New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1851-02-04


by chance it may not have been already perceived
or suggested by others.
First of all, it will be to the purpose to compare
the dimensions of the Baltic and Of one OF the Gu
nard steamers the Asia as they are laid down in
the draughts published by Currier, 30 Nassau St
Length deck ................ 2s23 feet 2SO feet
Breadth OF beam ............,..... - " 80
Depih Of hold ............. SIT q
Diameter OF wheels .............. So - SO -
Horse power-twO engnes.......llo0 each. 400 each.
Every one will be struck by the fact, that, there
being, between the two rival steamers so mode
rate difference in dimensions, there should be
SO great a difference in the horse Power-not less
than 1900 to $780, This circumstance would have
led many to anticipate that the Baltic would not
fail to beat the Asia by many days in crossing
the ocean. If a mathematician had dared to fore
tell, that, on the contrary, the attic would scarce
" equal the Asia in velocity, both he and his theo
ny would have been laughed at. Generally how
ever, Experience herself takes care to revenge
the honor Of her learned daughter and guide, The
DRY and such has been the case on this occasion.
Let us seek for the reasons.
We must first bring to our recollection that,
other things being equal, the quantity OF power
necessary to obtain given velocity in fluid is
proportional not simply to the velocity Itself but to
It's cube A double velocity requires an eight
times greater power; a treble velocity, power
twenty seven times greater. Were the immersed
midshp. sections of the Baltic and Asia equal and
their machinery equa ally perfect the former would
yet have create speed than 10 miles per hour
when the Asia would have IL. But as both are
nearly OF the same length, the Baltic whose bur
den is greater must have breadth and depth of
immersion absolutely and relatively greater than
the other bat the depth which would slngly
answer to the weight OF the hull and OF the useful
burden is very much increased by the weight OF
the engines and coal. AS steam engine cannot
consume less than five pounds of coal per horse
an hour the Baltic must consume In aslnge hour
not less than l 900 pounds OF coal and whereas
the rules of the most ordinary prudence must re-
quire her always to take In store OF iuel Tor nj
teen days at least 1t makes the vast load OIL 5OO
tuns of coal. How much is the weight OF the en-
gines | do not know but 1t is certainly enormous;
from indications privately obtained should Judge
it is not inferior to the whole weight OF the coal
Consequently a very considerable part, perhaps,
more than half OF the whole power OF the en-
gines is emp oy ed in nothing else bat IN carrying
themselves and their supply OF fuel
Be it as it may, the breadth Of the two steam.
ers we are conn pairing, being respectively 40 and
So and the depths Of hold 324 snd ~ II we SUB
tract about 10 feet as an allowance for the neces,
saly elevation of the upper deck above the water
and add something to the depth of tue attic tor
the necessarily greater thickness OF the bottom,
we may well suppose that the hight and width OF
the immersed midship sections OF both steamers
are respectively As by "a, and 80 by II, therefore
the resistance Of the sea to the steamers pro-
gress, the veocities being equal, would be nearly
ia the ratio of $50 646 Consequently to OBJ
tain the same speed, the force of the Asia being
500 horses that of the b attic should be, proper
tionally TO the sections, 1887 bat 1t Is 2,2OOi
then, were steam applied TO equal advantage In
both ships their respective velocity would be IN
the ratio OF the cubic roots OF l,33l and 2,2Oo,
which are nearly 5. ll3 and 037. That is tOsay,
if the average passage Of the Asia be reckoned at
twelve DAYS that OF the attic should be only ten.
Now this is not the case. In good weather. oil
course, she will have shorter average passages
than the two last but the Asia also will then
make shorter voyages. There must be- there
fore. a reason why the Baltic, and her fellow
steamers of the American line, cannot have that
full advantage of nearly two days, which belongs
to the proportion OF their steam power to their re-
sistant transverse sections
The main re ason lies in the comparative small
ness of the paddle-wheels. To prove this am
obliged TO demonstrate general theOrem, name.
lv. that the larger the working surface OF the pad
dies the greater the vessels velocity must be- the
quantity Of steam employed being the same Let
A be the reduced surface Of the paddles, by which
mean the hypothetlc surface OF single paddle
which beating perpendcularly the water with the
velocity proper to the actual inferior paddle, would
give an effect equivalent 10 the joint effect of the
several paddles partially or totally Immersed with
different inclinations. The pressure which this
redpced surface exercises backward against the
water by its revolution, is IN the compound ratio
of itself and Of the square Of its absolute neg
alive or backward velocity, velocity Which we
shall call z, as we call ? the steamers velocity
Letb.c d, E. etc. be constant coetfcients. The
resistance OF the sea TO the advance OF the steam
is proportional 70 the square q. OF her velocity
By the fundamental principles OF Dynamics "hen
is uniform, this resistance must be equal 70 the
pressure exercised by water in the contrary dl
rection against the paddles by virtue OF their
bsckW ard motion; we shall have therefore
u ID u
Here II appears that we may augment the
ships velocity Z either by increasing or u we
could DO both were the power Of the engines IN
definite such not being the case. We cannot aug
ment either Of the quantities, A, u, without d.
uinishing the other. Now by augmenting we
have an advantage much superior to the disad-
vantage arising from the obliged diminutlon oil u.
Let as call T. the quantity OF steam constantly
expended by the engines IN an unit Of time
this quantity is IN the composed ratio OF
the density OF steam IN the cylinders, and
of the number Of strokes in the unit OF time.
But the density OF the steam is proportional
10 the pressure upon the surface OF the pistons,
and this pressure must be in a constant ra'
rio with the pressure A ~ OF the paddles
moved by the pi1tons and the number of strokes
OF the latter in the unit Of time, being equal 20
twice the number Of revolutions Of the paddles
must also be proportional TO the velocity OF reVo-
lutions Of the paddles, which IS n--p. IhereiOf0
Cd Il VI (U7rvI.
IL heyalor of 4, taken from this equation Dc
substituted in the former, we shall have
V=g+T
Here IL il visible that 70 and & being constant