New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1857-06-19

run fast or Glow g. be pleases. The weight Of the
beat aswinds the suspssniDg ropes, which finally lip
from the holes in the windlass and re main hanging
from the davis. The thimbles Of the Ia shingropes in
the mean time ship rom the prongs and remain hanging
f m the sides OF the boat In thi. operation the force
of man Is made sufficient to control the weight of
boat by means OF the friction puleys above men,
toned the effect OF which Is analogous 20 that OF
turn or two Of rope around post a. exemph6ed
every day on the arrival of steamer when one man
nv this process checks the motion Of boat Of thou-
and tuns. The friction pulley consists of block
with three sheaves placed above the other, their
ceriers in straight line tho sides on the same plane
and their axes parallel The rope is made TO wind it,
wav from the right Of sheave 10 the lef of the
next and once on has the shape of cross section Of
a hollow rail. The nearer the sheaves are 10 eseh
other tie sharper the turnngs Of the rope and the
stronger the resulting friction. Another precaution
which i. IS always pruder take before hand Is that
of fastening NE helm the proper side for turning
the head OF the boat away from the ship. But this
must be done carefully, for if it be turned too much
Oh that side aud the boat lowered OH a steamer at
full speed nishaps nigh. occur This invention has
been thoroughly tried board several vessels of the
English Navy 1t Is found to answer beyond ex-
pectatiop, asd is now adopted by the Admiralty. 1t
i. rapidly making its way board English emi-rant
ships.
CASSoS BALL FOR RTLE-BoRE.-The making of a
practical ball for rifed cannons has been attempted
by MIME and by host of other persons during the
lat twelve years but every attempt has been failure
We believe. however that Mr.. j. VI. Sigoumey, who
hes Just obtained patent has succeeded His ball IS
Lot costly and appears arranged not to nure the
cannon Tie general shape of the new ball is cylin
dro.conic Ike that of the celebrated Mimic rifle ball.
but tie cylinder is smaller than the bore of the
non except at the top and bottom, where two rims
Jeff projecting about quarter of an inch. Between
these rims there are the body of the cylinder three
ribs having the shape Of the grooves in the cannon
inclined at the angle, aud made to project sut-
fcienlly to fill the grooves. After being cast
tie ball is mounted lathe, to which planning tool
is attached, where the two projecting rims are turned
o the exac. diameter of the bore Of the cannon the
three nib, pared 90 to be the exact counterpart of
the grooves. The ball being introduced fits perfectly,
Only is smooth surface being brought into contact with
the cannon.
OPIHALMoscoPF.-This is the comprehensive name
Of an instrument not get generally known even in the
scientific world, by the help of which the interior OF
| the eye may be examined. It's parts are concaye
Mirror with hole in the center, IN which lens is
placed with a second lens, which is separate and nov
able. To use the instrument, a lighted candle Is
placed by the side OF the patient the cOncave mirror
is held in front Of the eye to be examined, while the
movable lens is suspended between the light and the
mirror in such manner as to concentrate the rays of
the first on the second. These rays, after being re-
feced converge ON account of the mirrors eOncayity
toward the retina, and passing through 1t they are
oiyerged and iumine the whole interior of the eye,
10 ,oL
lens placed in the center Of the mirror. This last lens,
and the retina through both of which the observer
has to look form microscope, the multiplying power
of which is 800 This instrument has been the means
Of curing many sufferers, and may be suggestive of
some device for examining other interior parts OF the
body.
SToNE-CUTTISG MACHISE We recently published
| description Of new machine for cutting stone,
| invented by Mr. A. N. George. Since then we have
lad an opportunity of seeing the machine at work. and
were yet more favorably impressed than on our first
visit One Of the results of the togge joint is that for
each turn of the shafts there four strokes of the
chisels thus from FIVE to eight hundred strokes are
the result of practical velocity of from l21 to POO
revolutions of the shafts per minute. The rise Of the
chisel. is quarter of an inch The power applied IS
,tated TO be few horses; but this fact We had no
| means Of verifying. We saw the machine work en-
rranite and cut smooth surface nine inches vile and
three feet loug in minutes. The chses are at
first ground square after they have been used to cut
about fifteen feet long Of granite, they are worn beve
are taken out and turned over, the bevel up; after
cutting fifteen feet more they beveled on the other
side and have again to be turned. All that necessa
~ is to forge them thinner from time to time. The
| stone nav be cut two inches deep For brown-stone
tie feeding has to be four times faster than for granite,
and thestone cut smooth rs require no rubbing
good days work for a stone-cuter is to cut smooth
four ,ouare feet of granite. Calculating from the data
given. the machine would seem capable OF doing the
work Of 900 men. To form practical opinion Of the
| power Of the machine, We mu, consider that the
chsels are placed at distance from each other nearly
eoua to their width this requires going twice over the
stone 10 cut H. Moreover, the cbi.els not being math-
ematjcalIy equal in length, and not wearing equally
third operation is required finishing touch. The
time Of putting up the stone Is also an important Item
Taking all things together, the machine may generally
do a. much as twenty-five men, but never more than
fifty. This is magnificent result, "a in most labor
saving machines the ratio Of their power to hand labor
| il selcom above ten.
| ELECTRO MAGNETIC ENGINE.
| To the Edno, Of The n. y. Tribsns