I wish I had been at the county fair when Arthur Dart’s father offered ten dollars to any one who would successfully perform the “three stake proof,” as I am certain that I should have made that amount by the operation, whether I had been asked to pitch the “in” or “out” curve, both of which I find equally easy to accomplish. The question of why the ball curves after it has left the hand, I account for as follows: If the “in” curve is to be pitched, the ball touches the index finger the last thing before leaving the hand, and, as it does so, the hand is quickly and forcibly clenched, so that the ball is given a twirling motion. Therefore it curves to the right (provided it is thrown with the right hand). In the case of the “out” curve, the ball touches the thumb the last thing before leaving the hand, and consequently twists to the left, producing the “out” curve. The “out” curve is so called because it is a ball thrown to a right-handed batsman when in position, so that it curves _out_ toward the end of his bat, while the “in” curve is a ball thrown to a batsman which curves _in_ toward his body. The following may be safely taken as a rule as to curve-pitching. If the ball be thrown so it twists the way shown in Fig. 1, the ball will curve in; but, if it be thrown so it will twist as indicated by Fig. 2, the ball will curve out. [Illustration: FIG. 1.] [Illustration: FIG. 2.] Trusting that this explanation is clear and satisfactory, and hoping to see it in the “Letter-box,” I remain the stanch friend and admirer of our National Game, WILL P. SNIKPOH. * * * * * FISHKILL, N. Y. DEAR ST. NICHOLAS: I have been reading with much interest the letters concerning the curving of a base-ball, and would now like to try my hand at offering an explanation. The theory that I present is not original, being taken from “Wood’s Analytical Mechanics,” p. 462, but it seems to be the one offering the best explanation of the actual facts of the case. I will omit what mathematics there is in it, in order to render it a little more easily understood. [Illustration]