The Formation and Management of a Marine Aquarium. 2o3 
half an inch in diameter, open at both ends, employed in dipping as repre¬ 
sented in the figure. Lower it carefully with the finger applied until it is 
exactly over the object to be removed. T. hen lift up the finger, and the water 
will rush in, carrying with it the fragment. Apply the finger again and lift it 
out, and you have accomplished your object. 
Remark was previously made on the necessity of maintaining the density 
at its proper standard. Rain-water has a specific gravity of 1,000 ; sea¬ 
water is heavier, its specific gravity is 1,028. As there is always more or less 
evaporation going on, the water becomes 
more and more saline, and consequently 
attains a higher specific gravity, unless 
fresh-water is added as the need for it 
occurs. A specific gravity bulb, gradu¬ 
ated for the purpose, should be kept 
floating in the tank, and in adding 
fresh-water to make good the loss by 
evaporation, enough should be supplied 
to cause the bulb to descend an inch 
or so below the level, and at that point, 
or nearly, it should always be kept. A 
well-doing tank in which the animals 
are fairly proportioned and thoroughly 
seasoned, will not suffer by a little 
neglect of this matter, for if the water 
attains a density of 1,100, the anemones 
and mollusks will simply close and 
become dormant. But of course it is 
better to do things well, for the aquarium 
is not only designed to keep the 
creatures, but also to display them, and any departure from the best 
conditions possible will be attended with a suspension of the exhibition, 
for discomfort will cause the animals to sulk and retire out of view. 
In the case of an emergency, artificial sea-water may prove of immense 
value, but it is never to be used when real sea-water is obtainable. The 
following is a formula for preparing it:—Take 14 oz. (avoir.) of common table 
salt; 1 oz. (avoir.) Epsom salts; 800 gr. (troy) chloride of magnesium; 160 
gr. (ti oy) chloride of potassium ; mix with spring-water, and adding it a small 
