|61] FISHERIES OF THE UNITED STATES. 1215 



McDonald's universal hatching- jar — Continued. 



15 inches ; diameter, G inches $ capacity, 5 quarts. Patented 

 by Marshall McDonald, Washington, D. 0., in 1882. XT. S. Fish 

 Commission. 57,186. The McDonald jar is successfully em- 

 ployed in the hatching of various species of heavy eggs. The 

 water in entering is thrown against the bottom with considerable 

 force, and is deflected upward around the sides of the jar. The 

 eggs, which tend to settle to the bottom, are carried upward 

 along the sides, thence inward toward the center, from which 

 point they again sink to the bottom. The current is regulated 

 to give the desired motion to the eggs. With heavy eggs like 

 those of the salmon there is no motion, but the water coming 

 from beneath tends to buoy the eggs upward, thus preventing 

 any injurious pressure on the lower ones by the mass above. 

 The outflow pipe is movable, and can be lowered to a poiut 

 where the dead eggs, which are lighter than the good ones, 

 come in contact with it and are carried off. By this means the 

 eggs are kept comparatively free from the injurious effects of 

 fungous growth or decaying eggs. The jar can be filled two- 

 thirds full of eggs with very satisfactory results. Sixty thou- 

 sand shad eggs are considered a fair quantity. 



McDonald hatching jars. 



Photograph showing a nest of hatching-jars on the deck of steamer 

 Lookout employed by the TJ. S. Fish Commission in shad- 

 hatching in the Maryland and North Carolina waters. Size, 

 8 by 10 inches. Washington, D. C, 1882. 2,282. U. S. Fish 

 Commission. 



McDonald hatching- jars. 



Photograph showing a nest of hatching-jars on the deck of steamer 

 Lookout employed by the' TJ. S. Fish Commission in shad- 

 hatching in the Maryland and North Carolina waters. Size, 

 30 by 40 inches. Enlarged by electric light from an 8 by 10 

 negative. Washington, D. C, 1882. 2,282. U. S. Fish Com- 

 mission. 



d. MECHANICAL APPARATUS. 



Parker's rotating hatcher. 



A windlass connected with a system of cog-wheels, which commu- 

 nicate motion to the hatching-cylinder by means of an endless 

 chain. The cylinder is made of perforated tin and wire cloth, 

 to admit of a free circulation of water. On the inside, sus- 

 pended from the axis, is the small basket or trough which con- 

 tains the eggs. Diameter of hatching-cylinder, 10 inches; 



