II.-A REPORT OF THE WORK OF THE UNITED STATES FISH 

 COMMISSIOiN STEAMER FISH HAWK, FOR THE YEAR ENDING 

 DECEMBER 31, 1881. 



By Lieutenant Z. L. Tannek, U. S. N., Commanding. 



At tbe close of my last report, December 31, 1880, the vessel was at 

 the Uuited States navy-yard, Norfolk, Va., where she remained until 

 February 26. The work of i)ainting and refitting was completed about 

 the middle of January, and a series of experiments with the hatching 

 machinery carried on during the montlis of January and February, 



It was considered desirable to introduce air with the feed-water on 

 its entrance to the hatching cones for the purpose of economizing water, 

 and, in order to mix the two sufficiently to prevent violent ebullition by 

 the rapid ascent and explosion of large air bubbles at the surface, we 

 experimented with numerous forms of simple aerators, succeeding 

 finally, as far as practicable, without 

 first reducing the feed- water to a spray. 



B^. 1 is a vertical sectional view of 

 the aerator (full size), a a is the outer 

 case into which & & is screwed; c, the 

 feed-pipe connection; d, the nozzle over 

 which the upper end of the flexible feed- 

 pipe is attached ; e e, air-holes. 



Fig. 2 is an end view, b h is the noz- 

 zle to which the feed-i)ipe is attached ; 

 c, feed-pipe connection ; e e e c c e ce, air- 

 holes. 



The feed-water entering at c and the 

 air at e e meet and find their way into 

 tlie bases of the hatcluug cones partially 

 mixed, that is, the feed-water is impreg- 

 nated with numerous small air-bubbles. 



Experiments were instituted also with 

 a view of adapting the cones to cod-fish 

 hatching. 



Sliad eggs, for which the hatching 

 apparatus on board this vessel was de- 

 signed, sink rapidly and require a con- 

 stant upward current to prevent n)atting or settling at the bottom in a, 

 solid mass. Cod-fish eggs, on the contrary, float upon the surface of 

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