New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-09-05
APPLIED SCIENCE.

and hind wheels are OF Inc same size, ana WHICH
pole lies lower than the axle.
MIXTURE OF PLASTER OF PARIS WITH MARSH
MAILow RooT.-Addition of two to four per cent OF
powdered marsh-mallow root to plaster OF paris al
fords that sets in about an hour and becomes
30 hard when dry that it may be sawed ana turned
and which is used for the manufacture OF dothoG
dice, &c. With eight per cent OF the TOO. thi
harder mass is obtained 1t may be rolled l5to 'nin
leaves, and be painted, varnisned OF ponsneu'
PREPARATION OF CoRALItNE. From recent
study of coralline, Commae concludes: l. thattis
obtained at temperatures from 1892 to BOZ, the pro-
duct being larger and the process more rapid at the
lower temperature. 2. the quantity OF oxalic acid
required is not as large generally stated Cor
alline forms no definite salts but only lakes A. 1ei-
low coralline is no acid and rosoc acid is conse-
ouently a misnomer. 8. Red coralline is no amid
of the yellow since 1t contains no nitrogen
DESTRUCTION OF NIaHT-FLYING INsEcTs.-Mil-
lions of insects injurious to trees may be destroyed
by keeping up numbers Of small fires from twilight
to midnight and surrounding them with circles of 20
TO 80 tarred stakes, not more than SIX inches apart
Although few insects will be found burned to death,
since they soon to acquire dread of the fire,
many will be caught in the tar while moving about
in the warmed stratum of air or to and from the
fire.
CLEANING GuT ARTICLEs.-Gilt metallic articles
may be cleaned by rubbing them very gently with
soft sponge brush dipped in a solution of one
half an ounce Of potash, or one ounce of soda, or
still better of one-half an ounce of borax in pound
OF water then rinsing them in pure water and dry
ing with soft linen rag. Their luster may be I'M
proved IN special cases by warming them snghtly
and then rubbing them very gently. Gilt frames.
DC. should only be washed with pure water, RUBBING
very gently with soft sponge or brush.
wEArHER-PRooF COATING FOR ZrSc.-According
TO Puscher the addition of sesquioxde of iron to So
iii
red permanent coating for zinc; and by the substi-
tuition of other pigments lighter or darker coatngs,
of any desired shade may be impaired to architec-
tural zinc castings. Deep black, permanent char
acters may be formed on clean sheet zinc by writing
upon it with a steel pen with a solution OF equal
parts of chlOrate of potash ard sulphate OF copper
in thirty-siX times the quantity OF hot water and
washing and drying the zinc after few minutes
This fact may be especially useful to gardeners.
THE EFFECT OF GALvANIC CURRENT ON ELIAS
ITCHY AND LENGTH OF THE CONDUCTING WIRE
As the result of a very complete investigation by
Streintz into the effect of galvanc current on the
elasticity and length of the wire through which it is
passing the author gives the following conclusions:
/. The current does effect change in the elasticity
of its conducting wire, but only by virtue of the
heat that is thereby developed.
2. The current extends the conducting wire more
than it would be extended by simply warming up
TO the same temperature. Such excess of extension
is inappTeciable only in the case of hard steel.
8. The galyanc extension is effected not suddenly
in consequence of the completion of the current but
gradually, in manner similar to the effect produced
by heat.
of an eleetTo-dynamic Tepulson but probably con-
sists Of polarization of the heat vibrations.
THE CoNDUCrvITY OF METALLIC VAPoRs FOR
ELECTMCITY.-TheeO nductivity of flame for galvanic
currents is known to be greatly exalted by the
presence Of metallic vapors, and Herwig has been
led to inquire whether gaseous layer entirely
formed of such vapors would not show good con-
ductvIty even at low temperatures He expert
mented with mercury, dense vapors of which can
be used several hundred degrees under white heat.
He finds the vapor conductor to resemble that of
the vOltaic rather than that of a simple metallic
conductor There is peculiar transition resistance
which is great in comparison with the hindTaDces
which the current finds within the vapor layer
itself that the total resistance is in great meas
nre independent of the extent OF the vapOr layer.
The transition resistance is less with increased cleo
tromotve force of battery strength of current. |
The vaporizaOn in the positive mercury surface is
increased by the current, an effect similar to that
noticed in the Voltaic arc in which, if the electrodes
be mercury and platinum, the mercury is vaporzed |
only when it forms the positive pole. Using pla-
tinum point and mercury surface Herwlg finds |
the resistance of the vapor greater when the mer
curry surface is positive.
MELTING AN EXTRAORDINARY Mass OF PA |
TNUM-The largest mass of the alloy of platinum |
and Iridium that has ever been melted at opera
ton recently fused at Paris in the presence of
the Executive Committee of the National Metric |
Commission This mass of the alloy in question was
intended to be run into mold of such shape as to !
afford eventually number of new line standard /
meters which will all be cut from this single ngot,
and il is expected that the surplus metal will even
then be sufficient to make all the required new
standard weights OF Kilograms and a number of end |
standard meters. The weight of the great ingot in
question was $50 pounds avoirdupois; its length |
about IS inches; its breadth inches; depth
2. inches The process of melting was facili
tated by first dividing the material into small pieces
a small quantity was then melted, and to it were
gradually added the remaining portions in the form
OF long thin bars. The heat required was obtained
by means of an OXyhydrOgen furnace fed by six gas
tubes each about one inch in diameter and supply
ing the ordinary Illuminating gas, aud another set
of tubes which furnished the requisite proportion of
oxygen. The latter gas was made on the premises |
and stored in large gasometer: For obtaining |
sufficient blast, the power OF hfteen-horse steam
in melting the entire mass of $50 pounds was one |
hour and three minutes, of which the first forty |
minutes were occupied in melting the first half of
the material.
LIPPMANNs SMALL ELECTRO-C APLLARY MoToR.-
The following fact has been applied by Lippmann in
the construction of very novel, small motor, pro-
aucing 100 revolutions per minute and which is so
exceedingly sensitive to the slightest electrical
rent that its use for eecrometrca purposes is sug
gested as we'll as its possible adaptation to the
peption of messages by cables If globule of
mercury, several millmeters in diameter, covered
with water calculated with sulphuric acid and but
slightly colored with bchromate of potash, in a
glass OF porcelain vessel is touched the side with
an iron point il at once contracts thus altering its
shape again expands until it touches the needle |
point. then again contracts aud giving rise to