MANUAL OF FISH-CULTURE. 129 



two-thirds coal tar. The tar should be as warm as the touch will bear, 

 and the turpentine, which should be pure, should be added slowly while 

 the mass is being vigorously stirred. The mixture dries quickly and 

 forms a hard, durable surface, which is entirely waterproof and much 

 more lasting than asphaltumj it is also much cheaper, an important item 

 in a large station. While applying it the tin pail in which it is mixed 

 is kept in another and larger one partly filled with moderately hot 

 water. For pitching the cracks and joints the best asphaltum pitch is 

 used, softened with paraffin to the consistency of chewing-gum — that 

 is, just 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 which 

 have been tried will run in warm weather and get hard with use, 

 breaking when cold. 



THE CARE AND PLANTINft OF THE FEY. 



When the fry hatch they immediately leave the jar and follow the 

 course of the running water, some going through the succeeding jars, 

 provided there are no screens interposed to prevent this, others through 

 the overflows from the cross-tanks, until all reach the fry-collecting 

 tank at the bottom, whence they are carried to the main collecting 

 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 eggs, but in 

 practice this has not been the case. 



An air -jet on the inside of the screens will prevent clogging by the 

 accumulation of eggshells and impurities sus^^ended in the water. This 

 may be easily arranged by j)roviding an air-pump and connecting with 

 it a pipe carried along the side of each tank on the inside of the screen 

 and thence at right angles parallel to the screen and about an inch 

 distant. This cross-pipe should be perforated on one side with holes 

 -gAj inch in diameter and 3 inches apart, the holes opening toward the 

 screen and upward at an angle of about 45°. When the air is turned 

 on, an apparently solid mass of bubbles will arise along the whole sur- 

 face of the screen. With this arrangement the screens will run hours 

 or even days without any attention, whereas without the air-jet one or 

 more men are employed keeping the screens clean, and many fry are 

 unavoidably killed by being forced against the screens and by the work 

 of the men in keeping them free. The thorough aeration of the water 

 thus indirectly accomplished is very beneficial when large numbers of 

 fry are passing over, and double the number can be safely handled in 

 troughs thus equipped. 



At Put-in Bay the fry are planted as soon as hatched. They are 

 dip])ed from the fry tanks into kegs, in which they are transported to 

 the natural spawning-grounds on the reefs; each keg containing 50,000 

 to 100,000 fry, according to the distance to be traveled. If they are to 

 be taken any considerable distance, fresh water is kept running on 

 them. If the facilities are such that the fry can be held in tanks until 

 they attain a length of an inch before being planted, they would be 



F. C. K. 1897 9 



