CHE-AP FIXTURES FOR THE HATCHING OF SALMON. 949 



cold. When spring water is used there is rarely any trouble, even in a 

 cool house, from the formation of ice in the troughs; but lake, river, or 

 brook water is, in the latitude of the northern tier of States, so cold in 

 winter that if the air of the hatching-house is allowed to remain much 

 below the freezing point, ice will form in the troughs and on the floor, if 

 there is any leakage, to such an extent as to be a serious annoyance, and 

 sometimes, if not watched, will form in the hatching-troughs and extend 

 so deep as to freeze the eggs and destroy them. Stoves are needed in such 

 climates to warm the air enough for the comfort of the attendants ; but 

 the house should be so warmly located and constructed that it may be left 

 without a fire for weeks without any dangerous accumulation of ice. The 

 easiest way to effect this is to have the house partly under ground; but if 

 the site does not permit this, the same result can be brought about by 

 thorough construction of the walls and by banking well with earth, saw- 

 dust, or other material. In warmer climates no trouble will be experi- 

 enced from this source. 



4.— DAMS AND CONDUITS. 



In some cases the best way to get the requisite head is to throw a dam 

 across the stream and locate the hatching-house close to it. The dam will 

 form a small pond which will serve the triple purpose of cooling, aerating, 

 and cleansing the water. But unless the character of the bed and banks 

 of the stream be such as to warrant against undermining or washing out at 

 the ends of the dam, it is best not to undertake to raise a great head in this 

 way. With any bottom except one of solid ledge there is always great 

 danger, and to guard against it when the dam is more than two feet high 

 may be very troublesome. If there is any scarcity of water, or if it be de- 

 sirable for any other reason, for aerating or other purposes, to secure a con- 

 siderable fall, it is better to construct the dam at some distance above the 

 hatching-house, on higher ground, where a very low dam will suffice to 

 turn the water into a conduit which will lead it into the hatching-house at 

 the desired height. 



The conduit is best made of wood. A square one of boards or planks, 

 carefully jointed and nailed, is in nearly all cases perfectly satisfactory. 

 For an ordinary establishment a very small conduit will suffice. The vol- 

 ume of water that will flow through a pipe of given form depends first, 

 upon the the size of the pipe, and second, upon the inclination at which it 

 is laid. A straight cylindrical pipe, one inch in diameter, inclined one foot 

 in ten, will convey about eleven gallons of water per minute. The same 

 pipe, with an inclination of one in twenty, will convey eight gallons per 

 minute; with an inclination of one in fifty, five gallons per minute; with 

 an inclination of one in one hundred, three gallons and a half per minute; 

 with an inclination of one in one thousand, one gallon per minute. A two- 



