26 PURIFICATION. 



be filtered back into it. This is a very simple 

 process : a funnel (if of glass, earthenware, or 

 gutta-percha, the better) is placed over the tank, 

 with a bit of sponge pushed lightly into the top of 

 the tube, so as to allow the water to run through 

 in a narrow, thread-like stream. Eeplace tlie 

 plants and animals, reserving those pieces of rock, 

 or those shells, that look suspicious, which may be 

 kept in a bowl of water by themselves for a few 

 days, till their state appears more fully. 



This process of bringing every drop of the water 

 into contact with the atmosphere, is an effectual 

 remedy for destroying the tendency to putrefac- 

 tion ; as the animal fluids and solids held in sus- 

 pension enter into combination with the oxygen of 

 the air, and form the pure innocuous gas called 

 ozone. The result will be that the milkiness will 

 rapidly disappear ; the water will assume a trans- 

 parent clearness, which will in all probability be 

 permanent ; the plants will thrive, and the ani- 

 mals will be lively. This result will be rendered 

 still more secure by filtering the water through 

 pounded charcoal, and by allowing some pieces of 

 the same substance to float in the Tank. 



Should it happen that, from oversight, or 

 ignorance, or any other cause, putrefaction has 

 thoroughly set in, still you need not lose the water. 

 Take out any animals that are yet alive, as well as 

 the weeds, and then put the water in an open vessel, 

 in some shed or out-house, where the fetor will be 

 of no consequence. Leave it there for the putre- 

 factive process to run its course, which it will do in 

 two or three weeks if the weather be warm. The 

 water will then gradually resume its original clear- 

 ness and purity ; the weeds may now be replaced 



