20 THE AQUAVIVARIUM. 



arranged in it ; care should be taken to introduce 

 it at the side through a funnel, or what is better, 

 use a water-pot with the rose on. The water is thus 

 gently added, and, what is of advantage, it gets 

 aerated in passing through the atmosphere ; and 

 should you be going to add your animals directly, 

 it will be of service to them. But you should wait 

 a few days before the animals are put in, as by this 

 means the water gets charged with oxygen from 

 the plants. 



Now comes the kind of water. Almost any 

 water may be employed for this purpose which is 

 used for drinking. Perhaps of all kinds of water 

 the Thames, as supplied to the houses of London, is 

 the best, as, from containing a dash of sewage 

 without enough to destroy the animals, it affords 

 manure to the plants. Rain-water answers very 

 well, and there is no objection to spring or pump 

 waters, as long as their saline constituents do not 

 make them mineral water. Chalybeate springs are 

 very injurious to vegetation. 



In addition to the carbon, oxygen, hydrogen, and 

 nitrogen, which plants obtain from carbonic acid, 

 ammonia, and water, they require certain saline 

 constituents. These they get from the water ; so 

 that, provided they are not in so large quantities as 

 to destroy life, water is the better for containing 

 some of them. It is perhaps questionable if either 

 plants or animals would live and grow in perfectly 

 pure water ; some plants flourish in proportion to 

 the quantities of these saline matters the water 

 contains ; thus the Charas grow best where there 

 are considerable quantities of carbonate of lime ; 

 the Grass-wrack (Zoster a marina) and a host of 

 other plants grow only in salt-water. Some Con- 

 fervse grow where the water gives out sulphuretted 

 hydrogen. These, however, are exceptions, and 



