Page:Popular Science Monthly Volume 92.djvu/916

 �Jeff Tesreau, the star pitcher of the Giants, about to baf- fle the bat- ter with his great spitball

��I Underwood and Underwood

��NO definite explanation of the vaga- ries of the spitball or the "shine" ball has ever, so far as I am aware, been given. I have seen many generaliza- tions, but no specific explanation, and so I am now essaying the task in the hope that it may prove interesting, and possibly serviceable, to players of baseball.

Definite and consistent curves in base- ball, or swerves, as they are called in cricket, can be produced only by spin imparted to the ball by all the fingers and thumb or some of them.

Comparatively few people know that the "top" of a wheel moves more quickly through the atmosphere than the "bot- tom"; yet this is undoubt- edly so. The reason is that at the "top" of the wheel the motions of revolution and progression "conspire" or coincide. To put it, perhaps, a little moje simply we may say that the wheel is going forward and is rolling for- wardly, therefore at the top we have the sum of these two motions.

It is otherwise at the bottom of the wheel. Here, as this portion of the wheel is revolving backwardly, the rotary mo- tion conflicts with the progressive motion,

���Spitball Myths

Why pitched baseballs curve and why the spitballs are scientifically foolish

By P. A. Vaile

[Author of "Swerve, or the Flight of the Ball," "Modern Golf," "Modern Tennis")

��and instead of the sum of two motions, we get the difference. Of course all por- tions of the wheel \'iewed as a whole are progressing towards its destination at the same rate. It is merely that certain constantly-changing portions are moving through the atmosphere at different speeds.

That, shortly, is the whole secret of curve or swerve, for the side of the ball whereon the motions conspire sets up more friction with the air than that on which they conflict. A projectile always seeks the line of least resistance, there- fore the ball is forced over toward the side where the spin is backward.

I may here repeat that there is, so far as I am aware, absolutely no other means whereby definite and consistent curves with a ball can be obtained. If there be, and anyone can tell us of them, the scien- tific world will be much interested.

This brings us to a consideration of the spitball and the "shine" ball. Any curve that these balls have is not due to the action of the air on the wet or shiny patch on the ball.

It is due to the amount of spin that is imparted to them by the pitcher on ac- count of those patches. What finally decides the nature of the spin on any ball must necessarily be the last point of con- tact between the ball and the player. If a ball is held, say, mainly by two fingers and a thumb, and pitched from that hold, the flesh grip of the three engag- ing members may be ap- proximately the same, except for the force of gravity's bearing the ball down on the lowest of the three, and the push of any downward action in the throw.

Now, suppose that the portion of the ball remote, or farthest away from the lowest engaging member, naturally. in

��The Spitball

Spin A to B. Flight D to E. Therefore spin and proRression conspire at portion shaded dark, C. At portion F, the spin is against the progression. Consequetitly, the ball is forced towards F', as there is less friction there than at C

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