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Page 9
2. A 2 in. hole drilled 4 ft. 6 in. into the side of the coal about 10
in. from the top, fast ends not holed under, width of space 10 ft.
This was purposely a "blowout" shot. The result was again most
satisfactory, the charge exploding in perfect darkness.
3. A "breaking up" shot placed in the stone roof for "ripping," the
hole being drilled at an angle of 35 deg. or 40 deg. This is intended
to open a cavity in the perfectly smooth roof, the ripping being
continued by means of the "lip" thus formed. The charge was 105
grammes (nearly 4 oz), and it brought down large quantities of stone.
4. A "ripping" shot in the stone roof, hole 4 ft. 6 in. deep, width of
place 15 ft. with a "lip" of 2 ft. 6 in. This is a strong stone
"bind," and very difficult to get down. The trial was most successful,
a large heap of stone being brought down and more loosened.
5. A second "blowout" shot, under the conditions most likely to
produce an accident in a fiery mine. A 2 in. hole, 4 ft. 6 in. deep,
was drilled in the face of the coal near the roof, and charged with
105 grammes of roburite. A space of 6 in. or 8 in. was purposely left
between the charge and the tamping. The hole was then strongly tamped
for a distance of nearly 2 ft. The report was very loud, and a
trumpet-shaped orifice was formed at the mouth of the hole, but no
flame or spark could be perceived, nor was any inconvenience caused by
the fumes, even the instant after the explosion.
_Further Experiments at Wharncliffe Colliery._--On Tuesday, October
25, some very interesting surface trials were arranged with great care
by Mr. Walker. An old boiler flue was placed vertically, and closed at
top by means of a removable wooden cover, the interior space being
about 72 cubic feet. A temporary gasometer had been arranged at a
suitable distance by means of a paraffin cask having a capacity of 6
cubic feet suspended inside a larger cask, and by this means the
boiler was charged with a highly explosive mixture of gas and air in
the proportion of 1 to 12.
1. A charge of gunpowder was placed in the closed end of a piece of
gas pipe, and strongly tamped, so as to give the conditions most
unfavorable to the ignition of the firedamp. It was, however, ignited,
and a loud explosion produced, which blew off the wooden cover and
filled the boiler tube with flame.
2. Under the same conditions as to firedamp, a charge of roburite was
placed on a block of wood inside the boiler, totally unconfined except
by a thin covering of coal dust. When exploded by electricity, as in
the previous case, no flame was produced, nor was the firedamp
ignited.
3. The preceding experiment was repeated with the same results.
4. A charge of blasting gelatine, inserted in one of Settle's water
cartridges, was suspended in the boiler tube and fired with a
fulminate of mercury detonator in the usual manner. The gelatine did
not, however, explode, the only report being that of the detonator.
After a safe interval the unexploded cartridge was recovered, or so
much of it as had not been scattered by the detonator, and the
gelatine was found to be frozen. This fact was also evident from an
inspection of other gelatine dynamite cartridges which had been stored
in the same magazine during the night. This result, although not that
intended, was most instructive as regards the danger of using
explosives which are liable to freeze at such a moderate temperature,
and the thawing of which is undoubtedly attended with great risk
unless most carefully performed. Also, the small pieces of the
gelatine or dynamite, when scattered by the explosion of the
detonator, might cause serious accident if trodden upon.--_Engineering._
* * * * *
THE MECHANICAL REELING OF SILK.
When automatic machinery for thread spinning was invented, English
intelligence and enterprise were quick to utilize and develop it, and
thus gained that supremacy in textile manufacture which has remained
up to the present time, and which will doubtless long continue. The
making of the primary thread is the foundation of all textile
processes, and it is on the possibility of doing this by automatic
machinery that England's great textile industries depend. The use of
highly developed machinery for spinning cotton, wool, and flax has
grown to be so much a part of our conception of modern life, as
contrasted with the times of our grandfathers, as often to lead to the
feeling that a complete and universal change has occurred in all the
textile industries. This is, however, not the case. There is one great
textile industry--one of the most staple and valuable--still in the
primitive condition of former times, and employing processes and
apparatus essentially the same as those known and employed before such
development had taken place. We mean the art of silk reeling. The
improvements made in the production of threads of all other materials
have only been applied to silk in the minor processes for utilizing
waste; but the whole silk trade and manufacture of the world has, up
to this time, been dependent for its raw silk threads upon apparatus
which, mechanically speaking, is nearly or quite as primitive as the
ancient spinning wheels. Thousands of operatives are constantly
employed in forming up these threads by hand, adding filament by
filament to the thread as required, while watching the unwinding from
the cocoon of many miles of filament in order to produce a single
pound of the raw silk thread, making up the thread unaided by any
mechanical device beyond a simple reel on which the thread is wound as
finished, and a basin of heated water in which the cocoons are placed.
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