As instances of the difference in this respect between large and small rivers, I may quote the Vockla and the Agger in Upper Austria. The first of these rivers, when I fished in it in 1818, was full of trout and grayling, and I believe I was the first person, for at least many years, that had ever thrown an artificial fly upon it. It is a small stream, from eight to fifteen yards wide, and can every where be commanded by the double-handed rod, and is generally shallow. The first day that I fished in this stream, which was in the beginning of August, at every throw I hooked a fish, and I took out and restored again to their element in the course of a few hours more than one hundred and fifty trout and grayling. The next day I fished in the same places, but with a very different result: I caught only half a dozen large fish: the third morning, going over the same ground, I had great difficulty even to get a brace of fish for my dinner, and those, as well as I recollect, I caught by throwing in places which had not been fished before. I ought to mention, that the space of water where this experiment was made did not exceed half a mile in length. I shall now speak of the Agger, which is a much larger and deeper river than the Vockla, and cannot be commanded in any part by a double-handed rod, being at least from forty to sixty yards across. The first time I fished this river, I had the same kind of sport as in the Vockla; the second day, under the same favourable circumstances, there were fewer rises than on the first day, but still sufficient to give good sport; and it was the fourth day before it became difficult to catch a good dish of fish, and necessary to seek new water. The greater depth of the water, and the change of place of the fish, particularly the grayling, explain this, to say nothing of the greater number of fish which the larger river contained. I am, of course, speaking of one of the best periods of fly-fishing, when many large flies, of which imitations are easily found, have been on the water. In spring (a bad season for fly-fishing in high Alpine countries) I have thrown great varieties of flies on these two highly stocked streams, and have found it difficult to get a brace of fish for the table, as the trout and grayling were all lying at the bottom, not expecting any _winged food_ at this season.