New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-01-20

the undertaking in the English mines believe that
a force of 90 600 men with the machines can raise
Great Britain's annual product OF l2hJO,VOO TOMS
which requires the labor OF ooOOOo men.
THE MosT TRUSTWORTHY PyRoxETTR-The great
advantages which those enjoy who pursue their
studies in the schools and universities of Germany,
are specially perceived when we examine the theses
of the graduating classes aud of their instructors,
which are frequently published in connection with
annual programmes oflectures. The last programme
of the archaeological school at Chemnitz contains
most exhaustive Investigation, both experimental
and theoretical into the various methods OF mcasr-
ing very high temperatures, executed by froi. "ei
hold with the assistance of DR.. Schneider, who was
a student at the time the observations were made
The methods considered in the course OF this inves-
tigation included the following:
FIRST the expansion of volume; second, the varia-
ton in pressure of inclosed gases the two forms
of the air thermometer; third, the warming OF a
cold mass of any substance by heat, or the caorl-
metric methods fourth the melting of hard bodies
ftth the conduction and radiation OF heat; sum-
the change in the velocity of sound Seren the erect
of heat on optical phenomena; eighth the dissocia-
ton of chemical compounds; ninth the development
OF electricity by the therno-eectrc method; TENN,
the change of the coecien OF electric conductvity
Some of these indeed, needed but few passing
remarks TO dispose of their claims to accuracy vi
them ALL the first method. that OF the air ther-
moInater although most difficult of Application, is
theoretically adapted to give standard results and
the object of the author has been to ascertain
whether some other method cannot be found that In
comparison with this shall be sufficiently accurate
and much more convenient. After detailing the
yarious precautions taken to prepare an air Their
mometer whose results should be of the highest
attainabe reliability, the author explains that the
construction of the apparatus which he employed
was with soma notifications, the same as
that used by Rcgnault, MagHus &c. and con
sists in measuring the pressure OF dell
mite mass of air whose volume Is kept ap.
proxmately constant. The determination OF
the boiling point OF pure zinc at lU5o cehtlgraoe
Tor .S9j Fabrenheit, he considers 10 be the most
accurate that has vet been made and with az per-
feet a standard as this Prof. Wenhold then pro-
cceds to compare the varOUs promoters OF Gaunt-
let's Book aud Oechse. ard shows them TO he quite
untrustwOrthy within the demands 0i modern SCI.
encc even for temperatures of so and less he next
invest the expansion of metals and hard Dodle
as glass porcelain, quartz, &c. and shows that all
these bodies have such irregu ailues IN ther ies
specfc heat of a body at low temperature Is nOt me
same as that at higher temperature: ana the IN
perfection of our knowledge Of the rate at which
specific heat changes, leads WeinhOld, before lnVes
tigatng the value Of the caormctrc promoters To
frs. study the change OF specific heat AT t1lnpera-
lures of 5000, and less for platinum and for ron
The latter proves to he far the better OF the Two
metals for the PURPOSE in view. and the errors of the
result are not too large 10 forbid the use of IRON
i'm the caormetric method. The specific heat OF
platinum varies with curious irregaiarities while
IN that of non IL - apparently very regular. ! ne
very promising me th0d OF LamY, with the dlsSOca-
ton thermometer docs not give satisfactory results
though the author proposes To continue ms re-
searches in tins direction, Finally, Nclnnolu tesls
the SieInenS pyrometcr, whose principle OF
action is the measure of the increase III
the resistance offered by heated wire
10 the passage Of q galvanic current. The instru-
ment employ cd BY him had been constructed for use
in temperatures of less than 800, and for such was
found perfectly Trustworthy. For temperatures M
10 100 IT'S error was small and nearly constant, 50
that this method was decided TO b. the best Of all
that were examined. Wcinhold thus sums NJ his
results which are OF interest to all engaged III these
manufactures requiring the OF high tempera-
lures:
First: OF all the promoters that arc sold ready
for Immediate use, the Siemcns only Is to he recon-
meuded
Second: The calorimetric method used in proper
way, can serve rs pVromcter