filled up to its original level with fresh spring-water,—­the salts in it undergoing no diminution by evaporation.  If, suddenly, the water should grow thick, it should be taken from the tank, a portion at a time, and filtered back into it slowly through pounded charcoal, the process being repeated till the purity seems to be returning, and at the same time the rocks and seaweed should be removed and carefully washed in fresh water.  If, however, the water should by any ill chance grow tainted and emit a bad odor, nothing can be done to restore it, and, unless it is at once changed, the creatures will die.  To meet such an emergency, which is of rare occurrence, it is well to have a double quantity of the salts sent with the tank to secure a new supply of water.  But we have known aquariums that have kept in order for more than a year with no change of the water, a supply of spring-water being put in from time to time as we have directed; and at this moment, as we write, there is an aquarium at our side which has been in active operation for six months, and the water is as clear as it was the day it was put in.  If, spite of everything, the seawater fail, then try a fresh-water aquarium.  Use your tank for the pond instead of the ocean; and in the spotted newt, the tortoise, the tadpole, the caddis-worm, and the thousand other inhabitants of our inland ponds and brooks, with the weeds among which they live, you will find as much entertainment as in watching the wonders of the great sea.

A camel’s-hair brush, a bent spoon on a long handle, a sponge tied to a stick, and one or two other instruments which use will suggest, are all that are needed for keeping the sides of the tank free from growth or removing obnoxious substances from its bottom.

If, on receiving the animals, any of them should appear exhausted by the journey, they may sometimes be revived by aerating the water in which they are by means of a syringe.  It should always be remembered, that, though living in the water, they need a constant supply of air.  And it would be well, in getting an aquarium, to have the tank and the seaweeds sent a few days in advance of the stock, so that on the arrival of the creatures they may be at once transferred to their new abode.

There are no American books upon the subject, and, in the present want of them, the two whose names are given above are the best that can be obtained.  Mr. Gosse’s is expensive, costing between four and five dollars.  “The Common Objects of the Seashore,” to be got for a quarter of a dollar, contains much accurate, unpretending, and pleasant information.

The American Drawing-Book:  a Manual for the Amateur, and a Basis of Study for the Professional Artist.  Especially adapted to the Use of Public and Private Schools, as well as Home Instruction.  By J.G.  CHAPMAN, N.A.  New York:  J.S.  Redfield. 4to. pp. 304.