The usual way in which the slack-line cast is made may be described as follows: The angler, in lengthening out his line, strips from the reel a number of feet more than will be necessary to reach the spot where he desires to place the fly; then, the line having been extended, in making the final forward cast the rod is momentarily but decidedly checked when half way, or possibly a little more, through the forward swing, with the result that the line is doubled back upon itself and the fly settles down upon the surface at the end of a considerable loop of line and leader. The motion of the rod should be stopped only for an instant, and the rod should then be carried down to its usual position at the end of the forward cast, about parallel with the water. A variation of the above method of casting a slack line, one which the writer has found very useful at times, while essentially similar to the method described, differs somewhat in that a loop of slack line, drawn from the reel by the left hand while "lengthening-out," is prematurely released, when making the last forward cast, the result being that the extra line does not "shoot" out straight, but comes down curved and slack upon the surface. To make the slack-line cast and place the fly accurately--as when casting to a rising trout--is a matter of much practice, and, it may be admitted, sometimes equally a matter of much good luck.
Although the matter of striking a rising trout will be treated in a subsequent chapter, it should perhaps be noted here that the seasoned wet fly fisherman, accustomed to fishing a fairly taut line, will soon learn to strike his trout with the loose line most often used in dry fly casting with really fewer resultant misses than is the average when using the sunken fly and a tight line fished downstream or partly down and across. That the average angler whose dry fly knowledge is confined wholly to a greater or lesser familiarity with the literature of the subject, seriously doubts his ability--or that of any man--to strike his fish successfully with a slack line is, I am sure, a fact; and this identical thing, possibly more than anything else, is responsible for the hesitancy with which the confirmed wet fly fisherman turns to the dry fly. In point of fact, the trick is soon picked up and the angler finds his percentage of trout well-hooked really larger than when wet fly fishing.