Amador ledger., 1910-10-07

ducts.
The testing file has been less simple
than one would expect, and machine
testing, substituted few years ago
for hand testing by expert workmen,
has given results far from uniform.
1t has condemned many files known to
be good. At last it was decided to
test the machine itself, and Prof.
w. Ripper, British enigneer, reports
that many experiments have been
made, and that some have given nor
NAL results, while others have shown
extraordinary differences in the cut
ting power Of files appearing to be
exactly alike, and even of the opposite
sides of the same file. The conclusion
has been reached that filing in one
groove seems occasionally to develop
resistant glaze on the work, prevent
ing further cutting, or at least retard-
ing it. 10 remedy this, the machine
has been given an addition causing the
file to change its path from stroke to
stroke, as in hand fling, and the re-
suit is much greater apparent accuracy
in the tests made.
A novel dental surgery has attracted
much attention at the international
Dental Exhibition in London. A pro-
m1nent part of the equipment has been
maple switchboard with aluminium
fittings, the dozen or more switches
controlling the electric current for
such novel appliances as an electrical
mouth lamp, an electric cautery for
cutting away the overgrowth of guns,
an electrical heater for keeping anti
septic solutions at blood temperature,
an electric root drier, an electric hot
air syringe for massaging diseased
gums and at the same time spraying
them with antiseptics. an electric air
compressor, an electric lathe, and so
on.
A new German induction coil sur
passes the famous Spottishwood coil
and gives spark so inches long. 1t
requires a current of 80 amperes at
10 volts. The iron core is 80, inches
long the primary coil consists of 6
layers of copper tape, making alto.
gether 792 turns, and the secondary
coil contains 100 miles of copper wire
about 1-100 of an inch in thickness.
ssMoving x.ray pictures have been
given special attention by j. Carvallo,
of the Marcy Institute in Paris, and he
claims to have overcome the difficult
ties. including that of producing in
Simultaneous impressions on the photo
graphic film. He has successfully
shown the digestive processes of
chickens, mice, frogs and other ami
mails. The food of the ANIMALS was
mixed with basic bismuth nitrate, and
special cinematographic apparatus was
devised for taking and reproducing the
successive views of the stomach and
intestines during digestion. With this
apparatus, exposures of the intermit-
tently moving film can be made at in
tervals varying from the small frac-
tion of second to an hour, the pro-
cess being continued automatically for
periods ranging up to week or more.
The film is made extra sensitive by a
coating of double thickness, and the
pictures are of unusual size-about 2A
inches square. The gray are pro-
duced by self regulating bulb, with
a Carpenter induction coil having IN
interrupter of great rspidity, The
breaks are less than l-100O Of
second, and the currer,t closing IS adj
iustaole bys9iral springs l-l0O Of a
second giving good pictures with a
mo lerate current.
A tubular power boat lately con-
structed is about 80 feet long over all,
but draws only inches of water when
carrying several passengers, and has a
seed of 18 knots an hour. A 6 horse
power petrol engine furnishes motive
power. The two closed cigar shaped
tubes are of galvanized iron, each
foot in diane ter and divided into three
water-tight compartments, and they
are coupled together to support a
rallied platform Ia feet long. The en-
gine is on second platform 319 feet
wide. The rudder is placed between
the tubes at the bow, and thus effects
steering with little loss of speed in
turning.
The cost of plowing by steam, horse
and electricity has been compared in