966 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



this opinion he quotes the Arctic explorer, Franklin, to prove the 

 extraordinary vitality of fish under the influence of a much lower 

 temperature, in regions where the fish froze as they were taken 

 out of the nets, and in a short time became a solid mass of ice. 

 If in -this completely frozen state they were thawed before the 

 fire, they recovered their animation. The carp, for instance, Avould 

 thus recover so far as to leap about with much animation after 

 having been frozen for thirty-six hours. Heme, Ellis and others, 

 state that musketoes and other insects frozen into a black, solid 

 mass — spiders frozen so hard as to bound from the floor like a 

 pea — frozen leeches, frogs and snails, all recovered their energies 

 when thawed before the fire. These facts seem to prove that 

 although fishes may be made torpid by cold, and so not require 

 air, yet in their active state they must be supplied with this neces- 

 sary condition of life. The appetite for air is, no doubt, difi*erent 

 in different species. If carp and tench in an aquarium be v.'atched, 

 it will be found that the carp frequently seek the surface for air, 

 while the tench remain at the bottom. If various species be 

 crowded together in a tub of water, such as minnows, dace, roach, 

 o-udf>-eons, &c., some will die Ions; before the others for want of 

 air. Boccius, a practical manager and constructor of fish ponds, 

 distinctly recognizes the necessity of supplying air to the water 

 durino' frost. 



Experiments on the freezing of aerated waters show that when 

 they are frozen rapidly the air becomes entangled, and opaque, 

 milk-white ice is the result; but when the cold operates gradually, 

 clear crystalline ice is formed ; or if the air cannot escape, clear 

 ice is first formicd, and afterward the opaque aerated ice. A friend 

 has informed Mr. Tomlinson that a considerable number of small 

 blue roach had been killed in the ponds about Bromborough from 

 the sudden freezing of the ice. These ponds are very shallow, 

 and a sudden frost would entangle in the ice much of the air of 

 the water. On the other hand, if the cold increase gradually, the 

 water has time to separate the air, and no sooner is a crust formed 

 on the surface than this separation proceeds dov/nward, and often 

 with such eflfect as to collect the air in lenticular masses, which 

 appear of a light color amid the black ice. In this way the freez- 

 ing proceeds downward, and if the water be moderately deep, 

 the fishes not only enjoy a comparatively mild temperature, Init 

 have air enough until the frost breaks up, unless, indeed, it be of 

 unusual duration. 



