The daily exchange. [volume] (Baltimore, Md.) 1858-1861, 1858-08-03
TO ARRIVE.
SCIENCE AND ART.

MANUFACTURE OF LEATHER.-The manufacture of
leather has been less advanced by the application of
chemical science than almost any other of the arts
So many physical conditions are involved in the
production of good leather that scientific processes
have been unable to satisfy them all. The hides
are stepped in an eusion of oak bark, absorb tan
min and are converted into leather. Good sole
leather takes about year to tan, and even calf
skins consume month in the operation Chem
lists have indeed proposed substitutes for bark con-
tanning greater amount ftannin; and these-as for
instance terra aponca, Dutch, catechu and dividi-
yi-produce their effects in half the time but the
leather is said not to be so durable
w 18th sumac light skins may be tanned in twenty
four hours, and with the aid of alum even in one
hour; but still the resulting manufactures are not
preferred to the old processes. Atmospheric and
hydrostatic pressure has been used to hasten the
absorption, and heavy rollers have squeezed the So
luton through the pores, but all these methods
have had at bestbut doubtful success. The leath-
er produced by these means is too porous too hard
or too soft, or not sufficiently durable.
IMPROVED PRoDUcTIoN OF BRIcKs-Every inyen-
tlon that reduces the cost of material-that is
makes it cheaper-increases the consumption and
consequently the demand for it. Bricks are every
year used to greater extent for the purposes of
construction in the place of wood, because clay
suitable tor their preparation is found almost every
where, while timber is gradually becoming scarcer
ana dearer. Within a recent period machine has
been introduced which greatly reduces the price of
the article, and at the same time manufactures
The clay used enters the machine dry and bv m cans
of combination of rollers and seves is reduced to
a uniform degree of fineness. The pulverized clay
then passes into the press of the machine, where
there are mouds for bricks into which it falls and
immediately Is subjected to immense pressure;
this pressure gives it the shape and character of
bricks at once, which are delivered from the ma
chine upon little frame with great rapiditv and
are then conveyed to the kiln without the necessity
OF any intermediate process whatever-the moulds
being exactly shaped and made of metal, and the
clay being, by the immense pressure brought to
bear upon it, perfectly fitted to the moulds The
bricks have marbIe-like smoothness of surface
and are very accurately shaped.
THE SPoTs ON THE SUN.-The British Astronomi-
cal Society have presented their medal to NJ Helm
rlch Schwabe, ofDenau, who is stated to have made
daily observations of this phenomenon for period
OF thirty years The alleged result of NJ Schwabe's
Investigations is that of having established with
degree OF probability almost amounting certainty
that the solar spots pass through the phases of
maximum and minimum frequency, and rice rersa,
through period not very different from ten years,
but that during the last three years the results have
shown symptoms of disturbance.
M. Schwabe's merits are in way affected how
ever, though doubt the value of his discovery is
enhanced by this remarkable episode. No longer
is its scope confined to the disclosure of physical
peculiarty in the constitution of the sum- 1t prom
ises to be the means of revealing the prevalence of
principal throughout the solar system coexten-
sive with gravitation, and of establishing another
link in the chain of analoges binding earth with
other worlds, the ultimate effect of which the
future progress of physical research in its most in
teresting departments no one can foresee