12 U. S. BUREAU OF FISHERIES. 



which are also made of cypress 1| inches thick, are 8^ inches wide, 

 and between the uprights they are supported by steel brackets. The 

 condensation from the jars is drained into the troughs through a 

 groove cut along the outer edges of the shelves. At one end of each 

 trough is a galvanized iron overflow. The supply of water to the 

 batteries is regulated by automatic Ford tank valves, and the dis- 

 charge, after entering the catch box, is carried to the basement 

 sewer. Wlien the fry are hatching the water is carried, as shown, 

 to the fry building, and under the whole length of the batteries 

 galvanized pans are provided to catch the drip, which drains into 

 the basement sewer. There are 11 jars on each shelf between the 

 uprights, making 198 jars in all on each side of a battery, or 398 

 jars per battery. 



This type of battery is compact and neat in appearance. By 

 means of the grooved shelves and drip pans the floors are kept 

 dry, and, as each trough is provided with a drain plug, they may be 

 scrubbed at any time without interfering with the operation of the 

 jars, the attendant stepping along the jar shelves. At all the bureau's 

 hatcheries it has been found best to use the natural water supply 

 without attempting to modify its temperature, but good results in 

 the incubation of whitefish eggs can not be expected in a water tem- 

 perature much above 50° F. In early November, when the white- 

 fish spawning season in Lake Erie begins, the water in the Put in 

 Bay hatchery ranges from 40 to 48°. About December 1 it drops to 

 approximately 35 to 38°, and after the lake freezes, or as soon as 

 ice in any appreciable quantity forms, the temperature of the water 

 passing through the jars remains uniform at 32^°. Around the 

 middle of March, when the lake is usually free from ice, the water 

 temperature rises slightly. The fry begin hatching about this time, 

 and as a rule the incubation period is completed in the first week of 

 April. 



Every year prior to the opening of the spawning season the in- 

 terior surfaces of all troughs and tanks are well covered with as- 

 phaltum varnish. As a first coating, when the wood is new, white 

 lead and oil are applied, followed by two coats of varnish, the latter 

 consisting of one part turpentine to two parts asphaltum. The best 

 asphaltum pitch is used for filling the cracks and joints, first soften- 

 ing it with paraffin to the consistency of chewing gum, or so that 

 it will not break in cold water. This pitch holds firmly to the wood 

 and keeps its place in warm weather. Other pitches that have been 

 tried are likely to run in warm weather and to harden with use, 

 breaking wheii cold. All jars, tubes, troughs, etc., should be kept 

 scrupulously clean. 



CAKE AND PLANTING OF FKY. 



Wlien the fry hatch, they immediately leave the jars and follow 

 the course of the running water, those in the upper tiers going 

 through the succeeding jars, and all finally reaching the fry-collect- 

 ing tank at the bottom, whence they are carried to the main col- 

 lecting tanks. It has been urged by some that it is injurious for the 

 fry to pass down through the lower jars with the complement of 

 egg-s, but in practice this has not been the case. 



