Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1879-12-10
SCIENTIFIC.

Paris Astronomical NuSeUm.-COnsid-
cradle progress has been made with the
new meuseum now forming at the Paris
Observatory, Among other objects
of historic interest; il will cont ain a
pair of Mercator's globes, dating from
the middle OF the sixteenth century
That figuring the earth is the first on
which meridIans of longitude and par
aliels of latitude were laid down. The
great equat orial lakes of A frica, ii
is reported, are all to be found upon it.
The glass cases contain the first porta-
bic meridian circle constructed on Ad-
miral MoucheZ's plan ;the pendulums of
invaraible dimension employed by the
Captains Fraissinet and Dueperre in
their voyages around the world, for the
determination of the absolute valne of
intensity of the centripetal force and of
gravity at different points of the earth g
surface and the apparatus used by VI.
Cornu, of the Institute, with view TO
determine the velocity of light from OBJ
servations made between the Observa-
tor and the TOwor of Montihery.-
Another glass case, adds the journal deS
De5dtS, contains the standard metre of
the First Republic the toise used l13S
in Peru for measuring a degree at the
equator the toiSe used in Lapland some
short time afterward for measuring the
poplar degree, and the plantinum kilo-
gramme made by the Republican Com
mission of Weights and Measures.
Fresnel's len, the first ever graduated,
is also deposited in the new museum,
and the object glass of tie great astro-
nomer Casssini, which he used in sue
cessiyely determining the existence of
Jupiter's satellites, Saturn's double
ring, the abnormal flatneSs of Jupitor's
poles, and the vast velocity of his rota-
tion, as well as that of Mars. In
another of the cases are to be seen the
dOubly refracting prisms with the help
OF which Arago measured the diameter
of the great planets, Nept Inc excepted.
i Re1r pigment Photographic process,
which is especially adapted TO solar en-
largements, is published by the AssOei-
alton Beige de Photographic, the plan
being TO dissolve wax in benZine,
charge a small quantity of cotton with
the solution, and apply the latter to
light piece OF plate glass. After this,
the plate is provided with a coating of
cOllodion or varnish, and immersed in
water for thirty minutes. 1t is then
taken out and laid fiat on the table.
where ii is coated with a mixture con-
sisting colored pigment, gelaiine and
bichromate of potassium, which, hav-
ing become firm, the plate is allowed to
dry in the dark. Ia addition to this,
pigment paper is taken, ,sensitised in the
usual manner by dipping in a solution
of bichrOmate of potassium, placed
upOn the collOdionIZed surface of The
moistened with water
rubbed down in order 10 obtain per-
feet adhesion, and finally LETT TO dry
The plate is then exposed in the solar
can nera-enlargIng-apparatus-by al
lowing the picture rays TO act, through
the plate, upon the film treated with
bichromate. The exposure is regulated
by the assistance of the photOmeter.-|
The plate is subsequently immersed in
warm water OF thirty degrees, after
which the paper is detached. and the
picture developed in the usual way. Ii
is now fixed, and a peice OF hite gela-
tine is finally affixed 10 the picture by
means oi the roller; and, when this has
become perfectly dry, the picture is
detached.