The Sun.
London, England, 1866-10-25 00:00:00

HAY.

SMITHFIELD.—Meadow hay, £3 lOs to £4 10s; clover,
£4 15s to 15 15s Od ; and straw, £1 15s to £2 4s per load,
Trade dull.

CUMBERLAND.—Meadow hay, £3 lOs to £4 12s 6d; clover,
£4 123 to £5 los ; and straw, £1 los to £2 5s per load.
A moderate demand.

WHITECHAPEL.—Meadow hay, £3los to £4 lOs ; clover,
£4 15s to £5 15s Od ; and straw, £1 15s to £2 4s per load
Trade inactive.

NIGHT SIGNALS.—The difficulty of exchanging
between two ships at sea, or between a ship and the coast,
during the night, has long boon felt by mariners, and
various devices have from time to time been suggested, in
order to fulfil the various conditions of rapidity, distinct-
ness, and simplicity required for the purpose. We now
learn that the French Government has at length adopted
the system invented by Mrs. Martha Coston, of Washing-
ton, a system amply and successfully tested during the late
American war, and now exclusively used by the United
States navy. It was by the aid of these signals the attack
ou Fort Fisher was conducted, and when the first monitor,
the one that fought the Merrimac, was about to sink, it
was by the use of the same signals many of the crew were
saved. A large quantity of Mrs. Coston's night signals are
now being manufactured in the Imperial arsenal of Toulon.
The system is remarkable for its simplicity and handiness.
A box made of tinfoil, and containing a composition
which, when set fire to, will burn with great brilliancy,
displaying two or three different colours in suc-
cession, is fixed on, to a handle held by a sea-
man, the tinfoil melting away as the combustion
proceeds. This is all concerning the mere transmissioa of
the signal; the other and more important part., viz., the
expressing of a given number, is effected as follows :—A
'preparatory box P is first burnt by way of calling attention;
as soon as au answer is returned by means of another sig-
nal A, the real business of telegraphing No. 726, for in-
stance begins. Tho box marked 7is put on .the handle,
and burns away, giving a green light; then comes box
No. 2, which will give first a white and then a green
light ; and when that is:burnt away box No 6 will display
first a red and then a green light. All that remains then
to be done is to look for No. 726 in the code of signals.
The fact of the French Government's adoption of this
system is a sufficient proof of its efficacy.
PHOTOGRAPHIE.— It is a well-known fact that a
photograph taken in the ordinary way is by no means the
exact representation of the person or object, but is, on the
contrary, imperfect in those parts of the image of which
was not, at the time of the sitting, in the exact fociis of
the lens. This is why photographers are so parti-
cular about the sitter's posture, obliging him often to
sit straight and stiff in his chair; to the great detri-
ment of the artistical beauty of the photograph ; be-
cause the greater the distance between the planes in
which two different parts of the body or face are
seen, the more want of proportion will there be in the re-
presentation of those parts. M. Claudet has been lately
endeavouring to grapple with this difficulty in the art of
photography, by starting from the principle that, in order
to obtain a perfect representation of an object, each of its
parts should be successively brought into the focus. If the
image of the nose could bo taken first, and the focus were
then shifted so as to get the eyes in, then again shifted to
get in the ears, and if these three images could afterwards
be made into ono, the portrait would bo perfect. This is
the modus operandi M. Claudet has endeavoured to adopt
by embodying an old invention of his, called the focimeter,
by which the focus may be ascertained that a certain de-
gree of illumination requires. Now if the focussing screen
be made to slide backwards or forwards, till, by the aid of

focimeter, it reaches the exact spot where either the nose,
eye, or ear is in the focus, the different planes of the face
will each have been successively in the focus and out of it
for a certain time, and the portrait will be so much nearer
to perfection. The same result may be obtained in another
way ; instead of sliding the focussing screen backwards
and forwards, the object-glass may be composed of two
lenses, which, by being brought nearer to or removed from
each other, will make the common focus shift its place ac-
cording to the artist's desire. This operation would not in
any case length the sitting, and the interposition of the
common diaphragm would contribute to render the com-
pound images as clear as can be desired.