimes they are strung out like pearls along rents in the ground4 ,all these volcanoes have undoubtedly given passage from the interior to the surface of the ,moon for enormous volumes of gases previously enclosed in the lunar magma4 ,nor is it less certain that these gases have consisted largely of water vapour4 ,if this had been condensed to water1 oceans and rivers would have been formed1 and on the bottom of the seas would have been deposited sediments carried down from the mountains4 ,such1 however1 is not the case4 ,the so-called 8seas0 on the ,moon are indeed on a lower level than their surroundings1 but their surface is even 7see ,fig4 #bg with ,mare ,serenitatis below and ,mare ,tranquillitatis above to the left2 see also ,fig4 #bi with ,mare ,imbrium below2 it is bounded on the right by the 8,carpathians074 ,the 8seas0 consist of volcanic rocks1 and are not at all covered with loose sediments which if present ought to reflect light better than the volcanic vitreous rocks4 ,but the lunar 8seas0 are much darker than the environments4 ,this shows that seas proper1 or bodies of water1 have probably never existed on the ,moon4 ,even before the surface had changed from its molten condition the water vapour had departed from the atmosphere1 and the new quantities which the volcanoes emitted from the depths below disappeared so rapidly that lakes were never formed4 ,the history of other atmospheric gases on the ,moon was no doubt similar4 ,all evidence1 therefore1 points to the conclusion that life never inhabited its rough surface4 ,fig4 #bg shows that the 8sea-bottoms0 are not free from volcanoes4 ,they also abound in folds1 corresponding to mountain-chains on the ,earth4 ,these folds indicate old breaks in the crust while it was yet very thin4 ,to the right1 in ,mare ,serenitatis1 appear a few white spots which ,w4 ,h4 ,pickering ascribed to snow4 ,the largest is the much discussed 8crater0 787 ,linn4 ,mare ,serenitatis is surrounded by a ring of volcanoes4 ,a noted astronomer1 ,cerulli1 observed1 when he directed a glass of moderate power1 such as opera glasses1 toward the ,moon that the spots seemingly arranged themselves in rows forming intersecting lines similar to the canal-system on ,mars4 ,as the regularity disappeared with greater enlargement1 ,cerulli believed that the canal-system on ,mars also would dissolve into small spots if a sufficiently powerful telescope were used4 ,his idea1 which partly has been verified1 was more recently adopted by the ,englishman1 ,maunder1 who denies the existence of canals on ,mars4 ,photography1 however1 has proved their reality 7,fig4 #ah74 ,if we disregard the illusory reticulation1 there are nevertheless on the surface of the ,moon numerous designs of a nearly rectilinear outline4 ,there are to begin with the sinuses1 extended trenches1 often dotted along their sides with minor volcanoes4 ,fig4 #bg shows1 in the upper right corner1 two such sinuses1 the right one with a small volcano1 ,hyginus1 in the middle4 ,there are1 further1 five such volcanoes in its left arm1 not visible on the photograph1 and two in the right arm4 ,the second1 8,sinus ,ariadaeus10 commences to the left with the ,volcano ,ariadaeus1 not visible on the figure4 ,the explanation of the origin of these sinuses is probably to be found in the different contraction of the ,moon's surface layer and of the hotter substrata immediately after the solid crust was formed4 ,in a way1 they correspond therefore to cracks in the glazing on porcelain4 ,like the two sinuses just mentioned they frequently commence and end with small craters which formed weak spots in the crust that facilitated the original break4 ,later on1 volcanoes broke through along the sinuses themselves4 ,in several regions of the ,moon1 and particularly in the equatorial belt1 observers have claimed discoveries of new sinuses and occasionally of minor craters1 8which could not possibly have escaped notice if they had existed before40 ,at present1 the almost unanimous verdict is that such changes are very improbable1 and that the visibility of the 8new0 objects largely depends on favourable sidelight1 so that they might well have been overlooked if the region in question previously was examined under less advantageous illumination4 ,the most peculiar formations on the ,moon are the so-called 8bright streaks0 which as a rule issue in almost straight lines from some of the larger craters1 particularly ,tycho and ,copernicus4 ,those around ,tycho 7see ,fig4 #bh7 do not seem to be either raised above nor depressed below the surroundings to any degree worth mentioning4 ,for this reason they are not visible under oblique illumination as in ,fig4 #be4 ,they proceed in straight lines independent of elevations4 ,this quality is in striking conformity with the characteristics of fissures on earth as for instance those that traverse the ,tyrrhenian ,sea and the ,calabrian mountains4 ,they also resemble the canals on ,mars in this respect4 ,nasmyth and ,carpenter caused a glass ball1 containing water under pressure1 to break at one point and obtained a system of beams radiating from this point and vividly reminding of the streaks around the lunar craters4 ,the same effect appears if a homogeneous plate1 of glass for instance1 is broken by a blow in one point4 ,no doubt these streak centres were once centres of collapse although they sometimes now are found at a considerable elevation1 like ,tycho4 ,this may be the result of a later secular lifting of the rocky substrata like the slow rise of the ,scandinavian peninsula4 ,the streaks around ,copernicus 7see ,fig4 #bi7 are very different from those around ,tycho4 ,they are not rectilinear and consist next to the crater of distinct mountain chains plainly visible under oblique illumination4 ,they penetrate into ,mare ,imbrium 7,fig4 #bi below7 crossing the mighty 8,carpathian0 mountains4 ,frequently1 they are provided with minor volcanoes1 as in the streak directed almost straight downward on the figure1 i4 e41 to the north4 ,they are obviously volcanic fissures like those on the ,earth4 ,illustration3 ,fig4 #bh4 ,tycho in full illumination with surrounding magnificent system of streaks4 ,in the lower right corner ,copernicus with a less regular system appears4 ,between them ,mare ,nubium1 in the upper right ,mare ,humonum1 with the great crater ,gassendi below4 ,the moon diameter corresponds to #af4g cm4 ,photo by ,yerkes ,observatory4 ,compare ,figs4 #be and #bh1 showing parts of the same territory under side light4 ,the streaks1 in many cases1 would not be visible at all were it not for their different colour1 which is considerably lighter than that of the surroundings4 ,the only explanation offered for this fact is the assumption that the original cracks were filled by some light matter forced out from the interior of the ,moon1 that is by the lunar magma4 ,this magma was not very viscous1 as it has spread out considerably beyond the edges of the cracks proper4 ,these presumably1 like those on ,earth1 were of a rather moderate width1 not enough to be distinguishable at the ,moon's distance4 ,similar light-flowing emanations from long fissures are known also on our planet1 for instance1 from the ,laki eruption on ,iceland in #aghc4 ,the colour may be light simply by comparison with the previously solidified crust1 which1 optically1 as regards reflexion of light1 has proved very similar to obsidian or1 even more like another volcanic mineral product1 vitrophyre4 ,it is also possible1 however1 that gas bubbles were liberated as the lava solidified and gave the surface a milkwhite appearance--gravity on the ,moon is only one sixth of that on the ,earth so that the bubbles would rise and evaporate extremely slowly from the magma4 ,due to the very low atmospheric pressure on the ,moon1 the bubbles would also occupy a larger volume than in a corresponding case on ,earth and become more conspicuous in proportion4 ,they probably partly remained on the surface of the outpoured lava as a thin scum1 which hardened in that state4 ,since then1 it has suffered no more change than all other formations on the ,moon1 while on the ,earth it would soon have been scoured away by sand and water4 ,illustration3 ,fig4 #bi4 ,the great lunar crater ,copernicus surrounded with streaks4 ,below the ,carpathian mountain range and at bottom part of ,mare ,imbrium4 ,the moon diameter corresponds to #ee cm4 ,photo by ,yerkes ,observatory4 ,before we leave the ,moon it may be well to say a few words about its colour4 ,mdler states in agreement with several other observers that ,mare ,serenitatis1 a 8sea0 on the ,moon's north side 7#be latitude7 just to the right of the centre meridian 7see ,fig4 #bg7 is remarkable for its beautiful pure green colour1 while ,mare ,crisium about #af ,lat4 ,n4 near the right edge of the ,moon is of a dark grey-green hue4 ,in ,mare ,humorum 7about #bb ,lat4 ,s41 not far from the edge of the ,moon1 see ,fig4 #bh7 grey and dark green shades alternate and in ,mare ,frigoris1 just inside the lunar north pole1 the colour is a dingy yellowish-green4 ,in other words1 the characteristic colour of the great lava seas is apparently green4 ,this agrees closely with conditions on the ,earth where similar formations are coloured green by silicates of ferrous protoxides1 certain species of which are called green-stones4 ,franz1 however1 questions the observations of ,mdler and professes the belief that very light craters appear bluish and assumes this to be a contrast effect to the general yellow hue of the ,moon4 ,langley investigated the lunar radiation with the spectroscope and found that the ratio of blue to yellow was smaller in the moonlight than in the sunlight1 for which reason the general colour of the moon resembles that of yellow sandstone4 ,a very interesting observation was made at the ,lowell observatory when investigating the spectrum of the sparse light reflected from the ,earth to the portions of the ,moon not exposed to the sunlight4 ,it proved to be of a far more blue tinge than sunlight reflected from the ,moon4 ,our conclusion must be that the ,earth shines with a blue lustre4 ,this is perfectly natural1 as the diffused light which reaches us after having been scattered by particles suspended in the air 7and by gas molecules as well7 is a deep blue and there exists no reason why that part of the light which is thrown outward into space should be of a different colour4 ,the ,earth1 therefore1 is blue in contradistinction to ,mars which is red1 on account of its desert surface1 and ,venus which is bright white4 ,the cloudy portions around the equator and the poles should appear light blue from without and should be separated by dark blue bands over the so-called horse latitudes1 under which the cloudless desert regions are located on either side of the equator4 7,compare the title page illustration47 ,compared to ,mars the ,moon offers a scene of far greater desolation4 ,on ,mars1 we observe at least some considerable changes such as the disappearance of the white pole-caps at midsummer when at the same time a dark ring appears to surround them2 then the 8lakes0 and the 8canals0 come into view1 beginning close to the ring mentioned1 later on nearer the equator1 and finally on its other side1 while the opposite pole-cap puts on its winter hue4 ,again1 we have the sudden appearance1 and equally hasty disappearance1 of white spots1 particularly in the neighbourhood of the lakes1 and the sand storms which hide the surface of ,mars and often fill its canals4 ,the abruptness of the changes indicate that they are confined to a very thin surface layer4 ,the formation1 on the other hand1 of canals1 for many years unobserved1 must be ascribed to a volcanic activity which1 while feeble1 yet must be seated in the deeper portions of the planet4 ,in addition1 a stunted vegetation of low forms is not unthinkable in the polar regions4 ,as against this1 the ,moon is undoubtedly a stellar body entirely insusceptible of surface change4 ,near its centre1 it is probably not completely solidified and an extremely slow growth of the firm crust is therefore likely4 ,gases are no doubt set free during this process1 but they are unable to penetrate the enclosing thick armour and remain therefore as bubbles in the hardening magma4 ,as a matter of fact1 no changes have1 with certainty1 been detected on the ,moon's surface4 ,it is true that the great ,wm4 ,herschel1 known as an excellent observer1 believed that he discovered1 in #ahgc1 mountains which had not existed before that time1 and ,schrter1 who diligently studied the lunar surface1 was of the opinion that he too had discerned numerous changes4 ,these discoveries1 however1 were doubted by careful critics1 and after the publication of ,mdler's great work about the ,moon 7#ahcg7 the complete stagnation on that body was taken for granted4 ,nevertheless1 there are several astronomers1 such as ,schmidt in ,athens 7#ahff7 and lately ,w4 ,h4 ,pickering in ,cambridge1 ,mass41 who think that they have discerned considerable modifications4 ,the former held that the crater ,linn 7,fig4 #bg7 had vanished since the publication of ,mdler's work4 ,in #ahfg1 ,mdler1 himself1 proclaimed that it had the same appearance as before4 ,pickering1 again1 reports periodic changes of 8snow0 and 8vegetation40 7,compare ,fig4 #bg taken from ,pickering's ,moon-atlas47 ,closer analysis1 however1 indicates that the phenomena are probably only apparent and depend on the angle of illumination at each particular time of observation4 ,for some time1 rather more than a quarter of a century1 photography has been pressed into the service of lunar investigation with far more objective results than would be possible through direct ocular inspection alone4 ,during this period1 which1 it must be admitted1 is not very long1 no distinct signs of changes have been recorded by the photographic plates4 ,the great difference between ,mars and the ,moon depends upon the existence of a real atmosphere on the former4 ,the oxygen will probably vanish from ,mars also1 being used up in the course of disintegration4 ,but nitrogen1 argon1 and the other permanent gases will always remain1 as will the water vapour from the bodies of water ever present1 particularly around the south pole4 ,it is true that this water vapour also will diminish with sinking temperature and when the latter finally has reached the freezing point of the salt solutions on ,mars1 the canals and the lakes will cease to thaw out or liquify under the vapour distilled over from the warm to the cold pole4 ,but sand storms and thin mist formations will always appear and cause colour changes on the desolate planet4 ,if we wish to picture to us the future fate of our ,earth when it gradually enters the reign of darkness and cold in consequence of the enfeebling of the ,sun1 we must seek our illustration on ,mars and not on the ,moon4 ,slowly are the oceans going to freeze1 finally down to their bottom1 the abundance of the rainfalls will diminish1 only light snow will now and then bring change to a surface evermore transformed into a sand desert as far as the continents reach4 ,rents in the rocky substrata of the latter will appear as dark lines1 caused by the gases rising from the interior4 ,when the temperature at the equator has fallen below the freezing point1 the polar regions will remain the only parts where a light covering of frost will melt in the height of the summer season and where the last feeble organisms will eke out their hard existence1 resorting to a prolonged winter's sleep of their seeds and spores4 ,finally1 the last remnant of life will also disappear and sandstorms alone1 save for the gasps of gas emanation from fissures in the rocky ground1 will bring relief to the monotonous desolation4 ,falling meteoric dust1 which now exists in original state only on the bottom of the oceans1 will gradually cover the entire surface of the ,earth with a mantle coloured brick-red through the influence of atmospheric oxygen4 ,when the oxygen itself is used up1 the meteoric dust will retain its original greyish-green hue and lend it to the funeral pall of the ,earth4 ,very different conditions obtain on our neighbour planet1 which is closer both to the ,sun and to ourselves1 the radiant ,venus1 an object of interested human attention already in ancient times4 ,the average temperature there is calculated to about #dg ,c4 7#aaf4f ,f47 assuming the sun constant to two calories per cubic centimeter 74#jfa cu4 in47 per minute4 ,the humidity is probably about six times the average of that on the ,earth1 or three times that in ,congo where the average temperature is #bf ,c4 7#gh4h ,f74 ,the atmosphere of ,venus holds about as much water vapour #e km4 7#c4a miles7 above the surface as does the atmosphere of the ,earth at the surface4 ,we must therefore conclude that everything on ,venus is dripping wet4 ,the rainstorms on the other hand do not necessarily bring greater precipitation than with us4 ,the cloud-formation is enormous and dense rainclouds travel as high up as #aj km4 7#f4b miles74 ,the heat from the ,sun does not attack the ground but the dense clouds1 causing a powerful external circulation of air which carries the vapour to higher strata where it condenses into new clouds4 ,thus1 an effective barrier is formed against horizontal air currents in the great expanses below4 ,at the surface of ,venus1 therefore1 there exists a complete absence of wind both vertically1 as the ,sun's radiation is absorbed by the ever present clouds above1 and horizontally due to friction4 ,disintegration takes place with enormous rapidity1 probably about eight times as fast as on the ,earth1 and the violent rains carry the products speedily downhill where they fill the valleys and the oceans in front of all river mouths4 ,a very great part of the surface of ,venus is no doubt covered with swamps1 corresponding to those on the ,earth in which the coal deposits were formed1 except that they are about #cj ,c4 7#ed ,f47 warmer4 ,no dust is lifted high into the air to lend it a distinct colour2 ,only the dazzling white reflex from the clouds reaches the outside space and gives the planet its remarkable1 brilliantly white1 lustre4 ,the powerful air currents in the highest strata of the atmosphere equalize the temperature difference between poles and equator almost completely so that a uniform climate exists all over the planet analogous to conditions on the ,earth during its hottest periods4 ,the temperature on ,venus is not so high as to prevent a luxuriant vegetation4 ,the constantly uniform climatic conditions which exist everywhere result in an entire absence of adaptation to changing exterior conditions4 ,only low forms of life are therefore represented1 mostly no doubt belonging to the vegetable kingdom2 and the organisms are nearly of the same kind all over the planet4 ,the vegetative processes are greatly accelerated by the high temperature4 ,therefore1 the lifetime of the organisms is probably short4 ,their dead bodies1 decaying rapidly1 if lying in the open air1 fill it with stifling gases2 if embedded in the slime carried down by the rivers1 they speedily turn into small lumps of coal1 which1 later1 under the pressure of new layers combined with high temperature1 become particles of graphite4 ,fossils proper are not formed as was also the case in the early periods of the ,earth4 ,the temperature at the poles of ,venus is probably somewhat lower1 perhaps about #aj ,c4 7#ah ,f47 than the average temperature on the planet4 ,the organisms there should have developed into higher forms than elsewhere1 and progress and culture1 if we may so express it1 will gradually spread from the poles toward the equator4 ,later1 the temperature will sink1 the dense clouds and the gloom disperse1 and some time1 perhaps not before life on the ,earth has reverted to its simpler forms or has even become extinct1 a flora and a fauna will appear1 similar in kind to those that now delight our human eye1 and ,venus will then indeed be the 8,heavenly ,queen0 of ,babylonian fame1 not because of her radiant lustre alone1 but as the dwelling place of the highest beings in our solar system4 ,the ancients believed that the fates of men could be read in the stars and this faith persisted with the power of a religion until a few centuries ago4 ,it was shared by the foremost astronomers1 pre-eminently by ,tycho ,brahe1 who endeavoured to support it through his investigations4 ,traces are yet to be found in popular conceptions4 ,these ideas have been verified today in a certain sense although with a wholly different meaning than held by our forefathers4 ,the planets do tell us the conditions that existed on the ,earth at the first dawn of life and we can also draw from them a prediction of the fate that once1 after milliards of years perhaps1 will befall the latter descendants of present generations4 ,in one respect the dreams of our ancestors have not proved true1 namely1 with reference to the habitability of the other globes in our solar system4 ,according to the great ,kant1 conditions on the wandering stars outside of the ,earth's orbit were so favourable to life that their inhabitants ought to have reached a far higher development than beings on the ,earth4 ,the last remnant of this conception lives in the speculations about the marvellously proficient engineers who built the magnificent system of giant canals on ,mars4 ,a thorough critique has demonstrated that any other planet in our solar system hardly can offer an abode for higher beings1 except this very ,earth1 which therefore justly may be called 8the best of worlds0 among those that we know4 ,and yet1 it was undoubtedly a great truth that ,giordano ,bruno gave his life for1 because it is highly probable1 nay almost certain1 that around the countless suns which dot the firmament spin dark bodies1 although unfortunately our most powerful lenses do not reveal them4 ,a number of these unseen stellar bodies shelter living beings1 which even might have climbed to a higher point on the ladder of evolution than have the inhabitants of the ,earth4 ,illustration3 ,fig4 #ag4 ,map of the planet ,mars in ,mercator's projection according to drawing by ,schiaparelli4 ,a comparison with the drawing by ,antoniadi 7,fig4 #ag;a7 suggests that ,schiaparelli has made a somewhat diagrammatic picture1 which sets forth a very great number of strictly straight 8canals40 ,illustration3 ,fig4 #ag;a4 ,map of the planet ,mars in ,mercator's projection1 drawn in #aiji by ,e4 ,m4 ,antoniadi4 ,explanations3 ,meredies south2 ,oriens east2 ,occidens west2 ,septentrio north2 ,nix snow4 ,abbreviations3 ,m ,mare1 sea2 ,s ,sinus1 bay2 ,fr ,fretum1 channel2 ,l ,lacus1 lake2 ,fl ,flumen1 river2 ,r ,regio1 region2 ,i ,insula1 island2 ,pr ,promontorium1 cape4 ,a ,selection from the ,catalogue of ,g4 ,p4 ,,putnam',s ,,sons ,complete ,catalogue sent on application ,the ,essence of ,astronomy ,things ,every ,one ,should ,know ,about the ,sun1 ,moon and ,stars ,by ,edward ,w4 ,price #abmo4 ,fully ,illustrated4 ,price #a4ej4 ,by mail1 #a4fe ,here is a volume quite different from the usual 8popular book on astronomy40 ,it answers in untechnical language the every-day questions of every-day people1 the material being so arranged that it is readily available for quick reference use1 as well as for interesting consecutive reading4 ,an individual chapter is devoted to each member of the ,solar ,system4 ,special space is given to 8,freaks and ,oddities of the ,skies40 ,the illustrations are from photographs taken at the great observatories4 ,the drawings of ,mars are the most recent published1 being made by ,professor ,lowell in ,january of this year4 ,the chronological table and annotated bibliography are of real value4 ,sun ,lore of ,all ,ages ,a ,collection of ,myths and ,legends ,concerning the ,sun and its ,worship ,by ,william ,tyler ,olcott ,author of 8,star ,lore of ,all ,ages10 8,a ,field ,book of the ,stars10 etc4 #ho4 ,with #cj ,illustrations4 #b4ej net4 ,by mail1 #b4gj ,a companion volume to ,star ,lore of ,all ,ages by the same author4 ,it comprises a compilation of the myths1 legends1 and facts concerning the sun1 of equal interest to the lay-reader or to the student4 ,the literature of the subject is teeming with interest1 linked as it is with the life story of mankind from the cradle of the race to the present day1 for the solar myth lies at the very foundation of all mythology1 and as such must forever claim pre-eminence4 ,g4 ,p4 ,putnam's ,sons ,new ,york ,london ,a ,beginner's ,star-,book ,an ,easy ,guide to the ,stars and to the ,astronomical ,uses of the ,opera-,glass1 the ,field-,glass1 and the ,telescope ,by ,kelvin ,mc,kready ,square #hvo4 ,including #gj ,illustrations4 #b4ge net4 ,postage ,additional ,this volume1 peculiarly definite and helpful in method1 is especially adapted to the practical needs of those who wish a well illustrated and clearly written handbook1--accurate in its scientific information and yet popular enough to meet the wishes of the average man or woman4 ,the book is distinguished from other volumes on popular astronomy by a novel system of mapping1 and by an unusually full discussion of the uses of the simpler astronomical instruments4 ,special care has been given to reproductions of recent astronomical photographs4 8,mr4 ,mc,kready's book is the finest thing for the beginner that ,i have ever seen4 ,it is a pleasure to read a book so excellent in so many different ways4 ,i have never seen photographs reproduced better4 ,i have never seen maps of the heavens so intelligible to the beginner1 and ,i have never read explanations so concise and yet so complete as in this book40--,prof4 ,s4 ,a4 ,mitchell1 ,department of ,astronomy1 ,columbia ,university1 ,new ,york ,city4 ,new ,york ,g4 ,p4 ,putnam's ,sons ,london ,a ,revised ,edition of a ,standard ,work ,a ,field ,book of the ,stars ,by ,william ,tyler ,olcott ,author of 8,star ,lore of ,all ,ages10 etc4 ,second ,edition1 ,revised4 ,with ,additional ,material4 #afo4 ,with ,fifty ,diagrams4 #a4jj net4 ,by mail1 #a4aj ,in the new edition of this standard work the author has given full information1 together with diagrams representing the result of the latest investigations4 ,all matters of a technical or theoretical nature have been omitted4 ,only what the reader can observe with the naked eye or with an opera-glass have been included in it4 ,excellently arranged and copiously illustrated1 this manual is a real field-book and will prove valuable for all who wish to become familiar with the stars4 ,new ,york ,g4 ,p4 ,putnam's ,sons ,london ,star ,lore of ,all ,ages ,a ,collection of ,myths1 ,legends1 and ,facts1 ,concerning the ,constellations of the ,northern ,hemisphere ,by ,william ,tyler ,olcott ,author of 8,a ,field ,book of the ,stars10 etc4 #ho4 ,with #afd ,illustrations and ,diagrams #c4ej net4 ,by mail1 #c4ge 8,a sumptuous treasure-house in which the lover of ancient myth and modern miracle may wander for enchanted hours4 ,its red and gold doors open upon a gallery of masterpieces in art1 all being inspired conceptions connected in some way with star lore4 ,the pictures and the legends of all ages have been ransacked to make this gallery irresistible to art and nature lovers1 and not in vain4 ,withal the most intense facts of astronomical knowledge and discovery are given beside the tapestried romance which earlier peoples wove with star-stuff as the medium of their art4 ,it is a book delightful to the eye1 scholarly in conception and treatment1 and charming to the inner sense40--,from ,scientific ,american4 8,here all the myths1 legends1 and facts relating to all our northern constellations are set forth fully as well as with scientific exactness1 are illustrated with clear maps and diagrams1 and are brought into close association with their classic origins by beautifully reproduced photographs of works of art and architecture40 ,the ,outlook4 ,new ,york ,g4 ,p4 ,putnam's ,sons ,london ,transcriber's ,notes ,punctuation and spelling were made consistent when a predominant preference was found in this book2 otherwise they were not changed4 ,simple typographical errors were corrected2 occasional unbalanced quotation marks retained4 ,the spelling and accent marks of non-,english words have not been changed4 ,ambiguous hyphens at the ends of lines were retained2 occurrences of inconsistent hyphenation have not been changed4 ,illustrations have been moved1 when necessary1 to fall between paragraphs and outside of quoted text4 ,in some cases1 this places them on different pages than the ones given in the ,table of ,illustrations4 ,in versions of this e,book that support 8links01 the page numbers in that table link to the correct illustrations4 ,wide tables on pages #aac and #adf have been split to fit within recommended width limits4 ,the left-hand identifier columns have been duplicated in both halves of the split tables4