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strongly recommend is one constructed on equally scientific princi- 
ples, and equally capable of natural arrangement as a shelving 
rocky pool, with the advantage of a picture-like effect when viewed 
from the front. The proportions of this tank may be as follows:— 
breadth two-thirds of the length ; depth two-thirds of the breadth ; 
for example : length 36 inches; breadth 24 inches; depth (outside 
measurement) 16 inches. 
This tank should be fitted with a false bottom, sloping from 
the front to the back, where it should terminate at about four 
inches from the top. ‘The sloping platform should have irregular 
lines of pieces of stone or slate cemented to it, forming ledges on 
which rock-work may be arranged. Viewed from the front the 
effect is extremely beautiful when the aquarium is well-stocked 
with sea-anemones of various forms and colours, and the rock- 
work has assumed the rich appearance imparted to it by the delicate 
growths of spontaneous vegetation which soon tint every stone and 
shell. 
The sloping platform in this tank not only provides a graduated 
depth of water, and enables the interior to be seen with good 
effect, but a very important udvantage is gained by the formation 
of a triangular space beneath the false bottom, which is perfectly 
dark, and contains nearly the same quantity of water as the upper 
portion of the tank. Through crevices at the sides—not large 
enough for any of the animals (except the minutest) to pass 
through—the water in the two chambers is in communication, and 
a slow, but constant, circulation is set up by the difference in the 
temperature of the two compartments. The darkness of the lower 
chamber tends to keep the water clear by checking the development 
of the spores which always abound in the water, only awaiting 
the influence of a certain amount of light to germinate and render 
the aquarium thick with vegetation. This valuable improvement 
in the construction of Aquaria was the invention of Mr. E. 
Edwards, of Chester. It was adopted and strongly recommended 
by the late Mr. Lloyd, and has, I believe, been patented. 
* * * * The best materials for the tank are slate and 
glass, the bottom, back and ends being formed of slate, and the 
front consisting of a sheet of good plate glass. Two sheets of 
plate glass should be provided as moveable coyers for the aquarium, 
the smallest opening between the two being sufficient to admit air 
for surface oxygenation. The object of the covers is to prevent 
loss by evaporation as well as to protect the water from dust. 
* * % * The most suitable position fora marine aquarium 
is in front of a window facing the north, north-east, or east. The 
order of suitability of other aspects is north-west, west, south-east, 
south-west, south. The last two are very objectionable because of 
the difficulty of keeping down the excessiye light and heat in 
summer. In any aspect the light will require to be carefully 
