38 
THE FRESH-WATER AQUARIUM. 
We take then two or more pieces of stone, having very rough edges 
so as to look more natural and place them about a foot apart, if 
the tank will admit of such a width, making a height of about two 
inches. Upon the tops of these pillars of support we place a thin 
flat stone, large enough to rest firmly on them and even lap over 
an inch or so on each side ; then upon this flat stone we place the 
pillars of another bridge, having the next flat stone somewhat 
smaller than the other and so on until we have made so many 
bridges, that the top of one will just reach the surface of the 
water. The distance between these flat stones may vary ac¬ 
cording to the fancy of the builder. The top stone makes a little 
island and gives such animals as tritons and turtles an opportunity 
to come out and take the air, or sun themselves. Another use 
this top stone may be put to is this, — to support a small collection 
of marsh plants, making a great ornament to the aquarium. 
Many of the fern-like mosses found growing on the rocks in damp 
places in the woods, or the swamp cowslips or violets, or the beli- 
cate plants of sundew (Drosera rotundifolia) , or some of the kinds 
of arrowheads ( Sogittaria ), do perfectly well if planted in a very 
small quantity of soil upon this top stone. Our native pitcher 
plant (Sarracenia purpurea), and the red cardinal plant ( Lobelia 
cardinalis ), seem especially adapted for this purpose. If we take 
the former plant up in the fall and keep it growing upon the top 
stone until March, it will then begin to throw out its buds, and, 
before long, blossom most curiously. The latter plant seems to 
to do best when taken up with the buds just appearing, and it will 
last long enough in flower to repay one for all the trouble of trans¬ 
planting it. Various other means of beautifying the top stone 
ma}^ be adopted. If we wish a small collection of tropical ferns, 
and have room enough, w^e may cover them with a glass shade and 
have a diminutive Wardian-case, forming a part of the aquarium. 
It is the custom with many to make a mound of marine-shells, 
or of coral, in the centre of the tank ; besides being dangerous to 
the water from the difficulty of getting them perfectly clean, they 
seem quite out of place, not only because thay are foreign to fresh 
water, but because it seems that the aquarium should be a place 
for living, not for dead specimens. It is far better to avoid 
putting in any shells, however beautiful they may be in the cabi¬ 
net. Having completed the rock-work and washed every stone 
carefully as it is put in, the plants are next to be attended to. In 
