42 FISH CULTURE. 



fervse, and advised a filter to be applied. There was 

 some difficulty in applying it in a mechanical point 

 of view, and it proved fortunate, indeed, as matters 

 turned out, that the temperature of the water did not 

 permit the confervas to grow. Had it done so, I fear 

 that hardly an egg would have escaped — for being 

 desirous of watching the entire process closely, my 

 friend deposited the ova on the gravel instead of 

 under it, and thus all sediment settled directly on 

 the ova. 



A rough filter, in such cases, is very desirable; 

 one of the large-size flower pots, with side holes, 

 every hole being corked but one, would, I imagine, 

 answer well enough, a layer of fine gravel being 

 placed in it first, say two inches deep ; then a layer 

 of charcoal, of the size of beans and peas, and then 

 another layer of gravel ; turn the water on to this, 

 and, I think, a filter effective enough would be the 

 result ; a spare one should be kept at hand, to ex- 

 change in case of the filter getting foul. 1 Half of the 

 troughs were filled to within an inch of the small 

 delivery pipes, noted above, with fine gravel well 

 boiled. The other half had, over beds of gravel not 

 quite so high in the boxes, planes of slates fixed ; 



1 With streams a bed or bank of sand and gravel will form a very- 

 tolerable filter. 



