This section is from the book "Fish Hatching, And Fish Catching", by R. Barnwell Roosevelt, Seth Green. Also available from Amazon: Fish Hatching, And Fish Catching.
Practically there is but one line for fly-fishing, either for salmon or trout, the braided silk covered with a water-proof preparation, and tapered. We have a fondness theoretically for the horse-hair line, on account of its lightness, but we never use it now. The superiority of the water-proof line is so marked in every point but lightness, which in itself is a qualified advantage, that no one at present uses any other. It should be tapered at both ends, in order to turn it end for end as it wears out, the first portion to give way being that which is most exposed. These lines were at first only made in England, but now they are being generally manufactured here, of a quality scarcely if at all inferior to the imported article.
The trout line is from twenty to thirty yards long, according to the size of fish it is expected to catch, and the salmon line is one hundred yards in length. The latter is heavier in the center, but they both taper to nearly equal fineness. Weight is necessary to make a long cast, or to cast at all well against the wind; and a splash in the water is avoided by the taper and the casting line. Such a line will last a lifetime with care, and without care will outwear a half-dozen of the best horse hair lines. ever made. It never has to be dried, except out of abundant caution in case the entire roll on the reel should get soaked. It is strong and reliable, and has no weak places. It will not cut, and it does not catch in the rings of the rod. Old fishermen who read these words, and who have used hair lines, will appreciate the weight of what we say.
The hair line is lighter, and can be made under certain circumstances, to fall more gently on the water, but in recommending fine tackle we do not mean to recommend any that is too fine to be practical. Some men use a light, limber rod in bass fishing, because, as they say, it takes them longer to kill their fish. This is Miss Nan-cyism, and there is nothing we despise more. Use the most effective tackle under all circumstances; for coarse fish, strong line and rod; for shy fish fine lines and gut leaders, but always that which will kill the most in the shortest time, and with the greatest ease and certainty. When you go sailing for blue fish it would be a folly to use a line so thin that it would cut your hands and might not hold your fish; but in casting for trout in clear water, you must fish far and fish well, and to do this the water-proof line, all things considered, will be found to be the best.
 
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