The citizen. (Frederick City, Md.) 1895-1923, 1899-03-31
lNrltten for The Clrizen.l }

Written for the Citizen.
The new current interrupter of
DIR. A. Wehnelt, of Charlotten-
burg, is pointed out by Mr.. a. A.
G. Swinton as much the most not.
able improvement of many years
in connection with the induction
coil, and as likely to find many
important applications in X.ray
work, wireless biography, etc.
Without moving parts, it converts
a continuous current into high
frequency alternating one. The
apparatus is simply a glass vessel
filled with dilute sulphuric acid,
into which dip two electrodes,
one being plate of lead of con
siderable area, and the other a
glass tube containing mercury
and having protruding bit of
platinum wire sealed into its bot
tom. One of the wires from a
source of continuous current dips
into the mercury. The wire of
the tube is immersed consider
ably below the surface and about
half an inch from the lead, and
when the current is turned on, "A
rapidly intermittent are, with a
probable frequency of some hun
dreds per second, seems to pass
between this wire and the dilute
acid. while a torrent of sparks
appears between the terminals of
the secondary of the coil. The
current is passed directly through
the primary of the coil from the
platinum wire and lead plate, no
condenser being used.
An interesting rule for determ-
lining the probability of life is
stated by NJ. Schooling, of Brus-
sells, to have been worked out by
De Moivre, a French mathema.
tician who removed to England
in 1865. 1t is simply necessary
to subtract ones age from So and
to divide the remainder by .. the
result being the number of years
one is likely to live. The chance
of living one year beyond ones
present age is found by NJ. School
ing to be . to at birth, l19 to
at ) years, 512 to l at 10Tears,
347 to at IL years, POI to Fat 20
years, 100 to | at 30 and IS to
at 40 OF 1000 persons of 60
years, 500 will live to 20 years,
120 to 80 and II to 80.
The idea is gaining ground in
France that alcohol from beetroot,
etc, can be made to compete
with petroleum for lighting pur-
poses and that this use of alcohol
would give great encouragement
to French agriculture.
Late repairs on the roOf-beams
of Winchester Cathedral, two
thirds of which were so badly
worm eaten as to require replac-
ing with new oak, have made
conspicuous the work of re-
markable insect. The decay has
been due to the Sirer gigas, some
times known as the horn tailed
saw fly. The fully developed in
sect is somewhat less than two
inches long, resembling large
wasp, and the female is armed
with a long and powerful owl
positor with which it boreS holes
in wood for depoSiting its eggs.
1t is the grubs Matched from
these eggs that honeycomb the
wood, especially fir, creating sad
havoc. The actual b0rer OF the
parent insect, according to Rev.
j. G.. Wood, is marvellous in
strument, being straight, stiff
and as elastic as a Toledo rapier;
and the microscope shows that
its head is provided with long,
sharp teeth, slightly curving in
ward and serving as carpenters
center bit, while the shaft is
armed on each side with sharp
edged ridges acting exactly as
do the sharp ridges of coffee
mill. No more effective nipple
ment could be devised and the
boring tools of modern mechanics
are based on the same principle,
though perhaps less perfect
The principal supply of mica
comes from mines in Bengal.
These, says Mr.. A. Mervin Smith,
have been operated from a very
ancient period, the mica being
sfilI-as for centuries-only taken
out from open cuts in the decom-
posed granite, new places being
sought when the solid rock is
reached. Large fires are built to
aid in the work. The consump.
ton of mica is now increasing,
but seems to have been greater at
an earlier time, as the output OF
these mines was estimated at
about 3, 200 tons in lS49 and only