The Sun.
London, England, 1854-04-14 00:00:00

INSTITUTION OF CIVIL ENGINEERS.

The discussion was taken on D. K. Clark's paper,
" On Ruthven's Propeller."
It was contended, that there was no novelty in the
system of propulsion proposed by Messrs. Ruthven.
Benjamin Franklin was among the first to notice it ; he
related, that as a boy, whilst bathing in a pool, into
which a wooden pump had been thrown, to swell the
timber, he got astride upon it, and commenced pumping;
to his astonishment he found that he was propelling
himself across the water subsequently he investigated
the circumstances, and-admitted the inefficient applica-
tion of power. Sir Isambard Brunel attempted propul-
sion by means of.a tube, in whioh there was a diaphragm,
pushing the water before it, and acting upon a very light
valve on the return stroke ; this was only an elongated
paddle-wheel with an intermittent and inefficient action.
Mr. Bidder tried the system also, on board a canal
boat, and although quite aware of the loss of power in-
cidental to it, he expected a compensation from the ad-
vantageous application of steam, as opposed to animal
power.
As to this particular case of Ruthven's and other simi-
lar propellers, it was argued, that the reasoning in the
paper was as totally at variance with the actual results
of the experiments, as with the received laws of
hyd macs,
To shew this, it sufficed to state, that according to the
paper, the useful effect realised, was 64 per cent, of the
power of the engine, stated at 40 H.P. (indicated),
which would give 251 H.P. useful effect ; but it was
stated, in the experiments, that the two nozzles were 10
inches diameter each =together 1 1-12 square foot area.
The head of water was 8 6-10 feet= to a pressure of
nearly 5401b5, per foot, or to a total pressure of about
580 lbs., which represented, also, the resistance of the
vessel at 91 miles per hour, giving, therefore, a useful
effect of 14f H.P., instead of 251 H.P.,. as stated in the
paper.
It was an error to state, that the maximum of useful
effect was when the velocity of the issuing water was
equal to that of the vessel, or when the water dropped
vertically from the nozzles ; it could be shown, that in
that particular condition there was not any development
of useful effect. The actual operation of the system of
propulsion, was then shown to be analogous to the
assumed MO of a closed vessel of any shape, filled with
a fluid of given density, and under a given pressure ;
it was evident, that so long as the vessel remained in
that normal state, no propulsive force would be exerted
in any direction ; the whole being in equilibrio ; but on
an aperture being made in either of the sides of the
vessel, it was obvious, that the area of the opening,
being relieved from pressure, the equilibrium would be
disturbed, exactly by the extent of that aperture, into
the head, and there would be a corresponding force
exerted in the opposite direction.

To apply this to the case under consideration, a ves-
sel must be imagined, containing water under a pres-
sure = to 3 feet, which was the bead due to the velocity
of the vessel, in the experiment. By making an aperture
of about 34 feet area, there would be an unbalanced
pressure of about 580 lbs., equivalent to that of the for-
mer statement; but the velocity of issue would be 14
feet per second, and the power used would be about 15
H. P. But if the aperture was assumed to be reduced
to 1 1-12 square foot = the area of the two nozzles ;
then it would require 8 6-10ths feet head to produce the
same pressure. The velocity of issue would be 23 feet
per second, and the power would be about 25 H.P. ;
thus the power required was exactly in the ratio of the
velocity of issue, or inversely as the square root of the
head. The loss was therefore 60 per cent, instead of 12
per cent., as stated in the paper.
But the fundamental error in the paper was the omis-
sion of the loss of power arising from picking up the
water in a state of rest, and communicating it to the
velocity of the vessel. Supposing the water to be com-
posed of an infinite number of globules, possessing
weight, and being in a state of rest, they must all be
raised to the head due to the velocity of the vessel, and
then to the additional head requisite for propulsion.
In the present case the quantity of water issuing from
the nozzles was 25 feet per second ; this required to be
raised 3 feet, to be equivalent to the velocity of the ves-
sel—demanding, therefore, the exertion of 9 H.P. The
results of the experiments would be more correctly stated
thus :
Useful effect

14,1 H.P.

Power consumed in raising the water to the
velocity of the vessel
Power used in propelling the water through
the nozzles

25 H.P.

Total power expended, exclusive of the fric-
tion in the water-ways, and of the engine
itself
34 H.P.
The absence of indicator diagrams was regretted, as
tending to throw a doubt on the results ; but it was ad-
mitted that the boiler surface, and the actual consump-
tion of fuel, bore out the statements of the paper.
It was contended, in reply, that though engine power
was consumed in getting the water up to the speed of
the vessel, it did not necessarily follow that an equal
amount of power was further required to expel the water.
This single employment of power would be arrived at by
properly forming the water passages, so as to avoid all
concussions of the water, by rectangular bends, or by
sudden enlargements, or alterations of form ; and the
desired object was stated to be so to proportion the
dimensions of the engine and the propeller, that the
effluent speed of the water in one direction would be
equal to that of the vessel in the other. In this case it
was stated 100 per cent. of the engine power, minus
fractional resistance, would be usefully available.
That, practically, there were situations in which such
a propeller might be found very serviceable. For in-
stance, where paddle-wheels were objectionable, amidst
ice, and in shallow water, where the 'screw was not
available, and in ninny other situations, where any great
projections from the sides of the hull were undesirable.
As an example, it was stated that it would be very
desirable, for the purposes of the Fire Brigade, to have
the means of bringing up the large floating-engine at all
times of the tide and under all the circumstances of ice,
of an encumbered stream, or of shallow water, at a
speed of ten miles an hour, propelled by its own engines.
Experiments had already been made upon one of the
floating engines, which, although very imperfect, were
sufficient to prove the adaptability of the the system to
the wants of the Fire Brigade.
In fine, it was contended that although there still re-
mained much to be done to demonstrate the practical
efficiency of so great an innovation, the experiments
were sufficiently successful to induce further investi-
gations, and which the author was requested to
continue and to report to the institution.
Portions of the evenings of the 14th and 28th of March
were devoted to the discussion of Mr. Yates' paper,
"On the Advantages of Uniformity in European
Weights, Measures, and Coins."
Reference was made to the practical working of the
proposed change of the present currency, to the French
decimal system, and the numerous inconveniences to
which commerce would be subjected in the readjustment
of all dontracts, debts, exchanges, &c. The intricacy of
settling accounts would be infinite, and no correspond-
in.. advantage would result. The "franc" shown in
the scheme was not in reality equivalent to the French
coin of that denomination ; it was tenpence, and all the
other coins would be equally fictitious.
It was assumed that the first step towards fixing a
decimal system must be, the adjustment of the propor-
tional value of the present coins, and eventually of a
new issue ; a corresponding arrangement of the weights
and measures would soon follow. So many proportions
of systems had been published, that it seemed as if every
person who devoted attention to the subject, had tried
to invent a new scheme, rather than to devise the method
of arriving at a decimal system with the greatest facility
and the least derangement of the public convenience.
The following technical points were then considered
with regard to coins :-Ist. The standarsl of fineness ;
2d. The relation of coins to the denomination, or money
of account, of the country wherein they circulated ; and
3d. The metallic standard.
First. The standard of fineness depended on the quan-
tity of alloy introduced in the process of manufacture,
or coining. If this were identical in all countries, great
trouble would be avoided, but it was argued that prac-
tically such an accordance was scarcely attainable, and,
in fact, that a table of exchange values met the difficulty
of the present discordance.
Second. In order to show how difficult of attainment,
would be an assimilation and interchange of British
coins, with those of other countries, it was argued that
in the United States of America, where the currency was
practically based on a gold standard, the eagle, whose
value of 10 dollars, = about 21. ls. English, and the
half-eagle, =ll. Os. 6d., or very nearly the English sove-
reign, it would be necessary to raise one standard, or
to lower the other, in order to do away with the appa-
rent difference of 2t per cent, now existing, and this
would involve the remining of the whole circulation of
one, or the other country, at a certain and great ex-
pense, and at the imminent risk of complicating all ex-
isting pecuniary engagements. It was urged that the
scheme of assimilating the present coins to the French
franc, &c,, was equally fallacious ; in fact, that the new
franc would only be tenpence English, and not of the
exact value of a French franc, which equalled 94 pence,
and so on for the rest of the proposed series, thus show-
ing a real difference of 44 per cent., which was too
much to be sacrificed in mercantile or monetary tran-
sactions.

unit, inasmuch ag the various dollars of the several
The dollar was argued to be equally acsouthne.
tries, and even of the same country, had different
fvaluesfifty
fallacious,
and nob one of them possessed the precise value o
pence English, which had been assumed.
The case of the British North American colonies was
quoted, as an example of the confusion resulting from
the use of similar denominations of account, without
identity of value. The result being, that in no two colo-
nies did the nominal pound represent the same value.
Third. That which opposed the most serious obstacles
was the metallic standard ; there could be no real par of
exchange between countries without a previous agree-
ment as to adopting either a gold or a silver standard ;
because the relative value of the two metals was con-
stantly fluctuating. The discovery of gold in California
and in Australia, followed by an excessive demand for
silver, for the East, would probably produce great
changes ; even at this moment, gold was partially dis-
placing silver, as a standard in France, where there was
apparently in progress a change similar to that which
had taken place in the currency of this country, during
the last century, ending in the final adoption of a gold
standard in 1816 ; and it appeared very probable that
gold would become the standard in France, as it was
here. It was presumed that the advocates of the franc
did not mean to return -to a silver standard, as the
greatest confusion in the monetary system must be the

result.
The pound sterling being now admitted to represent
the value of the quantity of gold contained in a sove-
reign —all the shyer and copper coiaa being mere tokens,