Investigations and Writings of Baron Humboldt. 211 
But another consideration comes here to be taken into ac- 
count. When Humboldt elucidated the above view, he as- 
sumed the fundamental principles of Werner, that all the older 
erystalline rocks, such as granite, had been likewise produced 
by deposition from water ; but we now know that these could 
not have been formed by the action of water, and we have thus 
to separate such substances from the series. As, however, these 
rocks have been produced by voleanic action, although we lose 
them asa support of the theory by precipitation, there is opened 
to us another and more powerful source of heat, arising from the 
eruption of large masses of burning matter, and from the dis- 
engagement of their accompanying hot yapours. These phe- 
nomena have, at different periods of the history of the earth, 
included at one and the same time a space of many thousand 
Square miles ; and hence, in recent times, it has become a pro- 
bable opinion that the uniformly elevated temperature of the 
ancient world is to be ascribed to the much more vigorous 
activity of volcanic agency; nay, even Humboldt himself has 
been one of the first to express openly this belief, and to argue 
in its favour. In the year 1823 he treats of this view in an 
extremely beautiful memoir on the structure and mode of 
action of volcanos. 
This last opinion as to the causes of the higher temperature 
which prevailed over the ancient surface of our globe, ap- 
proaches the remarkable hypothesis of Buffon; and it cannot 
be denied that it is much more capable of explaining the phe- 
nomena in question. Nevertheless, there is one fact which 
has hitherto defied all attempts to include it in this solu- 
tion of the problem. After the heat and the general character 
of the tropical climate had existed for an unlimited period, 
over a large portion of the earth’s surface, it must have ter- 
minated by some suddenly occurring event. It is well known 
that the elephants, buffalos, and rhinoceroses which at one pe- 
riod inhabited Siberia, and some quarters of North America, 
and especially the banks of the Wilui and Lena, were, with 
their soft parts, enveloped by the ice in which they are now 
found. Hence, at a certain time, when they were living in 
full vigour and tranquillity, they must have been surprised by 
the inconceivably sudden occurrence of a cold approaching 
