36 FISH CULTURAL ASSOCIATION. 
ee 
he terms “hospital jars,” the live eggs thus drawn over being 
left to take their chances with the dead ones. 
This mode of treatment undoubtedly has served to diminish 
materially the percentage of loss in the eggs thus treated by him, 
as in this way, by the sacrifice of a small proportion of the eggs, 
he secured the complete separation of all elements of contamina- 
tion and disease from the great bulk of the eggs. 
In 1881, while I was in charge of a shad-hatching station on 
the Potomac River, and in position to observe closely the per- 
formance of the hatching apparatus in use, the question of the 
separation of the dead from the living eggs was taken up sys- 
tematically, with the view of devising a form of apparatus which 
would accomplish the purpose, and which would be of such 
shape as to be of easy and convenient use in practice. Knowing 
that there was an apparent difference in the specific gravity of 
the living and the dead eggs, I determined to see if I could not 
avail myself of this difference to effect the separation. The 
first form of apparatus employed is presented in fig. 1.* 
In the use of this apparatus, ] found that a fair separation 
could be effected, but to accomplishthis required perfect stability 
of the vessel and careful manipulation. When the barges were 
lying quietly on the water, and there was no tide swell in the 
river, the separation went on perfectly, the dead eggs being con- 
tinually thrown off from the mass of living eggs, and swept by 
the current over into the exit trough and carried off from the 
apparatus. The slightest oscillation, however, of the barge, pro- 
duced by waves, would derange the orderly movements of the 
* This consists essentially of an oblong trough with wooden ends and sloping glass sides, 
glass being used in order to be able to observe the movement of the eggs under the influence 
of the currents. This trough rests upon a rectangular box made of boards, which serves at 
once as a firm base for the support of the trough, and as a chamber for the equable distribution 
of the water pressure. The water which enters the rectangular box forming the base of the 
apparatus through the supply pipe I, passes to the trough proper through a slot extending the 
whole length. The influx of the water to the trough is regulated by the valve V V, which, by 
means of the set rods S S, can be pushed down so as to cut off. the flow of water entirely. By 
setting so as to have the opening between the valves and the glass sides about one thirty- 
second of an inch, the water enters the hatching trough in thin sheets which are directed up 
the glass sides of the trough. The effect of this is to give the eggs a continuous movement in 
the direction shown by the arrows. The water flows over the edges of the central trough, 
and escapes from the apparatus at O. The dead eggs in their circuit float higher than the 
living, and the force of the entering current may be so regulated that the former will be swept 
out by the escaping water. 
