The Sun.
London, England, 1867-08-16 00:00:00

Lord Palmerston on Gunnery.

The following letter, written by Lord Palmerston
ten years ago in the midst of his numberless avoca-
tions as Prime Minister, affords so remarkable an
illustration of the activity of his mind and of the
prompt, vigorous grasp which he was capable of
taking of matters of scientific interest that it seems
well worth preserving. The letter was submitted
for opinion by Lord Pa,nmure to the officer whom
he usually consulted at that period lon subjects of

gunnery, with the following characteristic note :
" My dear —,—Read and inform me on the ab-
struse philosophy of our Prime -Minister ; I wonder
where we are to find a circular range of a mile
radius.—PANMURE." Lord Palmerston's letter is
as follows :--" December 20, 1857. My dear Pan-
mure,—There is an investigation which it would

be important and at the same time easy to make,
and that is whether the rotation of the earth on its
axis has any effect on the curve of a cannon ball in
its flight. One should suppose that it has, and that
while the cannon ball is flying in the air, impelled
by the gun-powder in a straight line from the can-
non's mouth, the ball would not follow the rotation
of the earth in the same manner which it would do

if lying at rest on the earth's surface. If this be so,
a ball fired in the meridianal direction, that is to
say, due north or due south, ought to deviate to the
west of the object at which it was aimed, because
during the time of flight that object will have gone
to the east somewhat faster than the cannon will

have done. In like manner a ball fired due eas
ought to fly less far upon the earth's surface than a
ball fired due west, the charges being equal, the
elevation the same, and the atmosphere perfectly
still. It must be remembered, however, that the
ball even after it has left the cannon's mouth will
retain the motion from west to cast which it had
before received by the rotation of the earth on whose
surface it was, and it is possible therefore that ex-
cept at very long ranges the deviation above men-
tioned may in practice turn out to be very small,
and not deserving the attention of an artilleryman.
The trial might be easily made in any place in
which a free circle of a mile or more radius could
be obtained ; and a cannon placed in the centre of
that circle, and fired alternately north, south, east,
and west, with equal charges, would afford the
means of ascertaining whether each shot flew the
same distance or not.—Yours sincerely, PALMER-
STON." It has been ascertained that the rotation of
the earth produces a sensible effect on the oscillat-
ing pendulum. The error into which Lord Palmer-
ston fell of supposing that the deviation of a ball
fired due north or south would invariably be wes•
terly will not escape notice. The deviation due to
the earth's rotation is of course different in each
hemisphere. In the northern hemisphere the devia-
tion is alwa3 s to the right of the gun, in the southern
hemisphere it is always to the left. Thus the de-
viation of a gun fired north in the northern hemis-
phere is east ; when firing south it is west ; when
the practice takes place in the southern hemisphere
it is west in a shot travelling north, and east in a
shot travelling south. The subject is one which has
often engaged the attention of philosophers, to whom
it has more interest than it can ever possess for prac-
tical men ; for so many corrections have to be applied
and the error is in itself so small that the deviation
of projectiles due to cosmical causes may well be
disregarded, and the experiments which Lord Pal-
merston suggested were never instituted. But Lord
Palmerston's letter possesses an interest quite inde-
pendent of its practical value, and has been pub-
lished by Lord Dalhousie's permission in the current
number of the Proceedings of the loyal Artillery
lnstitution.—Pall-Mall Gazette.