The Portland daily press., 1896-06-13
SCIENCE AT SEA.
Some of the Things Naval Officers Have
to Know.

(Harry Fulton in New York Journal.)
The modern naval officer is required to
be more of scientist than seaman.
The application of the sciences aboard a
big ship Inns done away with the neces.
| sity for commissioned officers possessing
a practical and perfect knowledge of the
| mysteries Of reefing. handling and steer
ing The modern naval officer is OF
| necessity a splendid mathematician, an
| able meteorological, good electrician and
| competent engineer. This in addition
o the primal requirements of gunnery,
workmanship, courage and activity.
In navigating modern steel ship
many difficulties are incurred which do
not ell tor into the problem where wood
en- fabric is involved. Most of them grow
out of the multiplied vagaries of the COM
pass under the combined influences of
the steel in the ships hull and armament
the magnetic forces generated by the
motion of the propellers and shafts, and
the induction diffused by the ships cleo
trioal plant. Each of these causes adds
several varying degrees to the natural de-
Walton of the compass, and each must be
compensated for in some way. Thus the
compasses of a steel warship, after their
primal corrections for natural deviation,
must be corrected again to compensate
for the attraction welded by the Iongi-
tudinal steel and iron in the ship, the at
traction of the horizontal iron and the
differing degrees of attraction exercised
nv the oGco f chin boy
over in a seaway. These-only few Of
the variations to be considered-are COM
pensated for in several ways. The longi-
tudinal IRONS attraction is negatived ny
two balls of soft iron, adjusted on the
plane OF the compass card. That of the
horizontal iron is compensated for in an
adjustable tray of magnets carried in
the blnnacle underneath the compass
magnets. The angle OF list, or heel, and
consequent variation of the degree of at
traction by the ships mass. is compen
stated for, i believe, by steel rod run
ming vertically through the brass binna-
Gle stand. All these adjustments and
corrections are only temporary, for the
curve of deviation varies in different lat1-
tudes and in relation to tho curves of the
natural magnetic currents. Hence by
mathematical calculation Of infinitesi.
NAL exactltude these known and estlmat-
ed errors and vagaIles Of tbs "ioadstone
needle" are discounted, and the naval
officer usually comes much nearer to
knowing his exact position than is COM
pretended in the assertion of an eminent
authority that 'the average nrror Of
marine computation Of position is 8. 6
miles,
The errors of thermometers in any sort
Of ships are yexing matters until long
record of the daily and hourly perform
ance OF each chronometer under varying
conditions of temperature and climate
enable close estimation of probable per-
formance to be made. Even then she
modern naval navigator uses no less than
three chronometers, the daily gain or loss
Of each b7 Greenwich time being as fire.
quently figured as possible, and the daily
reckoning being figured on the mean
MISUNDERSTANDING less than one-tentb
of a second-of the three.
So closely are these thermometers
watched that a thermometer is keut ia
the case and variations of temperatures
are taken into account in figuring their
deviation. And though chronometor
will run month or so, they Eare wound
precisely at o'clock every morning. and
so irp pnrtanU is this prompt winding es-
timated that it is daily reported to the
captain or commanding officer. In gun