546 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[8] 



such a diameter that the water rising above the outer edge does uot 

 completely fill them. 



The water descends like a long veil along the inside of the pipe, pro- 

 ducing a strong current of air, which rushes down with the water. I 

 do not think that these pipes are constructed for the express purpose 

 of acting as air-injectors; but, howsoever this may be, it is none the less 

 true that they serve this purpose in a very efficacious manner. 



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Tig.1. 



The manner in which the water enters the individual hatching-boxes 

 may also be a means of introducing air into the water. I refer particu- 

 larly to the practice which I observed in the establishment of ISTeuhausen 

 and also in that of Dachsen. In the Kcuhausen establishment the 

 water, which from the general distributing reservoir is made to gush 

 through a pipe at same height above two troughs, first enters a square 

 box, whence it descends along the short sides like a waterfall, as shown 

 in Fig. 1. 



At Dachsen the water flows through stop-cocks into common terra- 

 cotta flower-pots, the bottom hole of which is purposely somewhat en- 

 larged. The pot rests on a piece of metal sheet, on which are placed a 

 number of small pebbles. As the distance between the mouth of the 

 stopcock and the pebbles in the flower-pot is sufficient to allow the 

 stream of water to spread out somewhat, and to break itself on the peb- 

 bles with a certain force, the water comes in constant contact, "with the 

 air, as shown iu Fig. 2. 



