The Sun.
London, England, 1854-05-11 00:00:00

INSTITUTION OF CIVIL ENGINEERS.

The discussion being resumed on Mr. D. K. Clark's
"Description of the Deep-sea Fishing Steamer Enter-
prise, with Ruthven's Propeller ;" in allusion to the
former experiments, it was shown that the power re-
quired for the propulsion of the Enterprise, at 91 miles
per hour, was 35 indicated H. P., as estimated by Bourne's
formula for resistance, founded on the results obtained by
the Rattler ; this power was nearly what was stated in
the paper (40 H. P.), with which, also, the stated
consumption of fuel was in accordance. It was argued,
with respect to the supposed loss of power, -in com-
municating to the water the velocity of the vessel, that,
inasmuch as the action of the propeller was in principle
the same as if the intercepted water was raised to the
height due to the velocity imparted to it the velocity
was only lent to the water, and ready, in vinme of that
head, to be refunded when required ; and that the neces-
sary engine-power was equal to that which could raise
the quantity of water, required for propulizion, from
the level of the sea to the height due to the velocity
of efflux. On these principles, it was calculated, from
the data contained in the paper, that in the manage-
irent of the water, exclusive of all fractional resistance,
the ratio of power to effect was :
The power used=l22B H.P.
Ditto wasted =3 94 do.

Total l6 22 do.

and it was concluded that there was much to be said in
favour of Ruthven's mode of propulsion. The state-
ments as to the former experiinents were reiterated, viz.,
that the power required to communicate velocity to the
water, passed through the propeller, was not utilised.
For, assuming a ball to be suspended over the vessel, at
a height due to the velocity of the vessel, and moving at
the same rate, it was urged, that to raise the ball to.that
height and to communicate to it the velocity, would ob-
viously require just double the power necessary to raise
it. Assuming the ball to be detached, it would descend
vertically, as regarded the vessel, and would act upon it
precisely as it would it both the ball and the vessel were
at rest ; and as a consequence, therefore, it would only
act with the effect due to the height from which it
fell. As another illustration, it was assumed that
the deck of a vessel was level with the surface of the sur-
rounding medium, and that a given portion of fluid was
transferred from the medium to the level of the deck ;
then a certain amount of power would be expended in
changing the condition of the water and imparting to it
the velocity of the vessel ; but as this water would only
be at the level of the surrounding medium, it would not
flow out again, and the power that had been absorbed
would not again be utilized. It was contended that the
inference from the experiments quoted, viz., that the pres-
sure was double the hydraulic height due to the velocity,
was incorrect ; for the pressure was measured upon the
reduced section of the " vena contracts," which was only
-ths of the area of the real aperture, upon which area, as
had been shown, the unbalanced pressure should be esti-
mated ; and it was contended that the contrary inference
led to inconsistent and anomalous results. But in no
respect did these experiments apply to the case of water
passing through a tube, or pipe, beyond the " vena con-
tracts," as the area of unbalanced pressure would thee
be immediately reduced. Referring to the experiment
quoted in the paper, and assuming the possibility of the
reaction pressure being equal to double the height due
to the velocity, viz., 23 feet per second, i.e., =8 6-10ths
feet, then double that would be 17 2.106hs feet+ 9-10ths
foot (the height of the issue above the sea) would give a
total height of 18 I.loth feet; this x 25 feet (the quan-
tity of water per second) and x into 60 (seconds per mi-
nute) and ÷. 528 feet (the quantity of water raised one
foot high per minute, per horse power) gave 51
then adding to that the loss from the friction of
the water in the passages, as stated in the paper, to-
gether with the friction f the engine itself, it would
appear that the power applied must have been =-- 80
H. P., instead of 40 H. P. as stated,
,thus showing
that the experiment and the inference could not be
reconciled. Again, it was argued that the useful
effect was exprtssible simply by the difference of the
power consumed in giving to the water the speed of
the vessel and the power in expelling it ; that in the
admission and in the expulsion of the water, re-acting
pressures, measured by twice the head due to the
velocities of admission and expulsion, were exerted
longitudinally upon the vessel, the difference of these
reacting pressures expressing the useful effect. Pu t-
ting V for the speed of the boat, and V' for the
effluent velocity of the water, with respect to the
nozzles from which it is issued, then, the power ex-
pended being taken as unity, the useful effect was found
to be represented by _ _

Vi-V
2 V--
V'2

which showed, that when the forward speed of the vessel
and the effluent speed of the water were equal, there was
no useful effect; and that the maximum useful effect was
obtained, when the effluent speed of the water was twice
the speed of the vessel, and when the useful effect was
just one-half of the power expended, exclusive of the
friction resistance. Whereas, with the paddle, or the
screw, there did not appear, theoretically, any limit to
the ratio of the efficiency- —it might be equal to the
power—and in practice it.was limited only by the extent
of surface which it was convenient to give to the pad-
dle-board, or to the screw. Still, the amount of power
obtained by the jet was less affected by the deviations
front the most useful velocity than in the case of the
paddle or the screw ; and there might be found to be
practical advantages which would render the plan of
the jet very advantageous in numerous chases. With
respect to the unbalanced pressure of re-action, by the
flow of water through the side of a vessel at rest, it was
argued that all attempts to explain the subject by refe-
rence to hydrostatic principles were fallacious, and that
experiment alone could determine the results. Whitelaw,
in account of the re-action water-mill, had shown, by
experiment, that the re-action was measured by the
weight of a column of water of twice the head, when
the orifices were at rest. A recent experiment on
the re-action pressure was ale) described. A cylinder
was fitted with a jet pipe in the side, at the bottom, of
the form of the " vena contracta." It was suspended
from a considerable height, so as to hang freely, and was
filled with water, which was kept up to a constant level ;
when the water was permitted to flow out freely, an
unbalanced pressure of once and a half the hydrostatic
pressure under that head was indicated on a balance,
applied against the opposite side, as measured on
the small section of the " vena contracta." With re
spect to the formula, showing that the maximum
useful effect was only half the power expended, it
was considered that the conditions of ~the formula
did not meet the case of the propeller, for it was
assumed that the engine-power was available only for
expelling the water, and that the mass of the vessel
necessarily discharged the duty of taking up the water,
Now, the facts were stated to be, that the machine not
only discharged the water, but it also previously drew it
into the vessel by exhaustion ; and it was contended
that, under these circumstances, the maximum effect
was obtained, when the speed of the vessel was equal to
that of the effluent water, and amounted to 100 per cent.
of the engine•power, minus friction resistances. In fine,
though much difference of opinion was expressed as to
the mode of action and the economy of Ruthven's pro-
peller, it was agreed that in numerous situations the new
propeller might be found to possess practical advantages
over the paddle and the screw, and that the subject de-
manded further inquiry and investigation, theoretically
and experimentally.

THE NEW NOVEL, " AUBREY," BY THE AUTHOR OF
"EMILIA WYNDHAM."—This is another charming fiction
from, the pen of the delightful authoress of ' Emilia
Wyndham' and 'Two Old Men's Tales'—one of the
most popular writers of the day. In this new essay of
her powers the 'authoress has outdone all her former
attempts. 'Aubrey' abounds with delightful pictures
of family life. The heroine is a most loveable character,
and one that will win the admiration of all readers. The
male personages are more than usually attractive, and
the whole story displays considerable power and evinces
great knowledge of character. We confidently predict
a very extensive circulation for ' Aubrey,' and we are
assured that few readers will lay the book down without
receiving abundant satisfaction and delight from the
perusal of it."—Messenger.
NORWEGIAN TRUNK RAILWAY.—The length of this,
line is 36 miles ; capital 450.0001., of which the Noy-
wegian Government furnish one half, leaving a capital
of 225,0001. in preference 5 per cent. shares, taken in
England. After paying the preference interest, the Go-
vernment shares take 4 per cent., the balance to be
equally divided. Therefore to pay the preference divi-
dend it is only necessary to realise 2i per cent. profit on
the whole capital. It is reported that the line, being
only incompletely opened, already earns 44 per cent.
Profit on the whole capital, showing that the 5 per cent.
is perfectly good, and that something beyond may be
expected. The traffic is even exceeding the original
estimates.—Herapath's Journal.

AN AMERICAN'S OPINION OF CANADA.—The Chicago
Tribune, of the 25th of March last thus writes of
Canada :—During three weeks we spent in Canada, we
did not fail to improve the many opportunities that were
offered us of becoming intimately acquainted with the
condition of the province—her institutions, her wants,
her prospects, and her people. The result has been
that we now entertain, not only a warm affection
for, but a high admiration of, Canada. In the
first place, we admire her people. They are a
race of men who would do honour to any clime,
and whom America might well be proud to rank among
hersons. They are, with but few exceptions, distinguished
for their commanding and noble bearing, their athletic
and healthy forms, their rosy -countenances, and their
warm, hospitable, and generous dispositions. There is
much said of the princely and munificent hospitality of
our Southern States. We have enjoyed it, and
know well how to appreciate it. But we do our
southern brethren no wrong when we say that,
in some respects, .they might take a lesson with
advantage of their cousins of Canada. These men a'..e
also of remarkable information, education, and intrAli-
gence. Converse with them upon any subject of interest
and importance, and they will astonish you by the
vigour of their thoughts, the extent of their knowledge,
and the correctness of their opinions. A more loyal people
can hardly exist; they are enthusiastic in the pudse of
their Queen ; the poorest man among them will throw
up his cap, and stand uncovered in the winter air to
listen to the soul-stirring notes of " God Save the
Queen ;" and will fight at a moment's warning at the
slightest insult offered to the crown. If the men of
Canada thus merit praise and commendation, what
terms of admiration shall we have to use in speaking
of the women. It is not exaggeration to say
that the most beautiful women we have ever
seen are to be found in Canada. We do not
know what dreadful vengeance we may bring upon our
heads by the assertion, but we must say, impelled by a
strict regard for truth, the ladies of our cities must bow
in humble inferiority, in point of personal beauty .and
mental endowments, to their Canadian sisters.",