Evening star. [volume] (Washington, D.C.) 1854-1972, 1925-02-19
Rotorship Idea Old.
Writer Tells of Principle Being
Applied by Briton.

To the Editor of The Star:
A recent issue Of The Star contain
ed an article from the North Ameri-
can Newspaper Alliance, entitled
principle of Rotorship' Power Like
the Force That Curves Ball." in which
it is claimed that the law governing
that phenomenon was first stated by
one Heinrich Gustav Magnus OF Ber-
lin.
So far as the application of that
principle to rotating cylinder is
concerned, Magnus is probably enti-
tied to that credit. But the general
principle has been known for time
immemorial, and was described by
Benjamin Robins, an English mathe-
matician, in volume l. pages $50, 197,
etc. Of his principle of Gunnery,
published about 1745. more than SO
years before Magnus was born.
I. The studies and experiments OF
Robins in that respect were confned
to spheres, especially to spherical
cannon and musket balls, as cylin-
dricai or elongated projectiles for
rifles were not then in common use, II
they had been then devised at all
1t was the common practice then to
use in rifles leaden spheres a little
larger than the bore Of the gun, and
to drive them down the bore with
rammer, SO that their outer surface
would be pressed into the rifins
grooves and cause them, when elected
from the gun, to revolye on. an axis
parallel to their line of flight. With
out that revolving 1t was impossible
to foretell in what direction the angie
of rotation would be, SO that the
spherical bullet whose lateral dlrec-
ton of rotation was not controlled by
the rifiing of the gun was liable to
curve upward or downward, or side
wise or at an angle, and so shorten
its. fight. This principle was fully
described and demonstrated by many
ingenious experiments by Robins.
The difference between the phe-
nomnenon as related to a sphere and
to a cylinder is only one OF Application.
1t is the same in principle, which is
that an object revolving against q
fluid or air current, whether that cur
rent be like a wind or water current
or be induced by the progress of the
revolving object through the sur,
rounding medium. will be subjected
to a dominating friction and pressure
on some distinct part of its surface
that will divert it from the line OF
its departure. If, as in case of a ship.
the revolving appliance is. attached
to a base that the applied force can
not divert in the line Of that force, 1t
will move in the line of least resist
ance, which in boat is lengthwise.
But conceding that Magnus discov-
cred that principle by his own refiec-
ton on the subject, and not from
having read Robins discussions, it
would only be another illustration of
the fact that the vast universe OF
mind sometimes tmanifests itself by
the intuitional development of ideas
of similar kind in different indi-
viduals.
If any one is entitled to the dis
tinction of first discovering and pub
fishing the underlying principles Of
the phenomenon above mentioned 1t
is Robins.
There are other phenomena related
to the principle mentioned, which nei-
Their Robins nor Magnus seem to have
apprehended, as that principle is at
the basis of many gyroscopic mani
festations and probably, OF, all of
them, including the problems OF; ord
nance ballistics. :.
WILLIAM TINDALL.