MANUAL OF FISH-CULTURE. 109 



THE HATCHERY. 



The hatching- trough or tank in use at i»rorthville combines the prin- 

 ciples of both the Clark and the Williamson hatching apparatus and 

 is therefore called the Clark-Williamson hatching-box. It possesses 

 more advantages than any other in use for the development of a large 

 number of eggs; a thorough circulation is obtained for thousands, the 

 apparatus is simple, and the eggs may be readily handled for picking, 

 cleaning, etc. It consists of a trough of any length according to the 

 number of fry to be held, 18| inches wide inside and 1 foot deep, with 

 partitions to divide it into compartments, and is constructed as follows: 

 Only the best IJ-inch pine is used, all planks containing knots, heavy 

 pitch, etc., being rejected, and the sides and ends are each made of but 

 one piece of lumber. The bottom is made first, the strips of different 

 widths plowed and tongaed securely, and all joints laid in white lead. 



Referring to figs. 1 and 3, page 110, three-quarters of an inch down 

 from the top of the sides is a f-inch groove (A) running the entire length 

 of the trough. The partitions, dividing the trough into compartments, 

 18f inches by 9^ incnes by 12 inches, are mortised ^ inch in the sides ; 

 the first and each alternate partition (B) is fixed ^ inch from the bottom 

 of the trough to allow the water to pass under it ; the seciond and each 

 alternate partition (C) is mortised into the bottom, and at the top is cut 

 out so as to leave a space llf inches long by 1^ inches deep for the 

 water to pass over. In tlie bottom of the boxes thus formed a ^ inch 

 strip (D) ^ inch wide is nailed to the sides; upon these the bottom trays 

 rest. A crossbar (E), with |-inch block (F) to hold the trays securely 

 in place and prevent them from rising in the water, is made to fit in the 

 grooves at the sides of the trough. 



The capacity of the troughs may be doubled by the addition of a 

 second row of boxes, one side of the first tank acting as a partition 

 between the two rows. Each box holds eleven trays (G). Ten of these 

 are filled with eggs, the eleventh, or top one, acting merely as a cover 

 to prevent the eggs on the tenth tray from being carried off by the 

 current. The trays are made of ^-inch mesh galvanized wire cloth, 

 tacked upon frames 16 inches long, 7 inches wide, and f inch thick. 

 Both the trays and tanks are given three coats of asphaltum paint 

 before being used, and one coat at the beginning of each succeeding 

 season. Eleven of such trays, in the box described, will fill the com- 

 partment to within | inch of the groove in the sides of the tank; then 

 the crossbar with the |-inch feet holds them securely in place. The 

 tanks are set upon iron standards cemented in the floor, and are given 

 a pitch of I of an inch to the foot. The height of the tank from the 

 floor is a matter of convenience to the operator, depending on the fall 

 of water available. 



The water enters through a 1-inch pipe at the head of the tank, flow- 

 ing down through the first division, up through the second, and so on 

 to the lower end. Where water is scarce, two troughs maybe made to 



