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of water, which must not only be replenished, but great judgment 

 was necessary to preserve the specific gravity of the water, or 

 mischief would accrue to the fish. Again, the pumping in of fresh 

 sea water caused a turbidity and milkiness, which must be removed, 

 for the public was not satisfied unless the water was as clear as 

 crystal. To accomplish this, a plan was adopted with very marked 

 success, which originated, he believed, with Mi*. H. Lee. Some one, 

 he rather thought Dr Brehm, mentioned that the moUusca were 

 great agents in clearing sea water, and the late Mr Lord, just before 

 the opening of the Brighton Aquarium, tried mussels, but the 

 diSiculty was to know whether any of them had died, and if so, a 

 greater difficulty was to pick out the defunct ones. Mr. Lee 

 suggested to him that the mussels should be suspended in nets, but 

 still there was a difficulty. At last it sti-uck Mi-. Lee, when he took 

 chai'ge, to try oysters instead of mussels, and with a very mai'ked 

 success. Oysters were still employed in the Brighton Aquarium 

 for the purpose of clearing the water, and this would explain the 

 reason why that mollusk might be seen at the bottom of each 

 marine tank. The capability of cleanng the water by the oyster 

 was not only doubted, but denied, by some. This capability had 

 been demonstrated in his own presence by seeing sea water 

 with and without the mollusk ; that in which the oysters had been 

 placed was clear, that without them was turbid. Any member of 

 the society could easily, at any time, pi'ove the truth of this 

 experiment for himself, and see with his own eyes how the oyster 

 cleared the water. 



Another difficulty was to find out what was the kind of food 

 which difi'ei-ent fish would take, and then an equal, if not greater, 

 difficulty, to induce the fish to eat, for not until then could it be 

 safely affirmed there was a possibility of getting the fish to live. 

 It had, happened, over and over again, that even when the food was 

 well known from experience, and fish of the same kind were 

 thriving on that kind of food, new comers could not be induced to 

 take the same, or any kind, of food. By observing the way in which 

 different kinds of fish always took their food — some as soon as it was 

 dropped into the water, others rising at it, and others taking it 

 while it was passing by them downwards, others only when it had 

 fallen to the bottom, some darting rapidly at their food, others 

 quietly seizing it — a very valuable series of hints for fishermen had 



