APPENDIX. 253 



zinc, &c. It may be also, if naturally not very 

 clear, filtered through gravel, charcoal, &c. ; and 

 the top box may be devoted to this service. It 

 is not necessary that the boxes should be placed 

 on the side of a hill, as represented in the drawing ; 

 but still they should be placed one above the other, 

 in such a manner that there should be a fall from 

 one to the other, l^or is it absolutely necessary 

 that the end of the upper box should rest on that 

 immediately below it. The water may be con- 

 ducted from one to the other by means of a trough 

 or plate (with the margins turned up) of common 

 zinc. The pond at the end of the boxes will re- 

 ceive the fish ; but they should not be allowed to 

 escape there till the umbilical bag is gone. The 

 pond must not be above three or four feet deep ; or 

 if it be naturally deep, the margins must be made 

 to slope, as the young fish like shallow water to 

 bask, feed, and play upon. They must be fed 

 for a time when in this pond. The boxes should 

 have solid boards, or boards fitted with perforated 

 zinc, made to fit their tops by means of hinges and 

 padlocks, to keep out all intruders — biped, quad- 

 ruped, or aquatic. 



IN-DOOR APPARATUS. 



Page 91. 



As I have said in the text, the in-door is far 

 preferable to the out-door apparatus. The accom- 

 panying drawing shows the troughs best suited for 

 the purpose, each is fitted with a lip which con- 

 ducts the water from one to the other. They can 

 be multiplied one above the other ad infinitum. 



