Johnstown weekly Democrat. (Johnstown, Cambria County, Pa.) 1889-1916, 1890-03-21

not as appreciable. Existing guns, in
the hands of gun captains of fair skill,
will put about onefourth the shots fired
from them when ahoat into a target
twelve feet high and of most any length
the vertical rather than the horizontal
being the chief consideration--when at
1900 yards range, the distance being
accurately known. This will probably
be the effective range for opening future
engagements
Such is Mt least the opinion held by
most gunnery experts both in this coun-
try and in foreign services. 1t is to over
! come this element of uncertainty in the
! calculation OF the distance the enemy is
off, and to thereby increase the range at
which.the gunreigns supreme, that Lieut..
Fiske, United States navy, has brought
his knowledge and ingenuity to bear.
| His range finder, which is illustrated by
| the accompanying cut, introduces cleo
tricity and depends almost entirely upon
the principles OF the Wheatstone bridge
or the electrical balance. The instru-
| ment consists of an iron tripod support
ing flat iron table, carrying a telescope
which has vertical and horizontal mo-
ton, and which is also in the circuit of an
electric current. In order to secure hav-
ing base line, no matter whether the
vessel presents bow, stern or broadside
to the target, there are four of these tri-
pods on each ship, one at either end of
the bridge forming the shorter base line;
a third forward and fourth aft, form
i1rr lDncrpr hpya lin. inl, Al.
length of the ship.
The two tripods forming the base lines
are connected with the electric battery,
carrying weak current, two accumula-
tor cells being sufficient, and also with
galvanometer. The principle involved
in finding the range and position of an
object depends upon the determination
of fractional portion of n conducting
body bearing in length ratio to an angle
between two lines of sight directed upon
the distant object, and the measurement
of the electrical resistance of that length.
The practical working of the apparatus
includes three observers. one at each
telescope, and third at the galvanom-
eter. On topof one of the tripods, and
underneath the telescope, is slider
which is adjustable and has its middle
portion insulated so that the current can
not pass across, but goes by wire to the
galvanometer. Moving this slider one
way or another increases or lessons the
resistance and causes a DETECTION in the
needle of the galvanometcr
One of the observers sights his tele-
scope at the target, and q certain denec-
ton Of the needle is observed. The other
observer also sights on the object, and
the needle shows a change in DETECTION.
The slider is then moved until theneedle
Of the galvanometer reads zero, and the
position Of the slider in reference to a
liked scale of yards shows at once the
distance the target is away from the OBJ
ject. Well known principles of the re-
latiou of arcs and the sides and angles Of
triangIes bear TO each other render it
possible, from the data Of lengths. angles,
etc, Of the apparatus itself to extend
their proportions to any distance, and it !
is by these methods of proportion and
the electric balance that the required
distance is obtained. Its application is
not confined TO vessels alone, as it can
be applied anywhere where base line
Of known length can be obtained
For instance, the telescopes, suitably
mounted, could be sent out on the skir-
mish line or to any other advanced DO
sition and the distance of an cnemy's
works or troops accurately determined,
so that the gunners would know at what
range to elevate their guns. The trouble
on shipbourd las been that the base line
has heretofore proved too short for prac.
tical use, and the delay has been caused
by time required for communication be-
tween the two observers.