PHYS.—You are in the right; the fish I have is a large trout—at least he is not much less than 2lbs. I have landed him; shall I keep him? HAL.—As you please: he is as good as he ever was, or ever will be in this water. PHYS.—There are now more yellow flies out than I have seen before this season. They have appeared suddenly, as if sprung from that large alder. Though you gave us in a former conversation some account of the flies used in fishing, yet I hope you have not forgot your promise, to favour us with some more details on this subject, which, both as connected with angling, and with a curious part of natural history, is very interesting. HAL.—I wish it was in my power to give you information from my own experience, but, I am sorry to say, this has been very limited; and though the English are peculiarly the fly fishing nation, yet our philosophical anglers have not contributed much to this department of science, and what has been done is principally by foreigners, amongst whom Swammerdam, Reaumur, and above all De Geer, are pre-eminent. To attempt to collect and apply the knowledge accumulated by these celebrated men, would carry us far beyond the limits of a day’s conversation; and as a great proportion of the insects that fly, walk, or crawl, are the food of fishes, a dissertation, or discourse on this subject, would be almost a general view of natural history. You know that frogs, crawfish, snails, earthworms, spiders, larvæ of every kind, millipedes, beetles, squillæ, moths, water flies, and land flies, are all eaten by trout; and I once heard the late Sir Joseph Banks say, that he found a large toad stuck in the throat of a trout; but as the skin of this animal is furnished with an exceedingly acrid secretion, it probably had been disgorged after being swallowed by a fish exceedingly hungry. But though I have found most of the insect tribes, and many small fishes, even of the most ravenous kind, as pike, in the stomachs of trout, it never happened to me to see a toad there. I might give you an account of the birth and life of frogs, which, with respect to their generation, resemble fish, and which, when first excluded from the egg, may be considered in the tadpole state as fish; and you would not find their singular metamorphosis without interest. Or I could detail to you the true histories which naturalists have given of the habits of snails and earthworms, and of the sexual relations of these apparently contemptible animals;—but this is too delicate a subject to dwell on. Even the renewing or change of shell in the crawfish, when it falls in its soft state an easy prey to fish, is a curious inquiry not only for the physiologist, but likewise for the chemist. On these points, I must request you to refer to writers in Natural History: yet I shall perform my promise, and say a few words on winged insects, which, in their origin and metamorphosis, offer the most extraordinary known miracles perhaps of terrestrial natures.