The workingman's advocate. [volume] (Chicago [Ill.]) 1864-1877, 1870-04-30
SCIENTIFIC AND MECHANICAL


LIGHTNING CoNDUcroRsAIt is well
known that the efficiency of lightning-rods
depends upon the communication Of their
lower ends with water or moist earth. A
German engineer makes the sensible sug-
gestion that to secure this a drive-well be
sunk, down which the lowermost portion of
the rod may be passed to the water be-
meath.
PURIFIoATION OF Water FROM SMoKE
IMPURITIEs.-Several correspondents re-
commend the use Of permanganate Of
potassa for purifying water from the impuri-
ties derived from coal or smoke. Enough
of the salt to give the faintest possible
tinge to the water is recommended to be
added, and as the coloring property Of this
salt is very great, little used in this way
would purify a large quantity Of water.
After standing twenty-four hours the i'm
purities will all be precipitated. and the
sudzing property Of the water is not i'm
paired. Our Western friends who have
been greatly troubled with smokesOiled
water will do well to make a trial of this
simple remedy.
To REMOVE OLD IRON MoLD.-Dr
Thomson recommends that the part stained
should be remoistened with ink, and this
removed by the use Of muriatic acid dill
luted with FIVE or six times its weight Of
water, when it will be found that the old
and new stain will be removed simultane-
ously.
GREAT SUBrERRANEAN WoRK.-The
grandest underground work in the world is.
perhaps, the Ernst August Gallery--one
Of FIVE belonging to a metal mine in Hartz
The mouth Of it is at Gittelda, in Bruins
wick. 1t is 10 feet high, ST feet wide,
and has a fall three-ffths of an inch in a
yard. Like a railway tunnel (but it is
twice the length Of the longsstl, it was BE-
gun simultaneously at various different
points, and finished in thirteen years. The
gallery i 81 miles in direct length but if
its lateral branches are taken into account,
and subterranean gallery navigable for
boats which opens into it, the Ernst Aug
ust Gallery is not less than fifteen miles
long. The survey was 50 skillfully made,
and the plans 80 accurately drawn, that all
the functions of the different sections fitted
accurately into each other; the admirable
precision of the results having been partly
insured By the aid Of magnet weighing 200
lbs, which influenced the compass through
the solid rock IS feet deep, and which vas
kept in one of the working places, while
the compass was held in the other"
FIRING SHOT FROM Rock-CUr MoRTAFs
A recent experiment was tried at Penn
broke Camp, Malta, of firing large stone
shot from q mortar excavated for the pur-
pose in the hard limestone rock. The shot
was 81 inches in diameter, and was elected
a distance of upwards of 400 yards, rising
so high in the air us to look no larger than
a cricket ball. 1t was intended to FIRE of
another shot Of the same description, and a
second mortar had been prepared with an
object but it being cut to near the 6rst
one, the force Of the explosion split the
intervening rock, and prevented any further
OK experiments of the kind that day These
stone mortars remind us Of the gigantic ones
made by the knights of 81. John, and in
tended to throw a shower Of ones or NIT
riale on the heads of an enemy attempting
landing on the coast. Some are still to
be seen in the creeks and bays of the island,
and are well worth passing inspection.
AN IMPROVED BLAST FURNACE.-J.
W. Ormiston, Of Lanark, Scotland, has
invented new method of blast-furnace
construction in which the furnace is
formed with an annular chamber placed
at or near the top Of the barrel Of the
furnace, into which chamber the gases
from the furnace are conducted, upon
which gases a current Of atmospheric
air is directed in any convenient man.
ner, by which means the gases are
capable Of being ignited, and in this
ignited state are passed down a series
Of fues or passages between the inner
and outer Innings of the furnace, where
by the furnace is kept in a very highly
heated state the gases are then car
ried to an snular chamber at the bot
tom of the barrel, from which chamber
they pass to the heaters, and may be
further utilized for any of the heating
purposes connected with the manufac-
ture of iron or other uses.