54 THE SEA SHORE 



We will begin with an aquarium constructed entirely of a 

 mixture of cement and fine sand, this being the most inexpensive 

 and certainly the easiest to make ; and although it may not be 

 regarded as the most ornamental but opinions will differ on this 

 point yet it has the decided advantage of being the nearest 

 approach to the natural rock pool. Though somewhat heavy and 

 cumbersome, even when empty, the amount of material used in its 

 construction may be varied according to the taste and convenience 

 of the maker. Further, this form of aquarium is one that will 

 readily admit of structural alterations at any future period. It 

 may be deepened at any time ; lateral additions or extensions may 

 be made, or a portion may at any time be shut off for the purpose 

 of isolating certain of the animals procured. 



The first thing to do is to prepare a flat, strong slab of hard 

 wood or stone, the exact shape and size of the desired artificial 



FIG. 34. SECTION or AN AQUARIUM CONSTRUCTED WITH A MTXTUKE 

 OF CEMENT AND SAND 



pool, and then cover this, if of wood, with a mixture of fine sand 

 and cement, mixed to a convenient consistency with water, to the 

 depth of about one inch. The banks or walls of the pool must then 

 be built up on all sides, and this is best done by the gradual 

 addition of soft pellets of cement, applied in such a manner as to 

 produce an irregular surface. Unless the walls of the aquarium 

 be very thick and massive the cement will soon show a tendency 

 to fall from its place as the height increases, but this may .be 

 avoided by doing the work in instalments, allowing each portion to 

 set before further additions are made to the structure. 



Since some marine animals like to occupy snug and shady 

 niches in deep water while others prefer full exposure to the light 

 in shallows, arrangements should be made for all by varying the 

 depth of the bed, and providing several little tunnels and caverns. 

 This may be accomplished either by working the cement itself into 

 suitable form, or by means of piled stones obtained from the sea 



