HOW TO FOKM. 21 



most of the plants recommended for the Aqua- 

 vivarium will live in ordinary water. 



The water, when the Aquavivarium is well 

 managed, will generally remain clear and bright, 

 and all that will be required will be the addition 

 of fresh water as evaporation diminishes the ori- 

 ginal stock. Accidents, however, continually hap- 

 pen ; the possessor of an Aquavivarium failing to 

 discover the first portentous signs of a coming 

 epidemic amongst his plants and animals, will 

 find them suddenly overwhelmed ; the water will 

 become turbid, and smell ; myriads of animalcules 

 and locomotive plants will be developed ; and the 

 death of all or most of the higher organisms result. 

 Patience will even restore this state of things, for 

 the water is there, and the water itself never 

 decomposes j it may become ice, or vapour, but it 

 never changes its elementary constitution. It is 

 best, however, under these circumstances, to change 

 your -water, save what you can from the wreck, 

 clean off the Confervse from the side of your tank 

 and jar with some sand or pumicestone, and begin 

 afresh. 



This kind of visitation may be prevented in the 

 same way that cholera and fever are prevented in 

 our towns. In the first place look to your refuse ; 

 if your scavengers are not doing their duty, dis- 

 charge them and get better. Remove the dead, 

 always have recourse to extramural interment ; 

 this applies to dead leaves as well as dead bodies, 

 these should be all removed. If you feed your 

 animals, take care that the superabundance is not 

 left to rot, as it is sometimes in our markets, to the 

 injury of those who do not want it or cannot get it. 

 If you recollect that decomposing animal and vege- 

 table matter is a source of unmitigated evil every- 

 where, you will keep a sharp eye on your Aqua- 



