ARTIFICIAL HATCHING OF SPAWN. 



39 



his greenhouse, shown at (Z>) in the section of the 

 cistern, in which, on a lofty frame, a large slate 

 cistern was placed capable of holding 200 gallons. 

 Various experiments were tried, and Mr. Ponder 

 found that this cistern would contain enough to 

 allow a good stream, of about five-eighths of an inch 

 in diameter, to flow for twelve or thirteen hours 

 without running the cistern dry, so that it had to be 



SECTION OF CISTEEif. 



pumped full morning and evening. The water was 

 received into the cistern, through a large fine sieve 

 (c) of double horsehair, and thus all leaves, insects, 

 and foreign matters, were caught in it, and could not 

 pass to the cistern ; and as this sieve could be lifted 

 off at will, the contents could be cast out from it 

 every morning. Near the bottom of one end of the 

 cistern was a stop-cock (e), by which the flow of the 



