262 A Brief History of a Marine Tank. 



description follows, was to endeavour to discover a way of 

 making a marine tank take care of itself, and which must of 

 course wholly depend upon the arrangements made in the first 

 instance. 



On the 24th of June, 1862, 1 fitted up a Warrington slope- 

 back tank in my study. It was placed with its back to the 

 window and at about fifteen inches from the glass, so as to 

 receive but a moderate amount of daylight, and that wholly 

 through the glass cover ; light from the front being impossible. 

 The tank is made wholly of slate, except the front, which is 

 plate glass, and the back is placed at an angle of 40, which, 

 leaves a hollow cavity at the back ; there is therefore no water 

 chamber. The capacity of the tank is twenty gallons. Pre- 

 vious to fitting this tank I had by me a considerable quantity 

 of debris from former experiments, and I set out in the full 

 sun a large collection of old shells of oysters, whelks, serpulge, 

 and other odd gatherings that had lost their interest because 

 their inmates had perished. Conspicuous amongst these were 

 some pieces of tile and rock thickly coated with acorn 

 barnacles. Fearing there might be some gelatinous matter, 

 the result of deposition when the animals perished, I placed 

 them in a vessel of water for a few days to dissolve out any 

 organic detritus, and then placed them in the sun to be 

 thoroughly sweetened. These several materials were used for 

 covering the sloping slate back of the tank, and their adoption 

 was a most decided gain ; in fact, they soon told me that heavy 

 blocks of mica-schist or any other rock were wholly unnecessary. 

 These slate tanks are very heavy, and it is not desirable, 

 unless a house is built expressly to receive them, to increase 

 the weight by piling up rockwork inside them. In my case 

 any serious addition to the combined weight of tank and water 

 might cause the whole affair to subside from the study at the 

 top of the house to the bed-room immediately below it, which 

 would be an unpleasant circumstance, especially if it happened 

 at night. But the bank of rocks at the back of the tank may 

 be said to weigh nothing at all, consisting as it does wholly of 

 old shells, and some of them very large, handsome, finely per- 

 forated and richly clothed shells of oysters from which the 

 inmates departed many a year before. I found the shells 

 weather-beaten on the beach. Please make a note of this 

 therefore, and if you are fitting up an aquarium, secure for it a 

 few hampers of sea-side findings of an ancient shelly kind, 

 and let the chief bulk consist of the largest and most ancient 

 of the beach-strewn oyster shells that can be obtained. They 

 are worth all tho cost of carriage and moro to an enthusiast in 

 those matters, as will be seen presently. 



The tank was fitted with these substitutes for rock, and 



