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 suggested 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-
