West Virginia Democrat. [volume] (Charles Town, W. Va.) 1885-1890, 1888-06-29
TRACKING THE DEEP.
How Ships That Cross the Sea Find
Their Way From Point to Point.

we bIdttt oO hO''
that most ofus have special reasons
to be interested in the method by
which our safety in travelling is
cared for. Even those who do not
travel themselves, have generally
friends or relatives who travel, ami
even those who neither travel them
selves. nor have friends whe do, are
interested without single excep-
tion) in the system of commerce
which renders travelling necessary.
1t may truly be said that the price
Of every simple article OF food ana
clothing-even the home products
of agriculture or manufacture-de-
pends more or less on the particular
problem of travelling which Ii am to
consider now-fnding the way at
sea.
/ wonder how many passengers
on long sea journeys inquire how
tie ship which carries them is guild
ed on her course. Ny own exper-
ience suggests that not one passen-
ger in fifty. cares anything about it.
/ have often, when at sea, thought
what farce it is for so many peo-
pie to pretend to take interest in as
Economical researches about the po-
sition of the earth in her orbit, the
nature of other worlds, the relations
of other suns to ours, and the move
ments of our sun and his fellow SIMS
in space, when it would scarcely
ever be possible to get a score OF
persons together on board ship to
consider the corresponding prob
lens in regard to the ship and 9TH
ers travelling with her on the ocean,
though the lives of all the passen-
gers depend. on these problems be-
ing satisfactorily dealt with.
What erroneous ideas are enter
tanned on this subject is shown by
the way in which Charles Reade
pictures Penfold's efforts to ascer-
tain position of the island on which
he and HELEN Rolleston find refuge
after the scuttling ofthe Proserpine.
Reade probably knew more about
such matters than most persons not
professionally engaged in astronom-
ical research; and he was acquaint-
ed with naval men who could set
him right. l think some such
friends must have told him to omit
the account of Penfold's determina
tion of the ships position in an ear
lier chapter; rs | see this passage is
omitted in recent edition, though
reference to it in the correspond
ing island scene is left Yet he
represents Penfold as determining
the longitude approximately by a
method which would only have CIV
en- it roughly, and as foiled by the
difficulty of determining the latitude
(astronomically) though the very
observation he is supposed to have
made for the longitude, would have
given him the latitude much more
readily. Penfold makes q perfectly
ludicrous remark about the suns
parallax, "Now for some way OF ap-
proximating to the parallax =
which has nothing to do with the
problem of determining the place of
his island-if it had, he ought,
sine he is represented as knowing
most things, to have known the So
lar paralIax; or if he had forgotten
it and wanted it, he might, at least,
have remembered the suns distance
and the earth's diamater, whence
he could have determined the paral-
lax in five minutes. Isl
Finding the way at sea depends
on two methods, each OF which is
theoretically correct in itself-dead
reckoning and astronomical obser-
yation. As observation may be pre-
vented by thick weather, the second
method may fail throughout a voy-
age, or during the critical parts of
it when land is approached. Thus
dead reckoning, on which in many
cases the most scientific Captains
may have to trust, must be consid-
cred first. 4sIi.
Dead reckoning (why called
! dead" / do not know nor greatly
eare) depends on the determination,
hour by the ships motion, and the
determination of the direction and
velocity, thence of her position after
each days various movements. If
we know ships position at a given
time-say at noon on July l-and
she sails or steams at a known rate
in a determined direction for a Ger
tain time-an hour, say-we can
calculate her position at the end OF
that hour, subject to the action OF
currents. Since the rate and direc.
tion of currents are mostly known
we can take this particular cause Of
motion into. account. Thus we car
mark in on our chart the position o1
tile shiplat! the end of the hour. Sc
at the end of the next interval Of
time during which her course re