I could easily cite numerous instances which have occurred in both my own experience and in that of other anglers which go to prove the effectiveness of the floating fly on low, clear water, late in the season, when the wet fly is usually ineffectual. Without, however, going into narrative detail, it should be sufficiently obvious that, under the conditions named, a very delicately dressed floating fly, in appearance quite similar to the natural ephemeridae common to the stream, attached to a practically invisible leader and riding down buoyantly on the surface, with wings erect, in the exact, jaunty manner of the natural dun, is far more apt to deceive the fish than two or more wet flies, shapeless and draggled, of dubious coloration, pulled across or against the current in a manner never followed by the natural insect. Wherever a fly may be floated the dry fly is distinctly the thing for late spring and summer fishing.
Much has been said and written concerning the character of the streams favorable for the employment of the dry fly--that is, as regards the natural characteristics of the water itself, whether fast or slow in current, smooth or broken, shallow or deep, and so on. The dry fly having originated upon the placid currents of the south of England rivers, it is only natural that the impression should prevail that a floating fly can be used effectively only on a slow stream. The practice and experience of American fly-casters has thoroughly proved this an erroneous theory. It may be truthfully said that the dry fly may be successfully used upon all except white water.
It is not the rate of the current which determines the suitability of the floating fly to any given stream; wherever the surface of the water is unbroken the dry fly works well, but where white water prevails, although the angler may persist in the use of the dry fly, actual dry fly fishing is impossible, the fly can only be made to float for an infinitesimal length of time, is almost immediately drowned by a wave or drawn under by a whirlpool, and the result is a hybrid sort of angling in the nature of wet fly fishing with a dry fly.
The point has been made that even under these conditions it is best to use the dry fly on the ground that, dry or wet, the floating fly is materially, in form and coloration, a better imitation of the natural fly than is the average wet fly. Under like circumstances the natural insect acts in a similar manner, that is, is drawn under the surface in broken water and carried here and there by conflicting currents. For some time it has been my custom to use dry flies for wet fly fishing, but I would emphasize the fact that fishing a drowned dry fly in white water is hardly genuine dry fly fishing and that any resultant success must be accredited to the wet fly method. Any statement to the effect that the dry fly may be used in the rapids of any trout stream where white water is the rule must be taken with a grain of salt and with due allowance for the enthusiasm of the man who makes it.