Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1875-08-19
MECHANICAL AND SCIENTIFIC.

In stamping sheet zinc in dies much
waste occurs from small differ
ence between the melting point and the
temperature at which sheet zinc should be
stamped to get the best effect To obvi-
ate this waste heat the zinc by dipping in
oil at the proper temperature Scientific
american.
Two specimens of mites have been
found flourishing in the skin of the human
face. One, the Acaropsis Mericourtt, was
discovered in the pimples on the face of a
French officer who had been in Havana,
Cuba A similar species was taken from
the skin of the nose of person in New
Orleans. Mr. Macalister recently exhib-
tied to the Dublin Microscopical Club two
specimens of a species of mite that had
been taken from the face of lady in ia
maica. They We're male and female and
apparently new to science.
Spirit having the specific gravity
90 at sixty degrees Fahrenheit is called
proof spirit; that which is heavier is said
to be under proof, while that which is
lighter is called over proof The origin
of these terms is as follows: Formerly a
very rude mode of ascertaining the
strength of spirits was practiced, called
the proof. The spirit was poured upon
gunpowder in dish and infiamed. If at
| the end of the ombustion the gunpowder
took fire the spirit was said to be above or
| over proof; but if the spirit containe
much water the powder was rendered so
moist that it did not take fire; in this case
the spirit was declared to be below or
under proof.
"A very valuable plastic material has
been introduced in Paris, the constituents
of which are gutta- percha, oxide of zinc,
| amianthus and sulphate of baryta in con-
junction with various colors. The gutla-
! percha is first prepared and bleached by
| being dissolved in rectified naphtha, ben
| zole, or sulphuret of carbon, and when
| the compound does not exhibit sufficient
| elasticity, caoutchouc is added. After the
gutta- percha is prepared and filtration
effected the solution is placed in a still,
| the other ingredients are added, and the
| whole we'll stirred together. Heat is then
| applied until all the volatile oil is driven
| off, when the material is removed to the
| desired molds. 1t is said to be suitable
for quite a variety of nodded works of art
| tissues, or artificial flowers, and when
rolled into sheets forms a substitute for
leather in certain cases
Prof Duncan, one of the ablcst among
European astronomers, has lately declared
that there is strong evidence that the earth
is a solid body now cooling, because the
deeper the pene ration into mines, or of
boring into the earth, the hotter is the
temperature; and if the temperature con-
tinues to increase at depths to which man
cannot reach in the same ratio that it
does at depths to which he can reach, a
temperature Of $3.50 degrees would be
found al a depth of forty-tive miles. AT
this temperature GRANTEES and lavas fuse.
Assuming, then, says Prof. Duncan, the
earth to be a hot body now cooling, as it
cools the rocks must contract--mOreover
those rocks which are rich in silica will
not contract 50 rapidly on cooling as
Others, and consequently herein is a source
Of change in the shape Of the earth. Prof.
Duncan says il is we'll known that surface
changes are going on; that some large
| areas of land are in course of slow rising,
while others are slowly sinking, and that
at one geological period there was a great
| upheaval of the larger portion of the con
tinent of North America He concludes,
therefore, that the globe is cooling I'M
equally; the radiation, too, from some
parts is greater than at others, and in this
! there is consequently further source OF
disturbance.