P. S. I forgot to say I was thirteen years old and have a brother nine years old, who thinks the ST. NICHOLAS "a dandy," as he expresses it. * * * * * MORE ABOUT CURVE-PITCHING. LINCOLN CO., NEB. DEAR ST. NICHOLAS: The two letters in the February number on "curve-pitching," I was very glad to see. It was during my college-days that the "curve" made its appearance, and it was for some time a matter of much interesting discussion among us. I was not much of a base-ball man, but I saw a good deal of curve-pitching, and occasionally threw some rather wild "curves" myself in an amateurish way. We budding physicists discussed the why and wherefore of the problem, but never arrived at any satisfactory solution. The same explanation which is given in the second letter of your February number suggested itself to me at the time, and I was quite satisfied with it until I discovered that it did not accord with the facts of the case. It is a beautiful theory, but, like some other theories, it doesn't work. According to the theory, as shown by your correspondent, the ball rotating (as indicated by his diagram which he gives), against the hands of the watch should curve to the right, producing the _in_ curve. But the fact is, that a ball so rotating will curve to the left--the _out_ curve. And a ball rotating in a contrary direction, _i. e._, so that points on its forward side are moving to the right, will curve to the right--the _in_ curve. In both cases the axis of rotation is vertical, so that the motions of the ball may be well illustrated by a spinning-top, as is shown in the first letter by A. D. S. But the case of a rifle-ball in motion does not seem to me to be parallel with that of a base-ball under normal conditions. A rifle-ball is given a rotation about an axis parallel to and coincident with its line of flight, just as an arrow rotates on its shaft. Now, none of the curves of a base-ball are produced with the axis of rotation in this position. In the _in_ and _out_ curves, as already said, the axis of rotation is vertical; while the _rise_ and _drop_ are produced by rotating the ball about a horizontal axis perpendicular to the line of flight. In _all_ cases the axis of rotation _must_ be at right angles to the line of flight, and the more accurately this condition is complied with, the more marked the effect. My knowledge of the subject is too slight to warrant me in asserting that the curving of the rifle-ball and that of the base-ball do not depend on the same principle, but it does not seem to me that the two are identical, for the above reasons.