1092 THE MICROSCOPE IN GEOLOGICAL INVESTIGATION 



The researches of Professor Quekett on the minute structure of 

 bone l have shown that from the average size and form of the lacunae, 

 their disposition in regard to each other and to the Haversian 

 canals, and the number and course of the canaliculi, the nature of 

 even a minute fragment of bone may often be determined with a 

 considerable approach to certainty, as in the following examples, 

 among many which might be cited : Dr. Falconer, the distinguished 

 investigator of the fossil remains of the Himalayan region, and the 

 discoverer of the gigantic fossil tortoise of the Sivalik hills, having 

 met with certain small bones about which he was doubtful, placed 

 them for minute examination in the hands of Professor Quekett. 

 who informed him, on microscopic evidence, that they might certainly 

 be pronounced reptilian, and probably belonged to an animal of the 

 tortoise tribe ; and this determination was fully borne out by other 

 evidence, which led Dr. Falconer to conclude that they were toe- 



/ 



bones of his great tortoise. Some fragments of bone were found. 

 many years since, in a chalk-pit, which were considered by Professor 

 Owen to have formed part of the wing-bones of a long-winged sea 

 bird allied to the albatross. This determination, founded solely 011 

 considerations derived from the very imperfectly preserved external 

 forms of these fragments, was called in question by some other 

 palaeontologists, who thought it more probable that these bone-; 

 belonged to a large species of the extinct genus Pterodactylws, a flying 

 lizard whose wing was extended upon a single immensely prolonged 

 digit. No species of pterodactyle, however, at all comparable to 

 this in dimensions, Avas at that time known ; and the characters 

 furnished by the configuration of the bones not being in any degree 

 decisive, the question would have long remained unsettled had not 

 an appeal been made to the microscopic- test. This appeal was so 

 decisive, by showing that the minute structure of the bone in ques- 

 tion corresponded exactly with that of pterodactyle bone, and. differed 

 essentially from that of every known bird, that no one Avho placed 

 much reliance upon that evidence could entertain the slightest doubt 

 on the matter. By Professor Owen, however, the validity of that 

 determination was questioned, and the bone was still maintained to 

 be that of a bird, until the question Avas finally set at rest, and the 

 value of the microscopic test triumphantly confirmed, by the discovery 

 of undoubted pterodactyle bones of corresponding and even of greater 

 dimensions in the same and other chalk quarries. 



The microscopic examination of the sediments no\\ in course of 

 deposition on various parts of the great oceanic area, and especially 

 of the large number of samples brought up in the ' Challenger 'sound- 

 ings, has led to this very remarkable conclusion that the detritus 

 resulting from the degradation of continental land-masses is not 

 carried far from their shores, being entirely absent from the bottom 

 of the ocean-basins. The sediments there found were not of 

 organic origin, hut mainly consist of volcanic i/Ma-ix and of clay that 

 seems 1o have been produced by the disintegration of masses of very 



See ins iiiciiiciir (Hi the ' Comparative SI nictmv nt I'.mie ' in the Trans. Microsc. 

 er. i. \ol. ii.; and the ('<itti/n(/in- uft/n- Ilinfii/uf/ii-ii/ Miixritiii uf fhr R<>>/. Coll. 



i,i' Surgeons, >1. ii. 



