HAL.—I think it must be another species of the same genus; the same as Back’s grayling found by Captain Franklin and his companions in North America, and distinguished by a much larger back fin. Having travelled with the fishing-rod in my hand through most of the Alpine valleys in the south and east of Europe, and some of those in Norway and Sweden, I have always found the char in the coldest and highest waters; the trout, in the brooks rising in the highest and coldest mountains; and the grayling always lower, where the temperature was milder: and if in hot countries, only at the foot of mountains, not far from sources which had the mean temperature of the atmosphere,—as in the Vipacco, near Goritzia, and in the streams which gush forth from the limestone caverns of the Nordic Alps. Besides temperature, grayling require a peculiar character in the disposition of the water of rivers. They do not dwell, like trout, in rapid shallow torrents; nor, like char or chub, in deep pools or lakes. They require a combination of stream and pool; they like a deep still pool for rest, and a rapid stream above, and a gradually declining shallow below, and a bottom where marl or loam is mixed with gravel; and they are not found abundant except in rivers that have these characters. It is impossible to have a more perfect specimen of a grayling river than that now running before us, in this part of its course. You see a succession of deep still pools under shady banks of marl, with gentle rapids above, and a long shelving tail, where the fish sport and feed. Should there be no such pools in a river, grayling would remain, provided the water was clear, and would breed; but they cannot stem rapid streams, and they are gradually carried down lower and lower, and at last disappear. You know the Test, one of the finest trout streams in Hampshire, and of course in England; when I first knew this stream, twenty years ago, there were no grayling in it. A gentleman brought some from the Avon, and introduced them into the river at Longstock, above Stockbridge. They were for two or three years very abundant in that part of the river; but they gradually descended, and though they multiplied greatly, there are now scarcely any above Stockbridge. There were, four years ago, many in the river just below; but this year there are very few there, and the great proportion that remains is found below Houghton. I ought to mention, that the water is particularly fitted for them, and they become larger in this river than in their native place, the Avon,—some of them weighing between 3 and 4lbs. The trout, in all its habits of migration, runs upward, seeking the fresh and cool waters of mountain sources to spawn in: the grayling, I believe, has never the same habit of running up stream; I never saw one leaping at a fall, where trout are so often seen. Their large back fin seems intended to enable them to rise and sink rapidly in deep