The morning news. [volume] (Savannah, Ga.) 1887-1900, 1900-04-04
AIM WITH BOTH YOUR EYES.
Errors of the One-Eyed sGuint-Thc
"Master Eye" Theory Condemned.

Errors of the One-Eyed Squint-Thc
"Master Eye" Theory Condemned.
Letter to the Editor of the London Times.
The correspondence on this subject
which has lately appeared in your col
umns does not appear TO me fully to clue
idate the facts or conditions of the prob
lem, which 1 should like to state from the
point of view in which they present them
selves to me. / Will take the ordinary
case of a young adult possessing two
sound and equal eyes of good or normal
vision, neither of which requires a glass
or would be assisted by one; such a per-
son, in short. would be eligible for
commission in the royal navy. The TWO
eyes are globes which move more or less
in unison with one another, and each
moves by rotation about fixed center.
The movements are effected by the CON
traction of the muscles appropriate to
each; and these muscles consist of six
pairs attached TO the outer tunics of the
eye and inserted into the bones of The
skull The stimulus to movements is fur
nished by the presence Of an objeLt Of
vision, toward which enc or both eyes may
be turned tor the purpose OF seeing il
clearly A straight line drawn from the
object of vision to the posterior pole, or
! axis of vision" of that eye. As the CEN
ters of the eyes are about two and a half
inches apart ii is manifest that the two
axis of vision can never be cOincident.
They form ,he sides of an isosceles, tri-
angle, The apex Of which is at the object
of vision, while The base is formed by an
imaginary line uniting the posi- erior poles
of the two eyes. When the two eyes are
directed toward an infinitely distant OBJ
tect such as a fixed star, the apex of the
triangle is infinitely distant, and its sides,
for all practical purposes, are parallel.
When the eyes are directed toward near
object, such as "a spot on a piece of paper
al a distance of twelve inches, the apex
of the triangle is on the spot, and its sides
are decidedly convergent The possible
movements of the eyes are numerous and
complicated but it is sufficient for the
present purpose TO think only of those
which change the directions of the axes
of vision from paralle!ism to conveyance,
or vice versa. The parallelism may be re-
garded as a state of approximate rest or
equilibrium; the conveyance as a state Of
activity, called into existence for the sake
of obtaining that fusion" or combination,
of the two visual images, by which our
ideas of relief or solidity are formed, and
by which our instructive judgments with
regard 10 the magnitude. the distanoe and
che position of the object are mainly
guided.
In taking steady aim with a rife at a
fixed object the vision is of necessity mo-
nocular. The barrel Of the rife, with it's
two sights, must coincide accurately with
the axis of vision of one eye, and can
not by any possibility coincide with the
axes of both, because they never coin
eide with one another. Such aim may
be taken from the right shoulder with
the right eye, or may be taken with the
left eye from the left shoulder or from
the right shoulder by means of a bent
stock; but it cannot be taken with both
eyes at once. The non-aiming eye may
be open or shut, but the image which IL
receives should make no impression upon
the consciousness, and should take no
share in the direction OF the weapon.
Firing from the right shoulder, in the or
binary way, 1t is easy, whether the left