128 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



The cross-tauks are in steps, like a fliglit of stairs, which accounts 

 for the unequal lengths of the supply-troughs. Each has an overflow 

 in the center, over which a small amount of water is kept runniug, so 

 that the attendant can see at a glance that all of the troughs are full. 

 Screens are interposed at such places in the cross-tanks that the fry 

 discharged into them through the waste-troughs can not enter the oppo- 

 site supply-troughs, but will float with the overflow successively into 

 the lower cross-tanks down to the fry-collectiug tanks. 



The fry-collecting tanks, one for each battery, are connected with the 

 main collecting tanks by means of 2-inch gas-pipe, fitted with valves, 

 passing under the floor of the hatchery. The main tanks, eight in 

 number, are 3 feet wide, 16 feet long, and 2 feet deep ; iu these the fry 

 are retained until dipped out for shipment or planting. 



The only marked difference between the method of operating the jars 

 at Put-in Bay and other stations is the use of a finch iron gas-pipe, 

 instead of a glass tube, for supplying the jars with water, and the addi- 

 tion of a tin cone, 6 inches long and 1 inch in diameter at the lower 

 end, which is soldered to the end of the iron xiipe and reaches within 

 one-eighth inch of the bottom of the jar. The tube is held in place by 

 an iron bracket, fastened to the supply-trough and held by a thumb- 

 screw. The cone has the eflect of spreading the water and giving an 

 easier and more thorough motion to the eggs than can be obtamed with 

 a straight tube. 



At Put-in Bay the water passes through eight rows of jars, and the 

 fact that the eggs in the lower rows of jars are just as good as those 

 in the upper rows is proof of the practicability of the plan. 



The jars require C quarts of water per minute to each jar on the top 

 row, this amount again supplying the successive tiers of jars on the 

 shelves below. If more jars are placed on the lower shelves than on 

 the top one, a greater quantity of water must necessarily be added, 

 e(iual to 6 quarts of water to each jar. 



The temperature of the water must, of course, with the large quan- 

 tities used, be what nature makes it, but if much above 50° F. good 

 results can not be expected with whiteflsh eggs. When the work 

 begins, early in November, the temperature of the water in Lake Erie 

 is from 40° to 50° P., while late m the month it is generally about 35"^ 

 to 38°. As soon as the lake freezes over, or ice in any considerable 

 quantity forms, the temperature of the water as it passes through the 

 jars remains very uniform at 32i°. When the ice goes out, which is 

 generally about the middle of March, it rises slowly, and wlien the fry 

 begin to hatch, the latter part of the month, it is generally up to about 

 33° or 34°. 



The jars, tubes, troughs, etc., should be kept scrupulously clean. 

 The usual coating for the inside of troughs and tanks is asphaltum 

 varnish, but a mixture of coal tar and turpentine has proved au excel- 

 lent substitute. For the first coat on new wood equal parts of eacli 

 are employed; for the second and third coats one-third turpentine and 



