Page:Natural History, Fishes.djvu/30

16 which constantly ran a small and irregular supply of waste water, about thirty brace of perfectly healthy Trout were turned, varying from three quarters of a pound to a pound each, and taken from a neighbouring mill-pool. The pool into which the Trout were turned, in the month of August, contained a great quantity of Roach, some Carp, Tench, and Perch, all healthy and thriving Fish: but the Trout, when taken out during the summer, and the following season, seemed to have increased very little in weight. With the exception of one healthy Fish of three pounds, nearly all the others were found to be either entirely blind or partially so, and doubtless would soon have died of starvation, as they were black, thin, and poor beyond belief. Those which were not too far gone to recover, I turned into a neighbouring brook: but what could have caused this effect upon the Trout alone, when all the other kinds of Fish, upon being taken out of the same water, were healthy and in perfectly good condition, I am at a loss to imagine. In the early part of the following March, I caught one of these Trout of about two pounds, which I had the preceding summer turned into the brook; and although it was of a very good colour, silvery and bright, it did not appear to be well fed, though no defect in the eyes could be perceived. Doubting whether to kill it or turn it in again for another day, I placed it in a small hoop-net, while I tried for another Fish, and threw the net into the stream. After taking two smaller Trout in very good condition, I took up the net and was surprised to perceive this silvery bright Fish become perfectly black; so that but