950 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



inch pipe will convey about 5 J times as much water as an inch pipe; a 

 three-inch pipe nearly fifteen times as much. A one-inch pipe with an 

 inclination of one in 1,000 will convey water enough for hatching 25,000 

 eggs; with an inclination of one in fifty, enough for 100,000 eggs; with 

 an inclination of one in twenty, enough for nearly 200,000 eggs. A square 

 conduit will convey one-quarter more water than a cylindrical pipe of same 

 diameter. If there are any angles or abrupt bends in the pipe its capacity 

 will be considerably reduced. It should be remembered that if the water 

 completely fills the aqueduct it is thereby entirely shut out from contact with 

 air during its passage, whereas if the pipe be larger than the water can 'fill 

 the remainder of the space will be occupied by air, of which the water, 

 rushing down the incline, will absorb a considerable volume and be thereby 

 greatly improved. It will therefore be much better, when practicable, (and 

 this includes nearly all cases,) to make the conduit twice or thrice the 

 size demanded by the required volume of water. If the bottom and sides 

 be rough, so as to break up the water, so much the better; and the wider 

 the conduit is of course the more surface does the water present to the air. 

 It is not at all necessary to cover the conduit, unless from its position it is 

 exposed to inundation or to pollution by the visits of mischievous animals 

 or other agencies, or unless, as may sometimes, but rarely, occur, the water 

 would be in danger of freezing up. If the water comes from springs or a 

 spring brook, or a lake or pond, there is no danger on that side, unless the 

 aqueduct is a very long one ; on the contrary, the spring water will only 

 receive a wholesome cooling down. 



5.— AERATION. 



This is perhaps the most important branch of the whole subject. The 

 water which fishes breathe is but the medium for the conveyance of air, 

 which is the real vivifying agent. Without air every fish and every egg 

 must surely die, and with a scanty supply the proper development of the 

 growing embryo becomes impossible. Water readily absorbs air whenever 

 it comes in contact with it, and the more intimate and long continued the 

 contact the greater the volume it will absorb. The ample aeration of the 

 water to be used in the hatching-house has already been mentioned as a 

 desideratum of the first importance, and some of the devices by which it 

 is to be secured have been incidentally alluded to. But a little more 

 remains to be said. 



Water from either a brook or river that has been torn into froth by 

 dashing down a steep bed has absorbed all the air that will be needed in 

 ten or twenty feet of hatching-trough, and demands no farther attention on 

 this score. But if the water must be taken from a lake, a spring, or a 

 quiet brook, its burden of air is much less and is liable to become so reduced 

 before it gets through the hatching-house as to be unable to do its proper 



