1897.1 MICROSCOPICAL JOURNAL. 43 



as it certainly is in the case of a salt-water one. The 

 amount of water it is to hold must, of course, settle its 

 actual size ; but, as a rule, it should be said that no tank 

 should be deeper than it is wide, and its length should 

 be about twice as long as its width. To descend to par- 

 ticulars : to hold 12 gallons the tank may be about 27 in. 

 by 16 in. by 14 in. deep. One to hold up to 20 gallons 

 will be about 36 in. long by 22 in. broad by 18 in. deep. 



As to the actual structure of the tank, this, of course, 

 depends very much upon the taste of the maker. Person- 

 ally, I think the plainer the tank is (within limits) the 

 better. It is the fishes and plants, etc., that are the ob- 

 jects of attraction — not a gorgeously ornamented tank. 

 For this reason I look upon all ornamental "tops," brass 

 fringes, etc., round the edges, and carved images on the 

 pillars, etc., as abominations. If the tank is to have a 

 top it can be composed of two perfectly plain pieces of 

 glass, each the width of the tank frame and rather less 

 than half its length, thus leaving a little strip between 

 them when they are placed in position, through which 

 the air can get at the water. If the beetles, etc., show 

 a disposition to get out the vacancy can afterwards be 

 covered with a strip of perforated zinc. The glass is, of 

 course, held in its place by fitting into a rabbet in the 

 upper surface of the frame, in which it can lie. 



The following will, 1 hope, be sufficiently explicit 

 directions as to the actual manufacture of the tank for 

 those who have never constructed anything similar before. 

 The first thing to do is to make the bottom. For this I 

 have tried plain wood, wood painted and varnished, and 

 wood covered with glass and cement, and am decidedly of 

 opinion that wood in any form is to be avoided. The 

 best thing to use is a tolerably thick slab of slate, and 

 taking my first dimensions of the tank as an example, I 

 think for this the slab ought to measure about 29 in. by 

 18 in. by 2 in. thick. This allows of a width of an inch 



