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A CHAPTER ON SCIENCE AND ART.
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PLATE GLASS.
— At the manufactory of St. Gobain, near Paris, a plate of glass has
been
lately cast, in a single piece, sixteen feet three inches in length,
and
eleven feet six inches in breadth. The ridiculously large mirrors of
which
we Americans are so fond, are all imported, and principally from
England.
The house of Chance and Co. send over a great deal annually, and find
their
account in so doing, notwithstanding the heavy duties exacted from them
by the British government. Messrs. C. and Co. Pay a weekly duty of no
less
than five thousand pounds sterling.
———
RAILWAY GATES.
— We observe that a Mr. T. Lambert, of Stockton upon Tees, England, has
invented an ingenious gate to be employed at the crossings of rail
roads.
This gate turns upon a central support, and is readily managed by one
person.
When open it prevents any one from passing on the road. It is furnished
with an elevated circular signal, containing a lamp, which announces
danger,
at night. Its general effect tends to the protection of life and
property
at crossings, allowing at the same time the greatest possible facility
for passing on the road.
———
THE BOMB
CANNON. — Experiments with Mr. Cochran's bomb
cannon
have lately been made at the Arsenal in Washington, and the efficacy of
the invention satisfactorily tested. The first thirty-two discharges
were
made within four minutes. In another trial seventeen discharges were
made
in two minutes and twenty seconds — in a third, eight were made in a
minute
— in a fourth, three in the third of a minute. This cannon is readily
managed
by six men, while for ordinary guns eleven are required. The charge is
introduced without either swab or ramrod. It can be fired at least
eight times as fast as the common cannon. There is no recoil, and of
course
there is no necessity for breeching, and a hundred shots in quick
succession
do not produce inconvenient heat. These are the main advantages, but
there
are many others which we cannot here specify.
———
VELOCITY OF CANNON
BALLS. — It has been found by recent experiments
that
a thirteen-pounder, with an ordinary charge, impels its ball five
hundred
and six yards in the first second, and that, by increasing the load, it
will send it eight hundred and seventeen yards in the same interval.
———
MEDALS COPIED
BY GALVANISM. — We spoke, in our last
number,
of Professor Jacobi's process for copying medals and engravings by
galvanism.
"The American Repertory of Arts, Sciences and Manufactures" (a very
excellent
periodical, whose publication has been lately commenced, at New York,
by
Professor J. J. Mapes) observes that several scientific gentlemen of
that
city have successfully repeated the experiments of Jacobi. The galvanic
apparatus is very simple, and, by its aid, copper is precipitated from
its solution as a sulphate, in a metallic form, upon the surface to be
copied, making a perfect cast or impression. This discovery is of vast
importance.
———
IMPROVEMENTS IN THE
DAGUERREOTYPE.
— Mr. A. S. Wolcott, of New York, has nearly revolutionized the whole
process
of Daguerre and brought the photogenic art to high perfection. The
inventor,
it is well know, could not succeed in taking likenesses from the life,
and, in fact, but few objects were perfectly represented by him, unless
positively white, and in broad daylight. By means of a concave mirror,
in place of the ordinary lens, Mr. W. has succeeded in taking
miniatures
from the living subject, with absolute exactness, and in a very short
space
of time.
———
TRENCH'S PAPER
MILL. — This is, perhaps, the most astonishing
machine
ever invented. By its means the common rags of the street are
converted,
in one process, and without leaving the mill, into a printed volume,
cut
into sheets and laid ready for the binder. Dr. Quin, in a late lecture
upon the Mechanic Arts, at the New York Mechanics' Institute, remarked
very truly concerning Mr. Trench's invention, that a person might
"throw
in his shirt at one end and see it come out Robinson Crusoe at the
other."
Mr. T. has deposited in the rooms of the Mechanics' Institute a single
sheet of paper containing six copies of Town's Spelling Book. He says
that
he can manufacture, if necessary, a single sheet one mile in length.
———
THUNDER. — It
is the opinion
of M. Arago that thunder is never heard in the open sea, or in islands
beyond seventy-five degrees of north latitude; and he thinks the same
remark
is applicable to continents. No reason is yet assigned. The opinion
itself
is based upon a variety of interesting researches.
———
THE COMPRESSED
AIR ENGINE. — We mention
in our
last a suppositious invention of a Mr. Bissell, of N. J., which
professed
to make use of condensed air as a motive power, and spoke incredulously
of the attempt. It appeared obvious that no greater power could be
obtained
from compressed [page 247:] air than was employed
in
its compression, minus the friction of the compressing machine. However
Mr. Bissell may think of getting over this radical difficulty, (one
involving
a leading principle of physics) still he can have no claim to be
considered
an inventor; for we find that the very same thing has been attempted,
some
time ago, by M. Houdin, and a patent of importation granted for it in
Belgium.
———
ANNUALS. — In
the "Art Union,
of Journal of Fine Arts," it is stated that during the seventeen years
in which annuals have been published in England, seven millions of
dollars
have been expended upon them. A table is given which shows that the
engravers
come in for the largest share of the spoil. The sums paid them
precisely
double those paid the poor authors. The binders come next after the
authors.
———
ÆROSTATION.
— It is announced
in the Parisian papers that M. Garnerin is fitting up a balloon at the Ecole
Militaire which will accomplish the
desideratum of navigating
the air in any direction at the will of the æronaut. On each side
of a boat (which serves for car) are placed four boards something like
the sails of a windwill [[windmill]], which Mr. G. moves by the
assistance
of a machine in the interior, "the secret of which is known only to
himself."
The resistance made by the air when struck by one of the boards "acts
upon
the balloon and carries it forward like a bird flying. Mr. Garnerin has
already made several essays, which have been completely successful."
This statement is nothing better than
downright nonsense.
It has been more than once demonstrated, a priori, that the
control
of a balloon in the manner here described is impossible. Among
scientific
men the idea ranks only with such projects as the quadrature of the
circle,
or the doctrine of perpetual motion. It is more than possible that the
machinery here spoken of is the same as that of Mr. Green, the London
æronaut,
by means of which that ingenious gentleman proposes, not to direct the
horizontal course of his balloon, but merely to regulate its elevation.
It is composed o two fans, or blades of wood, attached to a spindle
which
passes through the bottom of the car. The fans are of one longitudinal
piece, to the centre of which the spindle is fixed, in the fashion of a
windmill, with but two winds or arms, their blades presenting a given
angle
horizontally, in which direction they move. A London paper describes
the
effect as follows.
"A miniature balloon of about three
feet diameter,
was filled with common coal gas; to this were attached the hoop,
netting
and car, and in the car a small piece of spring mechanism was placed,
to
give motion to the fans. The balloon was then balanced; that is, a
sufficient
weight was placed in the car to keep it suspended in the air, without
the
capacity to rise or inclination to sink. Mr. Green then touched a stop
in the mechanism, which immediately communicated a rapid rotary motion
to the fans, whereupon the machine rose steadily to the ceiling, form
which
it continued to rebound until the clock-work had run out. Deprived of
this
assistance, it immediately fell. The reverse of this experiment was
then
performed. The balloon was first raised into the air and then balanced.
A similar motion was imparted to the fans, the action of which in this
case was, however, reversed, and the balloon was immediately pulled
down
to the ground by their forces.
A more interesting effect still was
then exhibited.
The balloon, with the guide-rope attached to it, was balanced as
before,
the guide-rope having a small brass weight fixed to the end of it. The
fans were then removed from under the car and placed sideways upon it,
by which their action became vertical. Upon motion being communicated,
the balloon floated in a horizontal line, dragging the guide-rope after
it, with the weight trailing along the floor, and continued to do so
until
the mechanism ceased, when it immediately became stationary again.
These
experiments were frequently repeated with complete success."
The guide-rope here mentioned is an
invention very
fully described, by Mr. Green himself, in the March number of the
"Polytechnic
Magazine." It is another aid in the attempt at regulating elevation — a
very material point. There are many causes continually in operation to
exhaust the gas in an ascension — but none is more potent than the
variation
of distance from the earth. When the balloon gets up very high, into a
rare stratum of atmosphere, the gas is excessively expanded and must be
let off to prevent explosion. Meeting then with a cloud, the silk and
cordage
become saturated with moisture, and the whole machine falls with
rapidity.
Ballast must be thrown over — and to remedy this evil, is a very long
cord,
wound upon a windlass, and with several small buckets at its lower
extremity,
so contrived as to act either as floats, relieving the balloon of their
weight by resting upon the sea, or as additional ballast by catching
and
retaining water. Mr. G. also gives an account of a drag by which his
progress
may be retarded while in the air. He speaks with entire confidence of
the
feasibility of crossing the Atlantic from America to Europe, and we
have
no doubt that he will shortly accomplish his design. He asserts that a
current of air sets invariably from the north of west, at an elevation
exceeding ten thousand feet — that in several hundred experiments he
has
never once found the case otherwise. |
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