* * 
ill ,3 
Tanks for Marine Aquaria . 
a few pieces of mica-schist may be mixed with them and left alone, and 
there will soon be plenty. 
Another advantage of these tanks is their strength. When properly made, 
they will last a lifetime without becoming leaky, which cannot be said of any 
vessel having four sides of glass. Perhaps four-fifths of the glass tanks made 
and sold at the first start of the aquarium are now in lumber-rooms inhabited 
by spiders, and the majority of their owners have given up aquarium pursuits, 
under an impression that the construction of water-tight tanks is an impossi¬ 
bility ; whereas the Warrington tank, having three sides of slate, can be made 
sufficiently strong to endure a lifetime. The amateur who constructs his own 
vessel must be on his guard against the folly of attempting to make it light; 
the heavier the better, 
consistent with neat¬ 
ness and soundness 
of the joints. 
A still more im¬ 
portant advantage of 
the slope-back tank 
is the equable tem¬ 
perature of the water 
within it. Even if 
the sun's rays be al¬ 
lowed to play on the 
back of the vessel— 
which they should 
not—there is so large a bulk of slate for them to heat before the water can 
be affected, that there are no sudden changes of temperature to destroy 
the lives of the inmates. Vessels of this sort are therefore essentially cool , 
and during the trying months of July and August marine animals will endure 
the heat with patience, when, in any vessel having glass sides, they would 
perish rapidly. 
The improvements since effected have rendered this form of vessel 
still more acceptable than it was originally. On the principle that the larger 
the bulk of water the greater the variety of creatures that may be preserved in 
it, a form was adopted by which the triangular space under the sloping back 
is converted into a water chamber, communicating with the space in front. 
Into this chamber none of the animals can find access, and in one sense the 
WATER CHAMBER SLOPE-BACK TANK. 
