The Sun.
London, England, 1856-12-22 00:00:00

THE MODE OF "DRIVING ADITS."

At the Government School of Mines an interestieg, lec-
ture on the mode of "driving adits" was rielivere,l by Mr.
Warington Smyth. The lecturer stated that, iu previous
lectures, he had pointed out the method in which lodes
were generally opened ; in tle se ho had told th-ni Low, on
several occasions, the capricious nature of the mineral de-
posits often deceived the miner. In driving a level they
often experienced a great difficulty in keeping to the lode.
The deposits were generally varying in character; some-
times they were rich, and at other periods they became
poor and impoverished ; often, in following the lode
when it took a bend, the miners carried on a level
straight with the anticipation of intersecting it at
some further point. Very often the lode would spl' t
into small branches, and the miners, instead of fol-
lowing the main lode, would prosecute the work-
ing of these small strings until they were entirely exhausted.
In large lodes, where this was generally the case, the miners
often went not through the lode, but by the side of it, and
at different distances drove cross-cuts, in order to obtain
the ore. Several diagrams of lodes under different aspects
were shown. Much depended upon the accuracy of mea-
surement; and in one mine in Wales, where a shaft had
been sunk to make a junction with an edit level, owing to
mistake in the calculation of a few feet the mine was
abandoned. In mountainous countries, and where there
were valleys of great depth, it was always considered
more advantageous to drive levels. In ancient times,
where they had not sufficient machinery, and before
steam power was known, and the amount of time not
of so much consideration as now, edits were more gene-
rally driven than they are at present. The Gwennap
edit, though it is only at a depth of from 30 to 40 fms.,
has been considered of great advantage to that rich dis-
trict, is from 30 to 40 miles in length. In several districts
in the north of England it is considered that greater faci-
lities are given to workings by having alas. At Alston
Moor it is common to look out for a valley contiguous to
the mine, and some edits there are commenced at distances
varying from to 11i miles from the mine. In Derbyshire
companies are especially got up for the purpose of driving
edits, which are there technically called " soughs."
In Derbyshire there is annually about 50,000 tons of lead
raised. The mines there are not so symmetrically or con-
tinuously worked as in our western districts. The miners
there descend and extract the ore at different periods, when
not otherwise engaged. The water that comes from the
surface, so rapidly percolates through the rock, that it is
nearly all dry, and the water runs off through the sough.
The miners there are in general so poor, they have not capi-
tal sufficient to drive a sough for each mine, and comps-
, nies are formed for the purpose of unwatering several, and
these are paid by fixed dues from each. To a certain depth
the layers of limestone in the lead districts of Derbyshire
were free from water, but beyond this the water rises ra-
pidly, and, consequently, it was an imperative necessity
that they should have edits. At one mine, although they
had used hydraulic pumps of from 30 to 40 inch diameter,
they had not been able to fork the mine, so rapidly had the
water risen. In many parts of the world these edits were
very large. In the Hartz Mountains there was one which
was used as a subterranean canal, arid was navigated by
boats. The deep George edit there (so named from one of
our sovereigns) was 13 miles in length. There were several
deep edits at Freiberg, in Saxony, and it was now proposed
to drive one from the Elbe, in the district of Meissen,
famous for its porcelain manufactory, a distance of
20 miles in length, in order to unwator the deep mines
of that district; this would be about 20 miles in length,
and had to be driven nearly the whole distance through
hard gneiss. At Schmenitz, in Hungary, they were now
driving deeper edits under the old ones. In the Alston
Moor district they always endeavoured to choose con-
genial strata for driving, as much time and expense would
be spared by having a favourable rock to go through ; if,
after removing the gravelly detritus, they came to lime-
stone, they were aware how much more costly that would
be than if they went through shale or anything of a similar
nature. In railway tunnels, where time was an important
object, they generally set a pair of men at both ends, and
at distances commenced sinking shafts, in order that they
might work several ends at the seine time; this has like-
wise been done at the deep George shaft.
In the valley of Hodritsch, in the Schmenzitz district,
between the Zipser and Siglisberg shaft, the latter of
which is productive, and the former only used for
ventilation, there is between them a ridge of hills,
about 1,600 fathoms in length. A diagram was shown
of the manner in which this long level is being
driven, as well as the modes, by sinking winees, of taking
off the water and obtaining ventilation. In the Alston
Moor district great attention is paid to where the edit is
to be placed, so as to secure it from floods, or in any way
being inundated. In the mines of the Tyrol, where there is
occasionally danger from avalanches, the miners endeavour
so to place the mouth that it cannot be choked up by the
falling of one of these destructive instruments of Nature.
Boggy or marshy land should be avoided, as it must be
borne in mind that the edit is not only for the purpose of
unwatering the mine, but it is likewise required for ven-
tilation; and, if possible, the mouth should face the pre-
vailing wind of the district, and great care should he taken
to support the edit, so as to protect the men who are at
work. One of the greatest items of expenditure in min-
ing was timber, and a due economy should be used
in the exercise of this. Wood, larger than neces-
sary, should never be employed. The amount of pressure
cannot always be accurately told ; this is different in large
lodes, and where they are in a slanting direction, and here
they require peculiar care in placing them. In purchasing
timber, there are three great questions to be considered—
strength of wood, power of resisting decay, and price; it
should be of such a quality as to resist fracture, pressure
in a vertical direction, or extension. When they had to
deal with large mines, as in the colonies, Wales, and the
coal measures, it was best to employ the timber of the dis-
trict. In Cornwall, which was almost denuded of wood,
the timber used was imported from abroad ; several varie-
ties of fir were used, spruce, as weir as larch, this last being
considered the best. The Scotch fir, pious sylvestris, were
not so much esteemed in Cornwall ; although it Was in
great favour in Ireland, and used there by Cor-
nish-men, who it might be supposed would have
a prejudice against it. Oak was generally con-
sidered the first as regarded strength and durability.
and small poles of it were used for prop wood. Beech and
birch had been made available in mountainous districts,
qut had been found brittle. In some of the southern
countries of Europe, Spanish chesnut was known to answer.
Interesting experiments had beau tried in the French coal
mines, on the respective merits of accacia and the black
and white oak, and the result had been greatly in favour
of the accacia, this having stood for a considerably longer
period than the others.
Mr. WARRINGTON SMYTH alluded to the defective state
of our mining plans in general, and a handsome and well
executed plan of the Schemnitz district was shown, point-
ing out the various lodes accurately and distinctly. A
section of a mine was then exhibited, which, instead of
being in lines, as is generally practised in England, showed
where the lodes had been richer poor, where they were tim-
bered or arched, as well as the strata through which they
had passed. One of the works he could recommend to his
pupils was that of Mr. Sopwith, on isometrical perspective,
this being very useful to the student. The lecturer con-
cluded by pointing out the necessity of working, not only
with regard to the rules that might be defined, but to make
available all the local advantages that presented themselves
in pursuing mining operations.