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POPULAR SCIENCE REVIEW. 
ference of inhabitants was far greater than lately ; bnt the con- 
ditions of existence changed but slowly during its continuance. 
Judging from the present position of the entrances of many 
of the principal bone-caverns, there must have been a consider- 
able elevation of extensive tracts in Europe since or during the 
period we refer to. Such an elevation must have tended to 
increase the quantity of land in the northern hemisphere, and 
in this way to modify and render less equable the climate of the 
temperate latitudes. As by degrees the change established 
itself, and large tracts of low flat land — the great plains of 
Germany — rose above the waves, and became clothed with 
forest, — the higher lands meanwhile becoming hills and moun- 
tains — one can readily imagine that the conditions favourable 
for these monsters may have altered; that different races, 
smaller but more active, took then' place; and that, by the 
time the change had been completed, the elevation should have 
carried out of reach the former habitations. Certainly there 
are few cases known in which caverns near the present level, 
either of the sea or of the adjacent valleys, have been found to 
bear marks of the habitation of ancient tribes of carnivora. 
In the south of Europe, and in somewhat earlier deposits 
also in the north, at least as far as Britain, there are very 
numerous remains of hippopotami, and in India the number of 
extinct species of this singular animal is wonderfully large. At 
the time when so aquatic a tribe, and one believed to require 
so high a temperature, could live in England and Northern 
Europe, there must at any rate have been a very different con- 
dition of things from that since prevailing*. 
South America also has its bone-caverns, and these are 
neither few in number, nor doubtful in their indications. What 
the various marsupials are to Australia, the equally special and 
well-marked edentates are to Brazil, and other parts of the vast 
tract of country between the Andes and the east coast of 
South America The sloth, the armadillo, and the ant-eater, 
are the characteristic animals. In the caverns and in the 
mud-banks, where there is no limestone at hand to be pene- 
trated and eaten away into holes, we find the ancient repre- 
sentative of these modern tribes. The difference here, however, 
is even more marvellous in extent than either in Europe or 
Australia, though similar in kind. In the place of the sloth, 
we have giants as remarkable for their massive proportions as 
for their size, though in that they exceed the elephant. Instead 
of the armadillo, there is a creature whose cuirass is not only 
larger, but harder and tougher than that of any living animal 
supplied with such defence. So also the ruminating animals 
are represented in similar proportion; and all point to con- 
