MANUAL OF FISH-CULTURE. 37 



in other respects will this answer, and even then it is only admissible 

 where there is an ample snpply of aerated water and the troughs are 

 very short and there is absolutely no danger of inundation; and this 

 fall has the disadvantages of the impracticability of introducing any 

 aerating- apparatus and the necessity of having- the troughs sunk below 

 the rtoor of the hatcliing-house, which makes the work of attending the 

 eggs and iish very laborious. 



A fall of 1 foot will do fairly well if there is entire safety from inun- 

 dation, as this will permit the troughs being placed on the floor, which 

 is a better position than below it, though still an inconvenient one, 

 and some of the simpler aerating devices can be introduced. Better is 

 a fall of 3 feet, and far better a fall of 6 feet. The latter permits the 

 placing of the lowest hatching-troughs 2 feet above the floor and leaves 

 ample room for complete aeration. The necessities of the case are 

 dependent largely upon the volume and character of the water, and 

 if there is plenty of it, well aerated before reaching thehatching-honse, 

 there is no occasion, in a small establishment, of additional aeration in 

 the house, and therefore no need of more than 3 feet fall. 



Inspection of the premises at time of floods will suggest the safe- 

 guards necessary to provide against inundation. If located by a brook- 

 side, the hatching-house should not obtrude too much on the channel, 

 and below the house there should be an ample outlet for everything that 

 may come. By clearing out and enlarging a natural watercourse much 

 can often be done to improve an originally bad site. 



In a cold climate it is an excellent plan to have the hatching-house 

 partly under ground, for greater protection against outside 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 water from lake, river* or 

 brook 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 to such 

 an extent as to be a serious annoyance, and if not watched will form 

 in the hatching-troughs so deeply 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 located 

 and constructed that it may be left without a fire for weeks without 

 any dangerous accumulation of ice, and if the site does not permit of 

 building the house partlj^ under ground the walls must be thoroughly 

 constructed and banked well with earth, sawdust, or other material. 

 In warmer climates no trouble will be experienced from this source. 



DAMS AND CONDUITS. 



The requisite head of water can often be had by throwing a dam 

 across the stream and locating- the hatching house close to it. The 

 dam will form a small pond, which will serve the triple purpose of cool- 

 ing, aerating, and cleansing the water. But unless the character of 

 the bed and banks of the stream are such as to preclude any danger 



