The morning news. [volume] (Savannah, Ga.) 1887-1900, 1896-11-25

Revenue Marine, of the French, American,
international, Portland and many other
large lines of steamers, as well as on
numerous merchant vessels, and have been
found indispensable by them.
The principle of the instrument Is that
1t shows by optical demonstration the
movements of the ship. and its relation 10
any point or object. 1t will demonstrate
in an instant any problem in trlanguia>
ton, which is the basis of every kind OF
navigation. Like almost all valuable in-
yentions, it is so simple that one wonders
why it was not inventend long before
1t was. 1t consists OF base about two
feet long, on which are placed two small
disks, one sliding in a groove eighteen
inches in length, and the other fixed at
one end of the groove. On each of the
disks is an arm eighteen inches long
which can be moved in any direction par
allel with the plane of the base. The
arms. and the sides of the groove, are d.
vided into inches and tenths of inches.
and with them, of course, a triangle of
any desired shape may be formed, with
all its side so divided. The disks on
which the arms are pivoted are divided
up into points and quarter points of the
compass and also into degrees. At the
point on which each arm is attached to
the disk, and on the end of each arm is a
dencate sight, and when these two are
brought to bear on an object it's bearing
from the ship is indicated by the point on
which the arm rests on the disk In get
ting ships position from an object on
the shore a sight is first taken from the
fixed eisl, and the arm is then fastened
IN position with clamp on the top of
disk. A short distance-three miles, for
instances then logged off, and the NOV
able disk is slid along the groove, which
| has been laid in the same direction as tho
snip course. for three inches, an inch
to the mile being the scale ordinarily used,
although for other problems any scale can
| be used by simply multiplying or diyid-
ing. Another sight is then taken over the
arm on the sliding disk, and this arm and
| DISK are clamped, and the whole problem
| is before the navigator. The two arms
| will, of course, cross each other, and the
| point of intersection represents the object.
The distance marked off by the intersec-
tion on the first arm represents the dis
lance of the first sight, the distance mark
| ed on the second arm represents the dis
lance of the vessel from the object at the
time of the second sight, and the distance
marked on the edge of the groove repre-
/ sents the distance sailed by the vessel.
| The whole thing is done simply by two
| sights and the clamping of two arms, and
| is actually demonstrated to the eye with
out the possibility of an error always
| brought in by the necessity of figuring
/ and measuring with dividers.
| An even more important use of the in
| strument is in determining where a yes
| sci VIII pass on given course in relation
| to any object. Suppose a captain is run
| ning up toward a point and wishes to
know how far off shore he will pass
| if he holds his course. He sights with the
arm on the fixed disk on some prominent
object on the end of the point, and then
/ finds his distance from the point on this
sight to be nine miles by the method
already described. He then sets the arm
on the movable disk at right angles to
| the groove, and slides the disk along
until the second arm intersects the first
at the nine-inch mark. The distance
marked off in the second arm will then
| be exactly the distance which his vessel
| will pass off shore. This calculation is
of great Importance, as it enables a cap
tam TO know to tenth of a mile where
he is going long before he gets there.
The possibility of placing a vessels po-
| sition exactly might be of great i'm
| portance in international complications.
| rake case which happened last winter
| to one of the Boston Fruit Companv's
| steamers, which, while coming round the
coast of Cuba on her way from Jamaica
was held up by a Spanish gunboat. If
the captain had had telemeter on board
he could have determined whether or not
he was inside the three-mile limit be.
tween the time that the gunboat signaled
him to stop and the time when she fired
the nrst gun, and could have gone ahead
| with perfectly clear knowledge of his
| rights. These instruments would also be
of great value to the American fisher
men to determine whether or not they
were within the three-mile limit, and
might save many arrests by the Canadian
| government.
The way in which dead reckoning IS
| worked out by the telemeter is slightly
different from the manner of determining
| distance by sights, although it is on ex-
| actly the same principle. The base of the
| instrument, instead of being placed on a
line with the course of the vessel is placed
east and west, and the arm on the fixed
disk is placed on line with her course
The arm on the movable disk is then
clamped at right angles with the groove
and slid along until it intersects the other
arm at the distance run by the vessel in
| day. The point at which the first arm
| is pivoted then represents the position
of the vessel at the sight of the day be.
fore, and the point of intersection Of the
two arms is her present position by dead
reckoning. The distance marked off or
the groove is the casting and westine
which the vessel has made, and the dis.
lance marked on the second arm is the
northing and southing which she has
made. In working out problem of this
kind the scale of an inch to a mile car
not be used, as the instrument is not large
enough to record a fun days run. But
if the vessel has run 300 miles inches are
marked off, and the results are multi.
piled by 100