OF THE CHANGES OF CLIMATE. 
355 
out the space occupied by Europe, of a transition 
from the condition of an ocean, interspersed with 
islands, to tiuit of a large continent ; and to this 
increase of the land in the northern hemisphere 
we may jirobably attribute, in a great measure, 
that gradual diminution of temjierature which the 
organic remains of the different periods denote. 
“ The climate was hottest when the northern he- 
misphere was for the most part occujiied by the 
ocean ; and the refrigeration did not become con- 
siderable until a very large proportion of that ocean 
was converted into land, and rejilaced in some 
parts by high mountain chains : nor did the cold 
reach its maximum until these chains attained 
their gi'eatest elevation, and the land its utmost 
extension.”* 
* Lyell’s Principles of Geology, vol. i. chap. vii. The remarks of 
one of our most eminent astronomers on this beautiful tlieory of Mr. 
Lyell are so pertinent, that I cannot omit them. “ The fact of a great 
change in the general climate of large tracts of the globe, if not of the 
whole earth, and of a diminution of general temperature, having been 
recognised by geologists, from their examination of the remains of 
animals and vegetables of former ages enclosed in the strata, various 
causes for such diminution of temperature have been assigned.” After 
observing on the theories which attempt to explain the present decrease 
of temperature, by supposing that the whole globe has gradually cooled 
from a state of absolute fusion; and that, in former ages, there was an 
immensely superior activity in volcanic action. Sir John Herschel 
proceeds to remark : — “ Neither of these can be regarded as real causes 
in the sense here intended; for we do not know that the globe has so 
cooleil from fusion, 7ior are we sure that such supposed superior activity 
of former than of present volcanoes really did exist. A cause, pos- 
sessing the essential requisites of a vera causa, has, however, been 
brought forward by Mr. Lyell, in the varying influence of the dis- 
tribution of land and sea over the surface of the globe : a change of 
such distribution, in the lapse of ages, by the degradation of the old con- 
tinents, and the elevation of new, being a demonstrated fact ; and the 
influence of such a change on the climates of particular regions, if not 
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