jars, and anemones,
crabs, shell-fish of various kinds, and many other creatures, will be
found among it. The seaweed should be a day or two in the tank before the
creatures are put into it.

And now, having got the aquarium in order, comes the point how to keep it
in order,--how to keep the creatures alive, and how to prevent the water
from growing cloudy and thick. The main rule is to secure sunlight,--hot
enough to raise the water to a temperature above that of the outer air,--
to remove all dirt and floating scum, and to furnish the tank on every
cloudy day with a supply of air and with motion by means of a syringe. The
creatures should never be fed in warm weather with any animal substance,
its decay being certain to corrupt the water. A little meal or a few
crumbs of bread may now and then be given; but even this is not necessary;
for Nature furnishes all the food that is needed, in the spores thrown off
by the seaweed, in the seaweed itself, whose growth is generally
sufficiently rapid to make up for the ravages committed upon it, and in
the host of infusoria constantly produced in the water. If any of the
creatures die, their bodies should be immediately removed,--though
sometimes the omnivorous crabs will do this work rapidly enough. As the
water evaporates, it should be 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