Prof. Struder on Bowlders. 331 
We can avoid a part of these difficult questions, if we assume 
with HH. Acassiz and Scurimprer a general ice-covering of the 
earth, a freezing of the water in seas, lakes and streams from the 
poles to the equator. On the frozen inland sea, which thus in 
part overspread Switzerland, the Alpine fragments might have 
been slid to the Jura and to the slopes of the outjutting molasse 
hills, and in the same manner the Swedish blocks could have 
been shoved across the Baltic. 'The sudden occurrence of this 
ice-epoch was the cause of the destruction of the antediluvian 
animal races and vegetable species, of which not a single sort has 
survived to our time: and thus even in the earlier geological 
epochs, the periods of heat and life have been interrupted by pe- 
tiods of freezing and death. This originally Indian view of na- 
ture is capable of taking a very poetical form ; and Hr. Schimp- 
fer has given us a specimen of it. It looses, moreover, with the 
Sword of Alexander to be sure, several of the most ravelled knots 
in Geology and Paleontology, but to make it harmonize with 
facts and with the prose of physical investigations, is a problem 
Which far surpasses at least my powers —the striking relations 
between the dispersion of the blocks and the shape of the val- 
lies, which must ever lie at the foundation of any satisfactory 
theory, are left in the one lately proposed unregarded and unex- 
plained. We see not how the blocks could have alighted, as they 
often have done in great numbers, behind outjutting hills, or 
pressed in upon the sides of the vallies; why, farther, their zone 
Tises so high on the Jura opposite the Rhone-valley, and then to- 
wards Soleure gradually sinks down till it reaches the present 
valley-bottom ; wherefore in the narrows of the vallies, the blocks 
are altogether wanting, while on the contrary in the wide portions 
they occur in the greatest number. But still more difficult is it 
to see from whence this periodical freezing, this alternation of 
heat and cold, of life and death, could have been derived. Not 
from a change of internal heat, for we know from Fourier, that at 
Present, the influence of the internal heat upon the temperature 
of the surface scarcely amounts to ;'5° ¢. The warmth in which 
We live, and which remains constant at different depths of the 
ground according to latitude, and also agrees with the mean an- 
hual warmth of the atmosphere, is almost exclusively an effect of. 
the sun. We might accordingly be referred to a periodical change 
in the intensity of solar heat,—a problem, with which Herschel 
