HOW TO FORM. 19 



one, two, three, or more inches, according to its 

 size. The plants which are to be cultivated may 

 then be placed in it, with a pebble or shell here 

 and there to keep them down, as in adding the 

 v/ater they may be washed away. After this is 

 done, the surface may be then covered, according 

 to taste, with pebbles, shells, and pieces of rock. 

 Some regard, however, should be paid to the natu- 

 ralness of the scene ; large marine shells and lumps 

 of coral are unnatural inhabitants of miniature 

 fresh-water lakes, they are quite natural in the 

 marine Aquavivarium, but here care should be 

 taken not to overload the bottom of the tank or 

 jar: large masses of such objects are unnatural and 

 inelegant at the best ; arches, and other artificial 

 arrangements, are also to be objected to on the 

 same ground, they occupy space, and what is 

 wanted to be shown are the plants and animals, 

 and not a miniature city overwhelmed with water, 

 and inhabited by fish and snails. 



The objection to all forms of mud and clay, 

 where they can be dispensed with, is the thickening 

 of the water whenever they are disturbed ; this 

 disturbance is sometimes necessary in the removal 

 or addition of plants, but it more frequently arises 

 from the fish, which are in the habit of taking up 

 the loose soil and ejecting it again from their 

 mouths. When sand is employed, it speedily falls 

 to the bottom ; but where chalk or clay is present, 

 it is a long time before it is deposited. 



The next thing to be added to our Aquavivarium 

 is water. A little water may be added to the sand 

 before the plants that require it are set : when this 

 is done, the rest of the water may be poured into 

 the vessel. But this requires caution ; if the water 

 is emptied from a spouted mug or can, the chances 

 are, it will wash up the soil and all the plants 

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