The Hawaiian gazette., 1868-10-21
The Measured VILE.

er will drive her. Ii Is very evident that
the dozen people standing about the deck
are neither German tailors going to spend
holiday at hone. nor English tourists
bound for the Fiords and the Dovrefeld
if 50. they would be less interested in the
Fi.rfssp-FlSi. and more in the barge she
has lust missed running into. Two or three
Of them are eonversing with the pilot; one
IS talking 10 the man at the wheel about
the steering qualities Of the ship; another
Is specially interested in certain dials, just
above the engines. which Indicate the pres
sure Of steam snd other particulars Of
Ike character; and few others are look
ing over the bow. and carefully noticing
the shape AID size Of the waves which the
steamer throws of as she plo1ghs through
the still water The Flying Fish is bound
for the Measured Mile" at the Lower
Hope. reach or bend 81 the river lew
miles below Grayesend. there to try her
capabilities IN the way OF speed.
VIII she. or Will she not. average the
twelve knots an hour that have been con-
traeted fors The engineer Of the firm
which has built both vessel and engines
confidently predicts thirteen At the very
least be knows that, making fair dsdue-
ton for the tide. she is doing that now !;
how easily she overlook and passed that
empty Screw-eolier Just nowl But as we
get near the background. be thinks he IS
wanted below. and as he deseends the
steep iron ladder to the stoke-hole. one Of
the directors Of the company, who is evil
IDENTIFY well up in such matters, maliciously
remarks that be has gone 10 do the spur
ring business. A careful management Of
the furnaces, so as 10 get the greatest
quantity Of steam that the boilers can pro-
duce. Just as We begin the mile, is most
important condition Of success. But we
are close to the trial ground and the pilot,
by means Of 3 great bunch Of seals and a
strong steel chain. having hauled up an
enormous watch from the depths Of fob
pocket, we follow his example and all pro-
dUce our watches. There are the two
posts which mark the beginning Of the
mile; one is on the bank Of the river. and
the other some three hundred yards inland.
When the inland post appears to Us exact
" behind the other, that Is. when the Fly
fRg-FiSh and the TWO posts are in straight
line. the mile bagins. As we 90 on, the
posts appear rapidly 10 approach each 9TH
er. and one OF our party who has stationed
himself forward, begins, and all join in the
shout, Now" On we go, at s splendid
pace; the long waves Gu each side swell
higher and higher, and fountain rises on
each side of the ships eutwater, and falls
in such giistening drops SIS only the briny
element can produce Another shout in
dicates that the posts which mark the low
er boundary are past, and all compare notes
about the time Ii is settled at four min
utss five seconds, which gives a speed of
over fourteen and half knots per hour
for the first run with the tide. The time
of running one mile is readily converted
into rste per hour by table in which for
every five seconds is given the correspond
ing rate per hour.
We run down shout q mile below the
point and then turn round, and prepare for
running mile against tide. This mile, of
course, takes muCk longer than the other;
but the mean Of the two Is taken as the
speed of the ship, independent of the tide.
Five runs are made, and the four rates
obtained by taking the mean of the first
and second. of the second and third. the
third ard fourth. and the fourth and fifth
are added together and divided by four, TO
obtain the true mean speed Of the ship.
But, it may be said. why not have an even
number of runs, and taking the mean of
them, so get mean speed. This would
not give a true result, because the force Of
the tide is so continually varying that even
the loss by one run against the tide does
not exactly represent the gain By the run
with the tide Immediately preceding it.
Nor is this the only consideration in the
matter, for false mean speed may be obtain
ed by skilful pilot steering the ship in the
full force of the tide when running with it,
and in slack part of the stream when run
ming against it. This little piece of trick
cry Is often Praeticed upon unwsry ship
owners. Of course, to get true result, it
Is necessary that the ship shall run in a
straight line exactly at right angles to the
straight lines defined by the posts-that is,
the least distance between them. If she
vary from this course, she has to run more
than the mile; but as any error in this d.
rectiOn tells sgainst the builder, il Is always
carefully provided against. We have now
to make our runs at balfboiler power, and
the result is, that when the ship parts with
half Of her propelling power, she only loses
one-fourth Of her speed; indeed, it is often
observed that the last knot or two costs
more coal than all the rest of the speed.
A ship Of the royal navy-a fast ship of
her class-in recent trial, only lost ten
per cent of her speed when half was sub
stituted for full-boiler power.
The trials Of ships Of the royal navy take
place at Stokes Bay, near Portsmouth, and
at the Malpiu Sand. at the mouth of the
Thames. Large "Reminiscences are al
so tried at the Malpin. there being great
eE depth Of water and more room to turn
than at the Lower Hope. Many objections
have been made Of late by naval men to
the system Of trying ships at the measured
mile 1t Is said that ships speed at the
measured mile in smooth water is of no
use as criterion Of her speed at sea and
that ship never does so much on any fu-
ture occasion as at the trial On the other
hand, it Is said that trials at the measured
mile ara the ouly method Of comparing
ships with one another. Each ship Is tried
under precisely the same conditions
smooth water. the tide eliminated from
the question, and each engineer, for his
own credit, provides the best coal and the
best stOkers- Thus, as the trial gives rs
not the ordinary, bat the maximum speed
that can De got out Of q ship, il Is useful
to Be able TO compare the maximum speed
Of ships; indeed. it Is almost impossible
to compare speed in any other way, for in
what are called dssp-ssa trials We can new
er be sure Of having the same conditions
in any two successive trials, not even in