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103 
the water, on which it swims with about half its body sub- 
merged. Now it has need to guard against enemies from 
above and below : eyes which would see well in the air, 
would not see well in the water, on account of the difference 
in the density of these media, and besides, one pair of eyes 
could not be in both the air and water at once. To obviate 
this inconvenience, the Gyrinus has one pair just above the 
surface, and another pair just below, very close together, yet 
sufficiently separate to be in different elements. Insect 
anatomists find that the two eyes, that is, the upper and 
lower eye on each side, are joined internally, and connected 
with one optic nerve, — an example of economy of materials 
by no means uncommon. 
C. — Going down to Spafford's bridge yesterday, I ob- 
served that the river had overflowed its banks, and inun- 
dated the extensive meadows and low lands on each side, 
so that it looked like a large lake : the road was impassable 
for foot passengers. 
F. — These freshets, as they are termed, occur every springs 
and are caused by the melting of the accumulated snows of 
the past winter. It is true our snow has disappeared some 
time, and the roads are comparatively dry, but it is in the 
mountains that these freshets originate. The snow there 
does not melt so soon as in less elevated regions ; and as all 
the springs and rivers have their sources among the hills, 
they are comparatively little affected, until the melting of 
the mountain snows. — On such of our rivers as have steep 
banks, as the St. Maurice and the Magog, I am informed it 
is not uncommon for dides to occur at this season. Heavy 
spring rains undermine the earth, while yet frozen, and loosen 
it from the subsoil, when large portions of the surface, with 
all their trees and bushes, slide off the rock beneath, and 
