The daily union. [volume] (Washington [D.C.]) 1845-1857, 1846-01-26
[ Continued from Gra page, ]

work is proportional 10 the effective pressure OF the
steam and the number Of strokes OF the piston IN a
given Time, or II Is proportional 10 the product Oh
these two variable Quantities.
Now, in the example in question, the pressure Of
the steam (as indicated by the safely.yalye, and
therefore TO be Increased by one aimosphere Is re-
ported to have varied from rs 10 50, or TO have
averaged n . pounds TO the square inch, and the
stream cut of al one-hrd Of The stroke Of the
piston. From these data, the mean pressure in the
cylinder is estimated at 6454, and the effective pres
sure, after deducting for friction according to the
formula of Panbour, at 4l.56.
The number of revolutions Of the engine Tor
double strokes of the piston) Is reported TO have
bee" from So to 81, or to have averaged $50 per
minute.
The effective power Of the engine Tor rather oil
the engines, for there were wo,) was therefore pro-
poronal to SO, S4l .66-or 10 % 80.
STEAMSHIP SPENCER, WITH LorER rRoriLLths
In May, lS45, Loper's proPellers were substi-
tuted in the Spencer for Hunters wheels, (the en-
gines being the same and in the same eondition,)
and experimental uips were made on The Delaware,
and were witnessed by the committee OF the lnsti-
tute. For the required comparison, the trip made on
the 23d Of May, from Newcastle TO the Delaware
breakwater is selected. On this occasion, the
mean velocity obtained was 9.3s miles per hour,
and consequently the labor performed is proper
tonal 10 the cube OF this number, or TO % S. The
average pressure of the steam was 49.09 Tor more
properly by adding the atmospheric pressure 49Os
S<l4 7=63 49, and il was cut of al half stroke.
From these data the mean pressure in the cylinder
is estimated at 5403 and the effective pressure AFTER
dedueung friction at Sass. The mean number OF
revolutions Of the engines was 4++5 per minute.
The effective power Of the engine was, therefore,
proportional 10 4445 ,e32 85-or 10 1860
COMPANION OF THE REsULTs.-From these re-
suits find that the power exertsd by the engines
with Hunters Wheels 10 thai with Loper's pro-
pellers, at 2239 10 l460-or as 10 O652, while the
work done by the wheels was 10 that done by the
propelers at 274.6 to s25 3, or as I To 3O05.
Hence il appears that Lopers propeller does zoos
times more work than Hlnter's wheel, with b52
Of the power, and therefore with the some power
would be zoos 652=4.6, four and sxth-tenths times
more efficient. This 10 very remarkable result,
but il is one which should have been anticipated
from the evident waste Of power insepsrable from
the use Of the Hunter wheels, and u shows that
their further employment ought TO be abandoned.
A change from the Hunter TO the Lopez propeller
was also made in the United States steamship Wa
ter Witch and opportunities Of Witnessing her per-
formances with the latter propeller presented
10 the committee and full notes Of the result have
been preserved. But, unfortunately, although this
report has been long delayed for the purpose, salts
factory information has not yet been procured to
the performances with the submerged wheel, the
essential element of the speed attained being UNI
certain that il cannot be made OF for calculation
Further efforts have been made TO procure the ne
eessary data for just comparison OF the two pro-
pelers in this case and if they shall be successful
1t will be in the power Of the committee 10 make an
important addition TO this report.
VIM. HAMILTON,
..... .... Actuary.