948 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



as much as a one-inch hole. A cylindrical tube whose length is three 

 times its diameter will vent 29 per cent, more water than a hole of same 

 diameter through a thin plate or board. 



3.— SITE. 



A satisfactory supply of water having been found, it is next necessary 

 to select a site for the hatching-house that combines in as great a degree as 

 possible the various desiderata, of which the most important are, first, 

 facilities for creating a head of water to provide for the requisite fall into 

 and through the troughs ; second, security against inundation ; third, if in 

 a cold climate, security against too much freezing; fourth, general safety 

 and accessibility. 



The fall required in the hatching-house cannot be stated very definitely, 

 but it can hardly be too great. The minimum for the most favorable 

 cases is as low as three inches, but only under the most favorable circum- 

 stances in other respects will this answer, and even then it is subject to 

 several very serious disadvantages. It is only admissible where there is an 

 ample supply of aerated water, and the troughs are very short, and there 

 is absolutely no danger of inundation ; and the disadvantages are the im- 

 practicability of introducing any aerating apparatus and the necessity of 

 having the troughs sunk below the floor of the hatching-house, which 

 makes the work of attending the eggs and fish very laborious. 



A fall of one foot will do pretty well if there is entire safety from in- 

 undation. This will permit the troughs to be placed on the floor instead 

 of below it, (a better position, though still an inconvenient one,) and some 

 of the simpler aerating devices can be introduced. Better is a fall of three 

 feet, and far better a fall of six feet. The latter will allow the lowest 

 hatching-troughs to be placed two feet above the floor, to the great relief 

 of the backs of the attendants, and leave ample room for complete aera- 

 tion. Of course the necessities of the case are dependent largely upon 

 the volume and character of the water. If there is plenty of it, and if 

 it is well aerated before reaching the hatching-house, there will be no 

 occasion in a small establishment of additional aeration in the house, and, 

 therefore, no need of more than three feet fall, and, except for convenience 

 in working and for guarding against inundation, one foot fall is enough. 



As to liability to inundation, actual inspection of the premises at time 

 of floods will generally suggest what safeguards are needed. 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 water-course 

 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, which will protect it wonderfully against outside 



