New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1875-11-20

cylinder screwed on and containing spring TO press
upward, as fast consumed, a candle placou III J.
IL is closed by 5crew-cap, which forms cohNoh
ent top.
A NEW THEORY OF GALyANIC REsiSTANCE'-hc'
corlng to Herwg. the resistance TO galVanlc cur
rent offered by any metallic conductor is a SuDlec'
that has rs vet been but little understood The phe-
nomena themselves consist principally in the follow
ing: On The nearly uniform rate at which the resist
ance increases with the temperature; ~ metals III a
liquid condition have greater resistance than as
solids at the same temperature; Obi for liquid metals
the resistance increases with the temperature but TO
a much less degree than FOR solids lj the transition
from solid TO fluid. as well as thai from illhd 10
vaporOus condition, Is accompanied with an increase
of resistance; fJl in the ease of saturated metallic
vapoTS diminulion of the resistance Is produceh Dy
elevation of temperature; iOi greater iGsstaiic
Is found at the boundary surface between uuiu ana
solid portions Of the same metal than within the va
porous atmosphere itself.
SPECTRUM APPARATUS OF THE NEW OBSERVATORY
At PoTsDAu.-The maker of the optical apparatus
for the Bothkamp Observatory has lately finished
the spectrum apparatus for the new observatory at
Potsdam, which probably ia the most complete in
strument of its kind. The maker, II. Schroeder.
says of it that the apparatus consists of II single
prsms combined into system according to Ruther-
fnrds method, they being moved automatically and
mathematical accuracy and with the greatest ease
This automatic movement allows of exact differen-
ti1 measurements with hitherto unataned aeon
Tacy and is the first apparatus OF this KIND that mas
been constructed as an exact instrument for ineaSur
ing According to Dr. NOgel, the measurements are
perfectly tUIstN Orhy To the onc-hundIedth part vi
the interval between the dOuble-llne ID OF sodium,
the optical performance Of this spoctrOscope beng
such that the sodium line is separated INTO nine me
lines. Almost all the principal lines OF tne spectrum
ere resolved into groups of lines, while new lines are
seen among those hitherto known.
THE CHANDoR LrGHT.-Ata recent gathering in
Edinburgh, Prof. Archer drew attention 20 a new
invcnnon-tlc Chandor light The apparatus is, in
outward appearance, a small tube three or four
inches long having at one end a revolving button,
which Turns screw, and AT the other a minute an
GUAR point of metal which also reyOlyes, passing
oycra little oriice in the closed head of the tube.
4 continuous tube formed of a delicate strip OF
solidified coodion, with ridge of hardened phos-
phOrus on Of its sides, Is slipped into the tube,
and once in position, can be moved upward by the
screw. BY the same action which presses the upper
end the fuse against eopenngo Of the top the met
al point is turned against the phosphorus. and small
portion of the collodon is thcrcupon igntcd. When
Inc 9Dn1atus i, liked to a gas-burncr, only very
transient flash is needed for the purpose OF ignition
nd not more than a SEVENTEEN part OF the coodiOn
iilse j. consumed in the operation. When however,
he wick of a lamp has 10 be llgnttu by inc otNnc
means a larger proportion of the fuse, the 32d part
in fact Is burned. The apparatus Is either poIta-
ble or adapted to the uses indicated. II a lamp
goes out can be instantly rcghted by turn OF tile
screw instead Of by opening the case, removing the
chimney, and striking luctcr match, thus abort
ing a great advantage III cases where quantities OF
cOEibustible material are lying about
HYDpoGENIZED IRoN.-M. Cailletot, in a paper
presented to the French Academy, contributed the
following interesting points to the literature OF this
somewhat obscure subject. II a solution composed
of "A mixture of the chlorides of iron and ammonium
i, dcconpo-ed with the battery, there viii be found
at the negative pole an accumulation Of metallic
IRON in masses of brilliant luster, great brileness,
and hardness. From this iron after being washed,
either under water or any other liquid, bubbles up
gas which is pure hydrogen. In the air the iron
only loses part Of the hydrogen which it contains.
4 specimen weighing 90 grm., kept for - days In
an open tube. gave when healed Is &C. of Gas, OF
more Than half OF What It contained at the moment
of preparation \ fragment OF the IRON placed uuuer
a test tube filed with water heated 10 90 or 20
C. y causes tumul IuOus disbursement OF gas. One
volume OF iron contains on an average 30 volumes
of gas If piece OF hydTogonzed IRON Is approached
10 burning body, the dl>engaged ~ drogen burns,
and the metal IS surrounded with light lame. liza
piece of this galyauic iron. previously heated, i en-
poycd as the negative pole III a yoltametcr, the
hydrogen of the dccomposcI water escapes IN
abundance from the surface OF the metal, but none
of il appears 10 bc occiuded. Galyauic iron may
readily be powdered but after heating il acquires
certain degree OF ducthty.
ErcmNG PHOTOGRAPHS oN ZiNC, IL RELIEF, FOX
ORDINARY pRISrING.-Zinc plates that may be used
with the ordinary printng-prtss may De prepared
from ordinary Photographic negatives according 10
the following process given by fichtner: 4 way
nish sensitive to light is first made by dissoying
parts of Syrian asphatum in 90 parts of benzoe.
and adding 10 parts OF oil of lavender and then
altering. Much depends on the quality Of the
asphatum, and only such pieces do not melt at
234 and dissolve with difficulty in oil ofturpentne,
should be selected. The benzoe must be entirely
freed by distllation from substances sensitive to
light and must also be entirely free from water. The
oils also must be pure and contain 40 WATER a pure
zinc plate coated with this yarnsh and allowed TO be-
come perfectly dry in dark room on level surface,
is exposed from - to 30 minutes in the sunlight
uuder negative which has been transferred to a
CelaIinc film to prevent inversion of The prints. The
Invisible image tAus formed Is deTeiOpcd b. pouring
upon the plate petroleum, to which j or IL lis
volume of bcnzole has been added, and keeping the
plate in motion and renewing the solvent until the
picture appears in the color OF the YarniSh and the
LIGHTS exhibit the clear metal The plate Is then
washed under stream of watcrtO check the further
action of the solvent aud allowed 10 dry in the light
when the yarnish hardens and acquires the power Of
resisting the acid employed IN etching. The latter
process is conducted usual with dilute nitric acid
until deep enough To allow The OI the plate with
an ordinary prlntng-presS.
NEW PHOTO-IITHOGRAPIIC, OR AUDELTYPE-PRO-
CESS 1t is said that entirely and very supe-
rior process for multiplying impressions from photo
graphic negatives mechanically has been invented
by Aube OF Cologne, and has been named after him,
in order to emphasize It's entire independence of all
previous processes for like purpose If it proves
to be all that is claimed for it, il viii doubtless in
crease the applications of photolithography. The
Use of organic substances, as gelatine and asphal-
tum, is altogether discarded, and no transferring