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entering into its construction should be allowed to come in contact with 
the sea water. The form of tank I have found so successful is of an 
oblong shape, three feet long, eighteen inches wide, and nine inches 
deep, and capable of containing sixteen gallons; its bottom, back, 
and two ends are of slate, and the front of stout plate glass; these 
are all firmly bolted and cemented together, and all the joints are 
perfectly water-tight. Inclining from before, upwards and back- 
wards, at an angle of about fifteen, with the glass in front, is a slate 
false bottom placed. This should not fit too accurately round its 
edges, so that if necessity requires its removal, no difficulty may be 
experienced in doing so. The object of this inclining false bottom 
is worthy of being borne in mind, as it is of some importance. It 
affords, in the first place, a varying depth of water, enabling your 
animals to select the depth most suited to them, and secondly, it 
divides the tank into two compartments, that under it being filled with 
water which is always cool and in a state of rest, while that above 
it is exposed to the light, and actively engaged in ministering to the 
animal and vegetable life growing in it, and a compensating action 
always takes place within these two compartments which very 
materially aids in keeping the water in a wholesome and healthy 
condition. The great object to be kept in mind in working an 
aquarium is to assimilate its conditions as much as possible to those 
of natural rock pools. All attempts to construct grottoes, arches, 
or temples, or, in short, any such like ornamentation, are to be 
strongly deprecated ; but. sandstone rock-work, roughly disposed, is 
of much use, affording shelter for your stock, and,-by extending the 
superficial area of the bottom, increasing the aérating capacity of 
the vegetation which will ultimately clothe it. This rock may be 
cemented on the sloping bottom with Portland cement, but none 
must be placed on the sides of the tank, as that would interfere 
with the removal of the false bottom, should that be required. 
: Care must then be taken to thoroughly soak the rock-work and 
: cement for a fortnight, or even longer, frequently changing the 
} water, that all soluble matters may be removed from them. When 
you feel sure that these are sufficiently soaked, and that no more 
lime will be eliminated from the cement, you may move on a step 
further. While some forms of animal life cling to the rocks, others 
will burrow in the sand, therefore a supply of this must be added. 
If you are not in a position to get sea sand, an excellent substitute 
may be found in the silver sand sold at any of the oil shops, and for 
an aquarium the size of mine, two gallons will not be too great a 
quantity. This must be repeatedly washed till the water is quite 
clear when the sand is stirred up in it, and then it may be placed 
in the tank. Everything being now ready for the sea water, this 
brings me to the second division of my subject. The water em- 
ployed may be artificial or natural sea water. Of course, where 
attainable, the preference ig given to real sea water, because how- 
