The extent of the tract through which these bones are scattered, is a circumstance truly wonderful. Pallas assures us,[226] that there is not a river of considerable size in all the north of Asia, from the Tanais, which runs into the Black Sea, to the Anadyr, which falls into the Gulf of Kamtchatka, in the sides or bottom of which bones of elephants and other large animals have not been found. This is especially the case where the rivers run in plains through gravel, sand, clay, &c.; among the mountains, the bones are rarely discovered. The extent of the tract just mentioned exceeds four thousand miles; and how the bones could be distributed over all that extent, by any means but by the animals having lived there, it seems impossible to conceive. No torrent nor inundation could have produced this effect, nor could the bones brought in that way have been laid together so as to form complete skeletons. [Footnote 226: De Reliquiis Animalium exoticorum, per Asiam Borealem repertis.--"Nov. Comment Petrop. tom. xvii. (1772,) p. 576.] 416. One fact recorded by the same author, seems calculated to remove all uncertainty. It is that of the carcase of a rhinoceros, almost entire, and covered with the hide, found in the earth in the banks of the river Wilui, which falls into the Lena below Jakutsk.[227] Some of the muscles and tendons were actually adhering to the head when Pallas received it. The head, after being dried in an oven, is still preserved in the museum at Petersburgh. The preservation of the skin and muscles of this natural mummy, as Pallas calls it, was no doubt brought about by its being buried in earth that was in a state of perpetual congelation; for the place is in the parallel of 64°, where the ground is never thawed but to a very small depth below the surface. [Footnote 227: Pallas _ubi supra_, p. 586. Also, Voyages de Pallas, tom. iv. p. 131.]