The midland journal. (Rising Sun, Md.) 1885-1947, 1885-10-09
Scientific.

A perpetually damp copying paper,
always ready for use, is prepared by
dissolving one pound of chloride Of
magnesium in moderate quantity of
warm or cold water, about one pound.
When dissolved, apply this solution
with brush to ordinary copying-paper,
or preferably by means of cloth pads
saturated with the liquid, then place
these pads between any suitable number
of leaves; apply pressure, at first very
moderate, until the absorption by the
paper is complete; then remove the cloth
pads, and apply further pressure; it is
then ready for use. Paper prepared by
this process will remain permanently
moist under ordinary temperature, and
if made dry by any extraordinary neat,
will regain its moisture upon being sub
ject to the common atmosphere. One
advantage of this method is, that the
| sheets of paper viii not adhere to each
other.
A new voltaic battery has been brought
in which peroxide of lead surrounds
the carbon plate as it lies on the bottom
of the cell. The other plate ID also Of
carbon, covered with fragments Of re-
turted carbon platinized The two
plates are placed one above the other,
but separated by 81 sheet of parchment
paper which divides the containing
vessel into to compartments A satur-
common salt, is filed into both CONF.
partments until the upper carbon frag-
ments are partly immersed in 1T. The
electromotive force is 0l6 volt. The
is not in contact with the peroxide of
lead. If other saline solutions such as.
sulphate of ammonia, sulphate OF soda.
Carbohydrate of ammonia, or, even dilute
solution of salt, the electromotive force
does not sensibly vary.
As an example Of the porosityof wood,
an implanted wooden pail showed some
of its slaves saturated and others nearly
dry. Experiments with wool OF the
same character-tf cucumber wood
showed that pieces sawed FROM the same
board differed in their absorptive quail
ties as one end OF the other was set in
water the trials appearing TO suggest
that when the wood was placed in water
rs it grew, butt downward, the water
was absorbed more rapidly than when
the position wa sreyersed. rs Il further
test two pieces wern taken from the same
BOARD, and beth painted on the outside
both faces-but one haG the top end
also painted, and the other the bottom,
or butt end, painted. The one with the
unpainted bait filed and sank, while
the other foated. Perhaps differing
results would have been obtained with
,liffering woods. The fact of position
ffecting saturation seeras to be recog-
lized i'll the frequent custom of revers-
ng fence posts from their natural posi-
ton and in the driving OF piles.
When making diamond turning tools,
is sometimes desirable to- reduce the
| dimensions of hardaAed steel article
that has received lathe finish without
irst drawing the temper, as this necessi-
tutes II rehurdening and retempering.
The usual method OF lathe reducing Of
hardened steel articles by corundum
wheel grinding is necessarily confined
10 straights or tapers, no offsets, eolletss
OF shoulders being amenable to this
style of work. A model maker and
bright mechanic has succeeded in util-
ling the black diamond, or bort, as q
turning tool for hardened steel He
places crystal in the end of piece Of
ircn or brass for fiat turning and one on
the side of the end, or on u corner of the
end, for side or shoulder turning. He
has succeeded in doing some good
+, work with these crude looking tools.
The chips taken from the hardened
steel are literally chips not turnings,
and are very minute. Bat viewed under
the microscope they are seen to be cut
from the hardened steel. and not merely
disengaged crystals. One of the speci-
mems of work with these bort tools is q
we'll finished V-thread, about 80 to the
inch. Two differing crystals of the.