The Sun.
London, England, 1856-08-16 00:00:00

if he does possess the best ships, it is equally his interest to I
keep th it fact, and the means of acquiring them, to himself,
so that the charges for freight may zontinue to be ruled by
the inferior dynamic qualities of the average ships employed
by the trade, not by the superior dynamic qualities of the '
best ships as possessed by himself, the difference being the
shipowner's private advant age or thepublic'sloss. It is there-
fore the interestof the public that all bad typesof shipping be
exposed and eradicated. Freight would then, as respects the
quality of ships, be ruled by a scale of charges derived from
the performance of a generally improved type of ships
working in fair competition with each other. Having al-
reedy defined the measurement of the units by which we
propose to designate the working power of the engines and
the size of the ship—namely, ind. h.p. at 33,0001b5.,
raised one foot high par minute, and tons weight of dis-
c placement at 35 cubic feet of water to the ton, it is now
necessary that we refer to the received law or formula by
which the comparative dynamic duty of steam-ships may
be numerically ascertained. The formula usually adopted
for obtaining the co-efficient of dynamic duty of steam-
ships is { 17.3 C in which Dis the displace-
Ind. h.p.
meut of the ship at the time of trial, expressed in tons
weight, V the speed (usually expressed in nautical miles
per hour), and ind. h.p. the working power as escor-
t tined by means of the indicator. The resultant number
C deduced from this formula is termed the co-efficient of
dynamic performance, This co-efficient C will be a con-
stant number for all vessels of perfectly similar model or
type of form, and of which the engines are equally effective
in proportion to their gross ind. h.p. ; but if the vessels
be not of similar type, and the engines not equally effec-
tive in proportioh to their ind. h.p., the co-efficient C will
vary, and thus the dynamic performance of different ves-
sels will be comparatively clee slued. It is not our purpose
in this paper to raise any question as to the scientific ra-
tionale or resultant accuracy of this formula; I will merely
observe that though open to criticism in several respects,
the results of experience have demonstrated that this for-
mula, when applied to any known type of ship, expounds
the mutual relations of displacement, power, and speed,
with a degree of precision that admits of its being practi-
cally made use of for determining the resultant speed that
is to be expected from any combination of power and dis-
placement ; and in like manner any one of the three ele-
ments of the formula may be deduced from the other
two being given. Further, this formula may be rendered
available as a counting-house check on the working opera-
tion of steam-shis simply by substituting the con-
sumption of coals, expressed in cwts., per day of 21
hours (W), in lieu of the ind. h.p. ; for 1 cwt., or 11flbs.,
per day of 24 hours is at the rate of 4.661h5. per hour,
which is probably about the ordinary consumption per ind.
h.p. per hour, and it ought not to be exceeded. If, there-
fore, in lieu of the ind. h.p. we substitute the consumption
of coals, calculated in cwts. per day of 21 hours, the re-
sultant co-efficient (C) will afford an approximate indica-
tion of the good or bad performance of ships, as compared
one with another; and the fact of an inferior performance
being thus detected, the cause to which it may be attri-
butable, whether to inferior type of form or foulness •f
bottom, or inferior adaptation of engine, or inferior con•
struction of boiler, or inferior management on board ship,
will then become the subject of professional inquiry; thus,
the merchant, by aid of his counting-house statistics of
displacement, time on passage at given length, and coals
consumed, will be enabled to detect the fact of inefficiency,
and it will then be for the professional engineer to detect
and remedy the cause thereof. The annunciation of the
formula, or the mercantile rule above referred to, is as
follows :—Multiply the cube of the speed, expressed in
knots or nautical miles per hour (V 3), by the cube root of
the square of the displacement (D2-3),and divide by the
consumption of coals, expressed in cwts. per day of 21
hours, the resultant numeral co-efficient (C) will indicate
the dynamic or locomotive efficiency of tie? vessel ; and
such is the variable condition of steam-ships in present
use, that the co-efficient has been found to be as low in
some cases as 120, whilst in other cases it has reached the
number 250. The pecuniary value of gold is determined by
assay ; and in like manner the contract price to be paid for
a steam-ship should, in some measure, be regulated by the
co-efficient, based on the mutual relation of displacement,
speed, and coals, which may be realised on trial of the ship ;
for example, multiply the contract price by the numeral co-
efficient that may be actually realised, and divide by the
co-efficient that may be regarded as the par measure of
dynamic efficiency, according as the vessels may be painted
or sheathed with copper. Contracts based on this principle
would constitute a check upon the production of inefficient
ships, and award a premium on the construction of ships
of superior merit. The approximate trustworthiness of
the formula V 3 D
—C being conceded, we now
Ind. h.p.
have the means of pursuing our exposition of the extent
to which any definite difference of type or falling off in the
working condition of a ship will affect the amount of prime
cost expenses incurred in the conveyance of merchandise
by steam-ships—suppose, for example, that we have ships
whose coefficients of dynamic duty or index numbers (C)
V 4
h. p
deduced from the formula {lnd. s _0 } are respec-
tively. 250 and 166, which numbers correspond with 1,000
and 664, if the unit of marine engine-power be taken at
4 ind. h.p., as is the case in the tabular calculations given
in Atherton's " Steam-ship Capability," and are co-effi-
cients of dynamic duty not unusual as between different
steam-ships in actual practice ; in evidence of which, con-
firmatory of the official records whence these numbers are
taken, I may refer to a tabular statement of steam-ship
trials recently supplied to me by one of our most expe-
rienced firms (engineers and shipbuilders), by which state-
ment it appears that, adopting the formula referred to, the
index numbers or co-efficients of dynamic duty of eight
steam-ships varied from 251 to 149—thus showing that the
difference of constructive types now assumed as the base of
calculation for this exposition is not an exaggeration, but
such as is common in practice. In the first place, referring
to " Steam-ship Capability," 2d edit., p. 78, we will expose
the difference of power (Ind. h.p.) which would be required
by two vessels, A and B, of the respective types or working
conditions of service indicated by the co-efficients above
referred to (namely, 250 and 166), supposing the vessels to
be each of 2,500 tons load displacement. The vessel A will
be propelled at 8 knots, 10 knots, and 12 knots per hour, by
376 ind. h. p., 736 ind. h. p., and 1,272 incl. h. p.; but
the vessel B will require, to attain the same rate of speed,
568 incl. h. p., 1,112 ind. h. p., and 1,920 ind. h. p. Thus
the ship B requires, in consequence of her inferiority of
working condition, or type of construction, an increase of
power of no less than 50 per cent. in order to attain the
same rate of speed as ship A ; and, be it observed, that
these assumed co-efficients are within the range of ordi-
nary difference between one ship and another. We will
now show the sacrifice which such a difference of type pro-
duces in the weight of cargo which these ships of (say)
2,500 tons displacement, with mean quantity of coal ou
board, would respectively carry on a given passage, if
powered for running at the speed of 8, 10, and 12 knots
per hour. For this exposition we will assume the weight
of the ships themselves, as measured by the light displace-
ment of ships, when ready to receive cargo and coal for
the voyage, to appropriate 1,000 tons displacement, being
4J per cent. of the load displacement. We will also assume
the weight of the engine department complete at 5 cwts.
per ind. h, p., and the consumption of coal to be at the
rate of 4lbs. per ind. h. p. per hour, and the length of pas-
sage, without re-coaling, to be 3,250 nautical miles, being
about the distance from Liverpool to New York or to
Constantinople. On these data, according as the vessels
may he powered, as before shown, for being propelled at
the speed of 8, 10, and 12 knots per hour, the displacement
available for cargo in A will be 1,270 tons, 1,103 tons,
and 875 tons weight of cargo; while in B it will be 1, ,52,90 U
and 556 tons weight. The consumption of coal in A. will
be 273 tons at 8 kuots, 467 tons at 10 knots, and 615 tons
at 12 knots; and in B it will be 412, 615, and 929 tons
weight. Hence it appears that purely in consequence of
the difference in constructive type, or waking condition
of the ships, the reduction of cargo in B, as compared with
A, will he 9, 18, and 36 per cent., according as the speed
may be 8, 10, or 12 knots per hour; while the increase of
coal, being in proportion to the increase of power, will in
each case be 50 per cent. But the public evils of an infs.-
rior type, or neglected condition of ships, will be still more
fully exposed and be more definitely understood by the
extra £ s. d. charge that must be made for freight per
ton weight of goods conveyed, in order to meet the
prime cost expense of conveyance. In order to work out
this calculation, we must assume certain data of investment
and current expense as constituting the prime cost charges
of permanently establishing and upholding a commercial
fleet of steam-ships; and as this is the vital point in which
the public, as consumers, have a direct interest, it will be
expected that I enter upon it in considerable detail, as set
forth in supplement to " Steam-ship Capability," 2d edit.,
page 76. In the first place I would remark that it is only
(luring the number of days that steamers are annually at
sea conveying cargoes of goods from port to port that they
earn the income that is to defray the whole annual expen-
diture incurred. The number of days per annum during
which steamers are at sea will, of course, depend materi-
ally on the service in which they may be employed ; and
as it is proposed to work out our calculations with refe-
rence to a passage of 3,250 nautical miles—such, for ex-
ample, as a passage from England to New York or the
Black Sea—l have assumed that the vessels employed on
such service may be at sea 210 days per annum, In the
next place the cost of coal is a very material item, greatly
dependent on the service on which the vessels may be em-
ployed. This I have assumed at 21. per ton weight as the
average cost of the yearly consumption. Next, as to the
ship : I have assumed that a ship of 2,500 to 3,000 tons
load displacement would be purchased from the builders
as a ship of about the same amount of tonnage, builders'
measurement, and that the cost of the ship, completely
fitted, equipped, and furnished in all respects ready for
sea, would be 251. per ton. Then, assuming the interest
on investment at Si. per cent. per annum, the upholding
and replacement at 10 per cent, per annum, insurance at 5
per cent. per annum, and wages and rations of officers and
crew all the year round at 31. per 100 tons per week. On
these data we shall have the nrinie cost expenses inciden-
tal to the hull amounting to 61. lls. 2d. per ton of tonnage
per annum, which is Bd. per day sea-time, assuming
the vessel to be at sea 200 clays per annum, exclusive
of harbour dues, lights, and pilotage, which are
supposed to be the same for all ships of equal ton-
nage. Next, as to the engine department. The ave•
rage price of marine condensing engines, as now usually
constructed, may be rated at 501. per nominal H.P., and
in general each H. P. nominal may be expected to work up
to 21 ind. h. p., so that the cost of marine engines may be
rated at 201. per ind. h, p. Then, assuming the interest on
investment at 5 per cent. per annum on the contract cost,
the upholding and replacement at 10 per cent., insurance 5
per cent., wages and rations of engineers and stokers at 5/.
per 100 ind. h. p. per week, consumable stores (coal ex-
cepted) 21. 103. per 100 ind. h. p. per week, on these data
we shall hsve the prime cost expenses incidental to the
engine department (exclusive of coal) amounting to 71.185.
per ind. h. p. per annum, which is 9J. per day per ind. h.
p. sea time, assuming the vessel to be at sea 200 days per
annum. These assumed data of pecuniary charges inci-
dental to steam-ship transport service, as applied to
mercantile purposes, combined with the mutual relations
of displacement, power, and speed, which are derivab!e
V 3 Di
from the foregoing formula{ ----=o}- according to
h.p.
the constructive type or locomotive quality of the ship,
as shown by the co-efficient or index number C, enable us
to make up the prime cost expenses, being the minimum at
which goods can be conveyed, and which therefore should
constitute the base of the estimate by which a minimum
scale of freight charges should be estimated ; and applying
these data to the ships A. and B, employed on a passage of
3,230 nautical miles, as exemplified in the supplement to
Atherton's "Steam-ship Capability," 2d edition, page 78,
the minimum scale of freight charges per ton of gnu s,
according as the vessels may be powered for a speed of 8,
10, or Ifknots per hour, will, on the data referred to, re-
quite to be as follows :-
8 knots. 10 knots. 12 knots.
Ship A..-- 15 7 £2 4 6 £3 4 6
Ship B 2 7 2 3 9 8 616 3
The proportions in which goods, according to their respec-
tive kinds, may be made to bear freight charges so as to
yield the average return per ton weight on the entire cargo
is altogether a matter of commercial discretion and manage-
ment. The entire cargo must be made to yield the aver-