12 
THE FRESH-WATER AQUARIUM. 
are held together on top by strips of a similar material connecting them. 
Of the three materials for the base and pillars, iron is by far the best for 
a fresh-water tank, if we can have but one material alone; it is lighter 
than stone, and the little it rusts from time to time does not amount to 
anything; the water does not ooze through it as it does through some 
kinds of stone, and it does not warp, as wood is apt to do if the tank is 
left without water for a length of time. To prevent rusting a layer of 
cement may be spread on the bottom of the tank inside, and a plate of 
thick strong glass placed upon it; and in the same way a narrow strip of 
glass can be cemented to each of the pillars, so that the iron shall be 
prevented from coming in contact with the water at every point. A tank, 
having a base of slate and pillars of iron protected by glass, as just 
explained, is the best kind of a tank to own, as it can be used for either 
salt or fresh water as we require. The shape of a tank, too, is of some 
importance, that of a double cube being the best for this reason, that it 
allows more of a clear surface on the long sides for inspection after the 
rockwork and plants are introduced, than a tank whose shape is square; 
it also gives abetter chance for the light to strike upon every point inside. 
The facilities for procuring tanks already made are so great nowadays, 
that while once it was an object to know how to construct a tank for 
one’s self, now one has only to make a choice from several patterns. 
The most important thing to look after in selecting a tank, next to its 
material and shape, is the kind of cement which has been used; all sorts 
of putty are to be rejected as worthless; if we cannot be sure that the 
cement is good and not injurious to fishes, a few weeks trial, or even 
less, will convince us of its value. Another point to be attended to, is 
that the cement be quite hard before the tank is filled with water, as there 
are some kinds of cement used that never harden; of course, in these 
cases there is danger of having a leaky tank with which to contend 
®f the other kinds of tanks, either those made wholly of clay, or of 
glass, or those with one side at an angle of 50° with the base, so as to 
form a beach, after the pattern of the Warington tank, or those with all 
the sides of slate, in imitation of a rock pool, or those of an oval or hex¬ 
agonal shape, each has its advocates. Some tanks have been lately made 
in New York, with the base and pillars of a composition which is silver- 
plated ; they are wonderfully light and beautiful, but there seems to be 
doubts as to their durability. More or less ornament can be displayed on 
the pillars and base of the tank, according to the taste of the owner, but 
it seems as if simplicity and neatness were fully as requisite here as else- 
