Now, in continuation of this brief and simple exposition of some of the
points of the Professor’s theorising--backed up by constant practical
experiment--upon the merits of under-spin in prolonging and lengthening
the flight of the ball which created excited comment in the world of
golf at the time, much smaller as that world was then than it is now, it
may be mentioned that it was his fair conclusion that good driving lay
not in powerful hitting, but in the proper apportionment of good hitting
with such a knack as would give the right amount of proper spin to the
ball. Thus, while a player who gave no spin to his ball might attain a
carry of 136 yards, another one who hit his ball with just the same
force, giving it the same initial speed, but also a moderate amount of
under-spin, would get a carry of 180 yards. Of course there would be a
great difference between the trajectories of the two flights. By an
experiment on a small scale he showed very conclusively what under-spin
did. By shooting a ball from a very weak bow, but with the string just
below the middle of the ball, so as to impart a slight spin, he made the
ball fly point blank to a mark thirty yards off. When he drew the string
to the same distance, but applied it to the middle of the ball, it fell
eight feet short. It had no under-spin the second time.
Another point is extremely interesting. Some golfers no doubt think
that in driving they have to cock their balls up in the air, so to
speak; that is to say, that they have to aim at an upward trajectory
from the beginning. As a matter of fact they have to do nothing of the
kind, and as a matter of common knowledge the best balls, as driven by a
Vardon or a Braid or any other first-class player, always “start low”
and keep a path quite close to the ground for some distance, after which
they begin to rise. If there were no under-spin the ball could not keep
this horizontal path for the time that it does; still less could it
begin to rise afterwards. It is the under-spin that does it, and the
theoretically perfect drive is the one that is hit straight forward with
practically no initial elevation or incline. The character of the stroke
gives to the ball the necessary under-spin and power to rise, and the
way in which the club comes on to the ball in a stroke so perfectly
executed makes any considerable initial elevation impossible, just as it
is not wanted. But mark, that if the golfer has not acquired the proper
knack of driving--_i.e._ the proper knack of imparting just the right
kind and right amount of underspin--then he will need some initial
elevation in order to keep his ball in the air; and so he has to depart
intentionally from the proper principles of driving, and deliberately
cock up his ball, even though slightly. How his driving suffers in
consequence may be gathered by taking the extreme case of no under-spin
at all, upon which Professor Tait says: “When there is no rotation there
must be initial elevation, and even if we make it as great as one in
four, the requisite speed of projection for a carry of 250 yards would
be 1120 feet per second, or about that of sound.” Now, as the actual
speed of projection in the case of a fine drive by a first-class player
is not more than 350 feet per second, the reader may have some idea as
to how hard he would have to hit if he were dispensing with rotation. Of
course “a carry of 250 yards” is extremely long, and is rarely if ever
done in the absence of a helping wind from behind, but the Professor had
just been speaking of the practicability of such a carry “in still air.”
Even though it be abnormal, the vast disparity between an initial speed
of the ball of 350 feet per second and one of 1120 feet will make the
point clear.