[15] CONSTRUCTION AND WORK OF FISH-ilAWK. 1 7 



carefully graduated flow of fresh water through the vessels in which the 

 eggs are placed for development. In the early days of this industry 

 shad eggs were hatched in floating boxes with gauze bottoms anchored in 

 a tide way or current which eftected the necessary- change of water, but 

 they were subject to various accidents beyond the control of those hav- 

 ing the operations in charge. A sudden squall might capsize them, a 

 gale of wind break them from their moorings, or drift-wood carry them 

 away, the entire charge of eggs being liable to loss or serious damag* 

 in either case. 



Various other methods have been used with good results, but for 



service on shipboard, under all conditions of wind and weather, the cone 



• is thus far the most perfect appliance for hatching non-adhesive eggs, 



with greater specific gravity than the water in which they are developed. 



To prepare for shad hatching with cones, water is pumped into the 

 distributing tanks, which have independent connections for each set of 

 cone frames through which the water flows by gravity into the upper or 

 feed-piijes, where, at proper intervals, small feed-valves are tapped in 

 and connected to the base of the cones by a flexible hose. The feed- 

 valves being opened, a stream of water is admitted at the bottom, 

 rapidly filling them till near the toj), where a fine wire gauze rim is en- 

 countered. Through this the water finds an outlet to the discharge con- 

 nections, thence to the waste pipes at the bottom of the frames, and into 

 the general delivery; thus establishing a steady and constant upward 

 current. 



From 100,000 to 200,000 impregnated eggs are placed in each cone 

 and the current regulated by the feed-valves so as to give them a gen- 

 tle movement, just suificient to prevent "matting," or settling to the 

 bottom in a mass, where they would soon become asphyxiated. The 

 dead eggs being lighter soon accumulate at the surface, and are re- 

 moved with a skimmer, sediment and other impurities being cleared 

 from the gauze rims to allow an unobstructed flow of waste water to the 

 discharge-pipes. 



Development takes place rajiidly, and the embryo is hatched in from 

 two and a half to five days, according to the temperature of the water. 



HATCHING CYLINDERS. 



There are in addition to the cones eighteen hatching cylinders, which 

 are suspended, nine on each side, from beams outside of the vessel and 

 operated by a cam motion imparting a vertical movement of about H 

 inches. (See Plate III.) They have wire-gauze bottoms, aud both solid 

 and wire-gauze covers, the former used when the cylinders are converted 

 into transporting cans, the latter in stormy weather. The cylinders 

 are made of heavy tin and the mountings are brass. 



To prepare for shad hatching they are suspended from the beam, as 

 shown in Plate III, in such a manner that the bottoms will be constantly 

 submerged ; from 250,000 to 300,000 impregnated eggs are placed iu 

 S. Mis. 110 2 



