38 THE COMMERCIAL SEA FISHES OF 



if deposited, and thus affect the next year's supply. Irre- 

 spective of the horizontal circulation in the ocean, due to 

 the action of winds and storms, there is likewise a vertical 

 one, due to the polar cold. Chiefly from the Antarctic 

 area there is an underflow of polar water, which passes 

 towards the equatorial zone ; while a complimentary over- 

 flow proceeds from the equator towards the pole. 



Fish will recover, after having been apparently frozen, 

 as observed by Sir J. Franklin in his ' Voyage to the Polar 

 Seas/ when they appeared to be a solid mass of ice, and 

 lived after having been thawed. The same phenomenon 

 has been repeatedly observed in this country during the 

 winter ; but M. Pouchet has demonstrated that no animal 

 really frozen is susceptible of revivication, as freezing dis- 

 organizes the blood. Animals may be surrounded by 

 ice without being frozen, unless the temperature is very 

 low. 



Fish can exist below the ice for lengthened periods, and 

 Arctic travellers have remarked that if a hole is broken 

 they congregate to that place ; but this may be due to an 

 increased amount of light, not for the purpose of breathing, 

 although when they thus congregate at one spot they 

 would probably foul the water. 



In an experiment made by M. Faure, he did not find 

 that fish in an aquarium took the slightest notice of the 

 electric light. It is well known that salmon and other fish 

 in fresh water are attracted by a light. The effects, how- 

 ever, of electrical disturbance in the atmosphere are fre- 

 quently perceived among the finny tribes, but more 

 commonly in fresh than in salt water. 



During the last few centuries, and the first decade of 

 the present, the theory was almost universally held that 

 gregarious sea fishes, as the mackerel and herring, had 



