April 24, 1884] 



NA'J'URE 



6c9 



account, and the iocl>s composing them were carefully examined, 

 !t was found that the explanations offered by the eminent French 

 geolcgi^t could not be adopted. 



Many valuable publications have been issued upon these sub- 

 jects, of which those of Robert Mallet may in many respects 

 claim our greatest atteniion. Another work of great value is 

 that of Prof. E. Sucss, the eminent Trofessor of Geology in the 

 University of Vienna, " Die Entslehung der Alpen," the forma- 

 tion of the Alps, in which this difficult question is treated in a 

 masterly manner. Prof. Green's " Physical Geology " contains 

 also an exhau.'live /Vo«///i? of the physics of the tarth's crust, in 

 which all the newest researches and theories are thoroughly 

 examined and sifted by an excellent obseiTcr and practical 

 ^eologit. However, there is another distinguished geologist 

 and physicist. Constant Prevost, whom I should not omit to 

 mention, he having rlready explained, in 1S22, the elevation of 

 mountain chains by tangential and lateral pressure, now mostly 

 adoiiled as the correct theory. The deep sea dredgings have 

 al o cftered us considerable material to elucidate the former 

 history of our globe, both from a stratigraphical and palasonto- 

 logical point of view. 



The oscillation of land and sea is another subject of great im- 

 portance that has hardly received that attention it de-erves, 

 whether we take the so-called glacial period into account or not. 

 There may be v\ ith many geologists the fear of appearing hetero- 

 dox if they state their belief that the hydrosphere is, like the 

 liihosphere, subjected to considerable oscillations, by which great 

 changes in the climate of the globe may have been broi;ght 

 about in past geological ages. For years I have held and stated 

 this opinion, 



IJowever, I find that lately a great deal of attention has been 

 paid to this subject. Thus, for instance, Ph. Fi-xher, Heinrich 

 Bruns, and others, in discussing pendulum observations, have 

 come to the conclusion that the sca level is not a regular 

 s]>Iicroid, but n";ay vary many hundreds of feet even along the 

 same parallel of latitude. Dr. Penck will also explain raised 

 beaches and other sijjns of the glacial period by the oscillation 

 of the sea-It vel. Penck's views in this respect are diflferent from 

 tho-^e of Adhemar and CroU. 



Another factor for explaining great changes on the earth's sur- 

 face, brought about in geological periods long past, has lately 

 been put forward under the name of Tidal Evolution, a very in- 

 geriious theory, first workeel out in its entirety by G. H. Darwin. 

 It is based upon the action of the moon, once a part of our 

 planet, on the earth, producing the tides and retarding its 

 motion, as well as upon the reaction of the earth upon its satel- 

 lite. Gradually the moon was driven away from our planet, 

 and the length of day has thus at the same rate become more 

 considerable. 



However, when Prof. Robert Ball, in Dublin, and others 

 attempt to make out that the former much larger tides, when 

 the moon was closer to the earth, formed a powerful agent for 

 the destruction of rocks existing at that time, and for the 

 formation of newer beds fiom them, by which the thickness 

 of the older sedimentary and fossiliferous strata can be ex- 

 plained, I think we have to pause before we can accept such 

 a sequence. 



Moreover, according to Sir William Thomson, there has not 

 been any great change in the ellipticity of the earth's figure 

 since its consolidation, consequently Mr. Darwin's views as to 

 higher tides have to be modified, as he presupposes a more 

 considerable ellip'icity for his calculations. However, even 

 assuming Prof. Ball's calculation, that when the moon was only 

 40,coo miles distant from the earth the tides at that time 

 would ri-eand fall between 600 and 700 feet twice in twenty-four 

 hours, to be correct, I have no doubt that it was long before the 

 Cambrian or lowest fossiliferous rocks with which we are ac- 

 quainted were deposited. The occurrence of numerous fossils 

 in the oldest beds, belonging to animals that could live only in 

 clear water, and minute ripple marks on the rocks, speak clearly 

 against Prof. Ball's hypothesis. 



This speculation in physical geography has already heen tested 

 by various geologists to account for the so-called marine denuda- 

 tion. This expression was first introduced by Sir Andrew Ram-ay 

 for the higher portions of ridges over large areas, that, if laid 

 down on an imaginary plane, appear to have once formed one 

 surface with a very gradual slope in one direction. 



However, this peculiar appearance can, as I have repeatedly 

 suggested in former publications, be easily explained by the fact 

 that when the land gradually rose above the sea-level, abrasion 



on a gigantic scale must have taken place, by which, in the case 

 of our Southern Alps, the whole had the appearance of a shal- 

 low dome, of which the western side was much steeper than the 

 eastern, till the subaerial erosion by atmospheric agencies, or, 

 as I called it, ridge making, took place. 



Before leaving this subject, to which I have devoted more 

 time than perhaps I ought to have done, I may add that many 

 speculations have heen built upon it. Thus, Mr. O. Fisher 

 attempts to prove that the ocean basin represents the scar w hence 

 the mass forming the moon separated from the earth. 



Another cause of gradual retardation in the rotation of our 

 planet, and to which, as far as I am aware, very little attention 

 has hitherto been paid, is the increase of the bulk of om- planet 

 by meteorites and cosmic dust. 



There is not the least doubt in my n.ind that matter, even in 

 the most diflused state, cannot leave the outermost or gaseous 

 portion of our plane', but that an enormous amount of matter 

 in the form of meteoi ites must have been accumulated year by 

 year. If we aeid to this the cosmic du-t falling upon the surface 

 of the earth, which, according to a calculation by Nordenskjold, 

 may amount to half a million tons yearly, the size of our planet 

 must have been gaining in dimensions and weight to an almost 

 inconceivable degree, even since a rich and diversified flora and 

 fauna inhabited it. But even assuming that Nordenskjbld's 

 estimate is far too high, and reducing it to a tenth, or to 5o,oco 

 tons yearly, the result of any calculation upon this basis is most 

 astounding. Thus, if we take only a period of twenty millions 

 of years, a short interval in the life-history of our planet, the 

 cotmic dust falling during that time would add not less than 

 1,0^0,000,000,000 or one billion of tons'. 



And this result is obtained without accounting in anyway 

 for the further addition by the fall of meteorites, without doubt 

 of very considerable magnitude. Such a factor, as Prcjf. von 

 Nordenskjold forcibly points out in his last work, ought certainly 

 not to lie overlooked if we wish to account for various changes 

 in the form, position, and rate of rotation of our planet since it 

 began to consolielate. 



I am well aware that several scientific men, who have care- 

 fully examined some of the cosmic dust, have come to the 

 conclusion that it is in most cases of terrestrial origin ; but the 

 fact remains that some of the dust collected shows its cosmic 

 origin by its constituent parts, and that all the meteorites reach 

 us from far beyonel the atmosphere of our earth. 



The importance of the great doctrine of evolution as first 

 fully established by Darwin cannot be overestimated by the 

 palasoutolcgist. Applying the leading facts of the origin and 

 distribution of animal and vegetable life, as at present existing, 

 to the numberless past generations preserved in the marvellous 

 stone-book of Nature, he is able to unravel more fully their 

 history, to account for the missing leaves, and to estimate at 

 their just value those few remaining, and of which he now and 

 then is privileged to decipher a small portion. Darwin himself, 

 in his classical chapter " On the imperfection of the geological 

 record," in his "Origin of Specie^," has pointed out to us in his 

 usual masterly manner how to avail ourselves of the scant mate- 

 rial at our command, and how future discoveries, adding to the 

 palaeontological stock, will open out new vistas in the past history 

 of our globe. 



I need scarcely add that every new addition to our knowledge 

 will assist us to gain more fully day by day an insight into the 

 harmonious unity of the whole. 



It is not yet a quarter of a century (1859) since the " Origin 

 of Species " appeared, but if we compare our knowledge of 

 palaeontology at that time with that obtained at present, we find 

 that striking progress has been made. Instead of a collection 

 of facts, more or less loosely connected, we now possess a 

 system of remarkable strength and harmony, a powerful aid to 

 an inductive science like geology. 



Evolution might be compared to an architect, who succeeds 

 in raising an edifice of pure and nolile proportions, placed upon 

 a stable .and firm fourdation, from a large accumulated material 

 of finely and ingeniously wrought building stones stored up 

 promiscuously without any apparent plan er order. 



Since the appearance of the "Origin of Species" I have 

 always held this opinion ; and I may be allowed to mention that 

 as far back as 1862, in my opening address as first president of 

 the Philosophical Institute, I spoke of this incomparable book 

 as " the great work of the age." 



The researches of the palaeontologist have shown already 

 convincingly that there are innumerable intermediate links 



