4i8 



NATURE 



\jAugust 15, 1878 



the earth, amounting to six thousand three hundred and seventy- 

 eight feet, ^ such a fact \vould appear to point to a great want 

 of homogeneity in the interior of our planet, and might suggest 

 a possible cause for some disturbance of equilibrium. 



I have mentioned Prof. Haughton among those who, from 

 mathematical considerations, have arrived at the conclusion 

 that a geographical change in the position of the axis of rota- 

 tion of the earth is not only possible but probable. In a recent 

 paper, however, he has maintained that notwithstanding this 

 possibility or probability, we can demonstrate that the pole has 

 not sensibly changed its position during geological periods. He 

 arrives at this conclusion by pointing out that in the Parry 

 Islands, Alaska and Spitzbergen, there are triassic and Jurassic 

 deposits of much the same tropical character, and then by a 

 geometrical method fixing the north pole somewhere near 

 Pekin, and the south pole in Patagonia, within seven hundred 

 miles of a spot where Jurassic ammonites occur, shows that 

 such a theory is untenable. In the same way he fixes the pole 

 in miocene times near Yakutsk, within eight hundred miles of 

 certain miocene coal-beds of the Japanese islands. These ob- 

 jections are at first sight startling, but I think it will be found 

 that if, instead of drawing great circles through certain points, 

 we regard those points as merely isolated localities in a belt of 

 considerable width, there is no need of fixing the pole of either 

 the Jurassic or the miocene period with that amount of nicety 

 with which Prof. Haughton has ascertained its position. The 

 belt may indeed be made to contain the very places on which 

 the objection is founded. Still the method proposed is a 

 good one, and I hope that as our knowledge of foreign geology 

 extends it may be still further pursued. There is, however, one 

 farther consideration to be urged, and that is as to the safety of 

 regarding all deposits of one geological period as contempora- 

 neous in time. Although an almost identical flora may be dis- 

 covered in two widely -separated beds, it appears to me that 

 chronologically they are more probably of different ages than 

 absolutely contemporaneous ; and, inasmuch as the duration of 

 the miocene period must have been enormous, there would be 

 time — if once we assume the wandering of the poles — for such 

 wandering to have been considerable between the beginning and 

 end of the period. 



I must not, however, detain you longer upon this phase of 

 geological speculation, but will advert to a subject of more 

 practical interest, the discovery of palaeozoic rocks under 

 London, So long ago as 1856 the Kentish Town boring had 

 shown that immediately below the gault red and variegated 

 sandstones and clays occurred, which Professor Prestwich re- 

 garded as probably of old red or Devonian age. The boring 

 of Messrs. Meux & Co. has now shown that under Tottenham 

 Court Road, at a depth of little more than nine hundred feet 

 from the surface, there are true Devonian beds, with charac- 

 teristic fossils, and that Mr. Godwin Austen's prophecy of the 

 existence of palaeozoic rocks at an accessible depth under London 

 has proved true. Prof. Prestwich, from a consideration of the 

 French and Belgian coal-fields, inclines to the belief that in the 

 district north of London carboniferous strata may be found. 

 Unfortunately the expense of conducting deep borings, even 

 with the admirable appliances of the Diamond Boring Company, 

 is so great that I almost despair of another experimental borehole, 

 like that carried out in the Wealden district under the auspices 

 of Mr. Willett, being undertaken. 



In the department of theoretical geology I would call your 

 attention to some experiments by M. Daubree, of which he has 

 given accounts at different times to the French Academy of 

 Sciences. In these experiments he has attempted to reproduce 

 on a small scale various geological phenomena, such as faulting, 

 deavage, jointing, and the elevation of mountain chains. 

 Although the analogy between work in the laboratory and that 

 on the grand scale of nature may not in all cases be perfect, yet 

 these experiments are in the highest degree instructive, and 

 reflect no little credit on the ingenuity of the distinguished 

 chief of the Ecole des Mines. 



With regard to recent progress in palaeontology, I must ven- 

 ture to refer you to Prof. AUeyne Nicholson's inaugural address 

 lately delivered to the Edinburgh Geological Society, but I 

 cannot pass over in silence the magnificent discoveries in North 

 America, which are principally due to the researches of Profs. 

 Marsh, Leidy, and Cope. The Diceratherium, a rhinoceros 

 with two horns placed transversely, and the Di7ioce}-asy%,ovs\&wi)x%t 

 allied to the elephant, but with six horns, arranged in pairs, are 

 ' Thomson and Tait, "Phil." p. 648. 



as marvellous as some of the beasts seen by Sir John Maun- 

 deville on his travels, or heard of by Pliny. But perhaps the 

 most remarkable series of remains ever discovered are those 

 which so completely link the existing horse with the Eohippus 

 and Orohippus, and still farther extend the pedigree of the genus 

 Equus, which had already been some years ago so ably traced by 

 Prof. Huxley. 



Of these American discoveries, as well as those made in the 

 tertiary beds of Europe, M. Albert Gaudry has largely availed 

 himself in his recent beautiful volume on the links in the animal 

 world in geological times, a work which will long be a text-book 

 on the inter-relation of different orders, genera, and species. I 

 am tempted to make use of some portions of M. Gaudry's own 

 analysis of the book, which he communicated to the Geological 

 Society of France. Beginning with the marsupials of the close 

 of the secondary and beginning of the tertiary period, he shows 

 that they are succeeded by such animals as the Pterodon, the HycE- 

 nodon, the Proviverra, and Arctocyon, which present a mixture of 

 marsupial and placental characters, and to some extent justify a 

 theory of the transition from one order to the other. He next 

 examines the marine mammalia, and points out that, so far as at 

 present known, they make their appearance later tian those of 

 the land, and that the examination of the pelvis of the Halithe- 

 Hum tends to support the idea that the mammals, such as the 

 sirenians, which at the present day have no hind limbs, are 

 descended from terrestrial quadrupeds, for those limbs in the 

 Halilherium are much less reduced than in its recent successors, 

 the dugong and manatee. After tracing the numerous links 

 which are to be found between the extinct and living pachyder- 

 mata, he proceeds to shoAV that, notwithstanding the great dis- 

 tance between them and the ruminants, transitions may be seen. 

 The earliest ruminants were devoid of horns and antlers, but 

 possessed upper incisors, and by a comparison of the molars of 

 different genera it may readily be conceived how the large bosses 

 of the omnivorous teeth of the pachyderms gradually shaded 

 into the small crescents of the teeth of the ruminants. At the 

 same time the passage from the heavy and complicated extremi- 

 ties of the limbs of the pachyderms to the simpler and lighter 

 feet of the ruminants can be traced. The history of the horse 

 family is also discussed, and the descent of existing probosci- 

 dians from the mastodonts is shown to be probable, though the 

 previous forms from which the mastodonts and dinotheria are de- 

 rived are as yet unknown. Nor can the origin of the carnivora as 

 yet be suggested, though passages between the six existing 

 families of the order may be observed. In conclusion M. 

 Gaudry devotes a chapter to the quadrumana, and thinks that 

 palaeontological observations tend to diminish the isolation 

 in which these mammals now stand with regard to the other 

 orders. 



One of the most important features insisted on by M. Gaudry 

 is that to which I have already alluded — the development of the 

 complicated molars of most mammals. His view is that by a 

 comparison with early and with foetal forms the probability may 

 be shown of these compound teeth being made up of what in 

 earlier forms were simple teeth — or, as he has termed them, 

 denticules — which have coalesced in the same manner as have 

 some other parts of the normal bony skeleton. In the compound 

 teeth the denticules in some cases preserve their original conical 

 form, as in the pig tribe ; in others are elongated transversely, 

 so as by their junction to form ridges, as in the tapirs ; while in 

 others, again, they are drawn out into longitudinal crescents, as 

 in the ruminants. Between these forms there are, of course, 

 innumerable transitions. They do not, however, appear to me 

 to affect the importance of M. Gaudry's observations, which 

 must be regarded as of the highest value in all attempts to trace 

 the inter-relation of different forms of mammalian life. I must 

 not, however, detain you longer on this subject, as I trust that 

 I have said enough to show the importance and interest of this 

 book. 



The discoveries of early forms of birds with teeth do not 

 come within M. Gaudry's province ; but Prof. Marsh has largely 

 added to our knowledge of these remarkable forms. The X^x- 

 \\z.ry Odontopteryx toliapicus from Sheppey, described by Prof . 

 Owen, seems rather to be endowed with bony tooth-like pro- 

 cesses in the jaw than actual teeth, and the head of the Argil- 

 lornis from the same locality is at present unknown. But the 

 Hesperornis and Ichthyornis from the cretaceous beds of America 

 possess veritable teeth, in the one case set in a long groove m 

 the jaw, and in the other in actual sockets. Such intermediate, 

 or, as Prof. Huxley would term them, intercalary, forms, tend 



