THE FRESH-WATER AQUARIUM. 13 
have figured (p. 11), is best formed of a slab of slate, and 
the two ends may be of slate also; the front and back of 
plate or very stout crown glass. The most elegant form 
for such a body is that of the double cube, the length of 
the tank being just double its width and depth, so that if 
it were cut into two equal parts two cubes would be 
formed. The glass must be set in grooves in the slate, 
and bound outside with zinc or turned pillars of birch 
wood. The best cement is white-lead putty, or what is 
known as Scott’s cement; the composition of which it is 
not in my power to inform the reader. If a coating of 
shell-lac, dissolved in naptha, and made into a paste with 
whiting, were laid over the white-lead cement, as sug- 
gested by Mr. W. Dodgson, of Wigton, the water would 
be kept from contact with the lead, and the tank would 
require less seasoning. 
The use of slate at the ends is to enable us to affix 
rockwork or carry across a rude arch; the cement used 
in constructing rockwork does not adhere to glass. But 
if rockwork is not thought desirable the slate ends may be 
dispensed with, and the vessel may be composed wholly 
of glass, except the bottom, which may be of slate or 
wood. 
In some districts slate is not to be easily obtained, and 
wood or stone are then the best substitutes, wood being 
preferable of the two. I have seen some handsome tanks 
composed wholly of wood and glass; it is only necessary 
to choose well-seasoned material, and unite the joints very 
perfectly. 
The yellow clay used by potters would be found suit- 
