The Princeton union. [volume] (Princeton, Minn.) 1876-1976, 1881-04-28
Curious, Useful, and Scientific.
AN ELECTRIC TIDE.

HcerS OF the British pOStOffice tele-
graph department., has discovered the
existence of the electric telegraph cir
cults. BY long continued and care.
full observations has determined dis
tinct variations of strength in those
earth currents which are invariably
present on all Geographic wires, fol.
lowing the different diurnal positions
of the moon with respect to the earth.
ALARM CLOCK.
In a recent number of Dimgler' s
Polytech1eicees Journal is described
the alarm clock of Herr Pfyffer,
which at the given hour lights a
small lamp. The lamp is above the
clock. Near it is a disk with a
sectional piece cut out and with hori-
zontal axis. This has a spiral spring
and, by means of handle, is turned
round to tense position, in which it
is held by projecting nose and catch.
When the nose is released at the
proper time, the disk springs back and
ignites a match over lamp. The az.
rangement is said to work with great
certainty.
AN INGENIOUS INSTRUMENT.
At the Greenwich Observatory a
very ingenious instrument is in use to
record automatically the duration of
sunshine through the day. It consists
of glass globe hung within a hemi-
pherical cup of slightly greater
diameter, the cup being lined with a
strip Of paper covered with stencil
ink. The globe is entirely exposed
upon the roof, and while the sun is
shining acts as burning glass, and
causes a continuous line to be made
upon the paper. This line will be
broken, however, as often as the suns
light is Obscured by clouds, and thus
a record of the amount of sunshine
for the day will be obtained.
TELE-PHoTOGRAPHY.
Mr.. Shelford Bidwell describes in
nature the result of some experiments
in sending pictures by the telegraph.
This he accomplished by using an APP
paratus resembling Bakewell's we'll
known copying telegraph. In the
transmitter the image was focused
upon a revolving cylinder, to which a
selenium cell is attached. At the
other end of the wire platinum point
passes against the surface of sensitive
paper prepared by passing it through
strong solution of equal parts of ido-
dide of potassium and water. The ar
rangement is such that the selenium
cell on intercepting the current causes
a white spot to appear on the receiver
corresponding in shape and size to the
picture focused on the transmitting
cylinder. The experiments are as yet
crude, but full of promise.
A NOVEL STEAM GENERATOR.
"A Paris firm has lately patented a
peculiar method of generating steam
for a steam engine. At each stroke
Of the piston a certain quantity of
water is projected against two strong
ly heated metal plates. The steam so
produced goes directly to the cylinder,
so that in this arrangement not only
a special generator, but also the valve
system for entering steam, is super.
huous. The mode of action reminds
one of Hooks petroleum motor, or
other engines driven by means of
liquid hydrocarbons. In the example
given in Dinaler's Journal the
vaporiZing surface consists of two
metallic cones, one within the other,
with an interval of about l nm.
between. The hollow space is divided
into chambers, each of which is con-
nected with the side of the cylinder.
The gases play first on the inner sur
face of the double cone, then on the
outer. .-...
STONE COFFINS.
A European firm has been expert
menting with air and water-tight
collins, and has lately overcome some
of the difficulties involved by COM
binatiOn of thin wood and stone COM
position. The composition is formed
of three parts Portland cement and
one part finely washed quartz sand.
For the sake of adhesion the inner
surface of the wooden coffin (which
incases the other) is left rough, as the
wood comes from the saw. The top
OF the stone coffin is arched, in order
to give it greater resistance to outer
pressure, and the wood is shaped to
correspond. The thickness Of the
wood is only 2 to ctm.; that of the
composition IL to LIS ctm. The
weight of such a compound coffin is
not greater than that of the common
oak collins. The closure is perfectly
tight, SO that the bodies of persons
who have died Of infectious diseases
may be safely kept in them in the
house till burial. When the wood has
decayed away in the ground, the stone
coffin remains, uncompressed.
THE FIRST CASTING.
Cast iron was not in commercial use
before the year 100, when Abraham
Darby. an intelligent mechanic, who
had brought some Dutch workmen to
establish a foundry at Bristol, con-
ceived, says Hardware, that iron
might be substituted for brass. This
his workmen did not succeed in effect
ing, being probably too much preju.
diced in favor of the metal with
which they were best acquainted. A
Welsh shepherd boy named John
Thomas had, some little time previ-
GUS to this, been received by Abraham
Darby into his workshop upon recon-
mendation of distant relative.
Whilst looking on during the expert
ment of the Dutch workmen, he said
to Abraham Darby that he thought
he saw where they had missed it. He