The whole idea of casting a fly is to drop it in the most likely-looking places and to strike the fish just as soon as he seizes the hook. To do this we must always have the line under perfect control, therefore do not attempt to cast a line too great a distance. If we do not fix the hook into the fish’s mouth at the instant that he seizes the fly, he will very soon find that what he thought was a nice fat bug or juicy caterpillar is nothing but a bit of wool and some feathers with a sting in its tail, and he will spit it out before we can recover our slack line. It is a common mistake to use flies that are too large. Ordinary trout flies are the proper size for bass and the smallest size trout flies are plenty large enough for trout. There are hundreds of kinds of flies of various combinations of colours and no one can say which is the best. This question has been argued by fishermen ever since the days of Izaak Walton. The universal rule of trout and bass fishermen who use a fly is to select small dark flies for bright days or when the water is very clear or low and the more brightly coloured ones when the day is dark or the water dark or turbid. The fly book should contain a varied assortment to meet these conditions. The best lines for fly fishing are made of braided enamelled silk. Some fly lines are tapered but this is not necessary and is a needless expense. Twisted lines are much cheaper but very unsatisfactory. Fly fishing is not only the most scientific and sportsmanlike method of fishing but it is also the most difficult to acquire skill in. It is of course possible to catch trout and salmon on other bait than flies. In fact, there is really no better bait for brook trout than common fish worms that have been scoured in sand. The use of a fly, however, is more satisfactory where the pleasure derived in fishing is more important than the size of the string. [Illustration: An artificial fly; used for salmon] In learning to cast a fly, you can practise at home, either in an open space or wherever there is room to work the line. It is not necessary to practise with the actual hooks or flies on the line. Simply tie a knot in it. Hold the rod lightly but firmly in the right hand. Point your thumb along the line of the rod and start by pulling out a little line from the reel with the left hand. With a steady sweep, cast the end of the line toward some nearby object and with each cast pull out a little more line until you reach a point when you are handling all the line you can take care of without effort or without too much of a sweep on the back cast. You must not allow the line to become entangled in trees or other obstacles. The wrist does most of the work in casting. The elbow should be close to the side. If you find that the line snaps like a whip on the back cast, it is because you start the forward cast before the line straightens out behind.