OVIBOS MOSCHATUS. 27 



bound to admit to be the case throughout all past time, then the evidence of relative 

 levels is not decisive. What are now low-level deposits, may, in some cases, be of the 

 same antiquity as those at higher levels, owing to movements in the earth's crust since 

 they were deposited. Or again, if we suppose a valley with a river flowing through it, 

 to be depressed beneath the surface of the sea, the higher marine may yet be younger than 

 the lower fluviatile deposit, as in the case of the forest-bed on the Norfolk shore, on which 

 rest marine sands and gravels, and boulder clay, which have been deposited after its 

 submergence. Unless, therefore, in any particular case, there be no oscillations of level, 

 and unless there can be no interference by the sea with the cutting-down action of the 

 river, relative height is no standard of age. No proof of either of these conditions, neces- 

 sary to the truth of Mr. Prestwich's view, is to be found in the lower part of the Thames 

 Valley. On the contrary, since during the glacial epoch Scotland, 1 according to Sir Charles 

 Lyell, was depressed to a depth of two thousand feet beneath the sea, and the hills of 

 Wales to a still greater depth according to Professor Ramsay, 2 it seems to be incredible 

 that the Thames Valley should not have shared, in some degree, in this depression. 

 Whether or not the true boulder clay was ever deposited in the Thames Valley proper, is 

 an open question ; but the fact that it occupies the basin of the Roding, the affluent to 

 the Thames, as well as those of the two rivers immediately to the north, the Blackwater 

 and the Colne, proves that the main features of the country were sketched out before the 

 boulder clay age, and that it also was excavated in Preglacial times. It appears therefore 

 to me that, in this case, the evidence offered by the low-lying position of the strata is 

 valueless as compared with that offered by the mammalia in favour of the high antiquity. 

 Were the test of level to be applied to the forest-bed, it might be shown likewise to be of 

 late Pleistocene age, had it not been for the accident of the boulder clay being above. And 

 if this had been denuded away, we should merely have had the mammalia to show the true 

 geological age of the deposit in which they were found. 



§ 7. The Mange in Space and Time of Ovibos Moschatm. — We have now quoted all 

 the localities on record in which the remains of fossil Ovibos have been found. During 

 the Pleistocene age, it ranged over northern Siberia and the plains of Germany and 

 Prance, occurring very generally in the river deposits along with Reindeer, Mammoth, and 

 Woolly Rhinoceros. In England four out of five cases of its occurrence are in ordinary 

 Pleistocene gravels, while the fifth relegates it to a more ancient date, in which 

 Pleiocene mammalia lived, side by side, in the valley of the Thames, with those that are 

 characteristic of the Pleistocene period. That the animal was very rare in the Postglacial 

 deposits in Europe is proved by its having been found in only ten places. In Siberia, 

 although only three instances are on record of its having been found, it is probably abun- 



1 Lyell, ' Antiquity of Man.' 



2 Ramsay, 'Quart. Geol. Journ.,' 1851, p. 3/2. 



