May, 1881.
THE WEST SHORE.
TBE MAGNETIC NEEDLE, AND MINING
FLANS.
Recent event in onnneotinn with mining
operation! thow most forcibly tht great import
ance of having the working plans of mine al
moat mathematically oorrect, yet we have had
plain proofi that many, oouiidured in every
way moat reliable, hare just been the reverie.
Many of the mining iiirveyi now In uie, aayi
the London Mining Journal, oaonot be relied on
within five or ten yardi at a distance from the
haft, and the protraoting of one line from the
preceding onee, and to on in succession, perpsto
tea every error, and it a system of "judging,"
aa it ie termed, that should not be adopted by
the mining engineer. In many instances the
taking o( the magnetic variatione have been en
tirely disregarded, and thia hat led to many
error appearing on plane, In taking the
meridian there was a great deal of dilfeionoe in
the observation taken on one day and that ob
served on another. To some extent, no doubt,
the atmosphere affected the needle, fur oxygen
being a oomponent part of it was a sultitanoe
that attracted the needle, and it ws also
probable that the heat of the sun also affected
it. The diHerooo in the weather and the
seasons of the year, it may be token, bad a
tendency to a variation of the needle from the
true meridian. To dvtermiue the deviition of
the plane of the meridian, or of the due north,
it was usual for the direction of the pole star to
be taken while the lint star in the tail of the
constellation of the Great Bear was passiug pre
cisely underneath the polar star, The true pule
was a point in the line joining the two star
a little removed from the pole star, just opposite
to the next star whioh is visible to the uaked
eve. It hea been aaid that greater accuracy has
been obtained by taking what is termed the
"solar meridian, but how this oin be done doe
not appear to be known to many of our miniug
maneitera. One gentleman haa iuformod Us
that he ha taken it frequently by a transit In
strument! all that waa required beiug to find
the proper time the sun- was passing the me
ridian of a oertain place, anil then tiling, on
torn important station on the eurface,make the
observation at the prober time. The ordnance
maps were generally tolerably correct, and
they were used to find the longitude of the
nlana wanted or required. Aa to taking the
time, which, of course, waa required to be most
exact, it was done by ascertaining tne lrcn
wioh time at pleo and then onrrecting it by
means of calculation, to as to obtain the mean
time at Greenwich.
Aa to. old mining plans, at a rale, it it no
doubt oorrcot to eey that if they were now
broouht into use. to have the workings oorreotly
carried on tush oonld not be done without going
and compering thorn or getting the true me
ridian again. But it baa been stated by one of
nor minina enaineera who ha paid a great deal
of attention to the subject, that by adopting
the eolar meridian there would be a universal
similarity in ail plana, at every plan would be
drawn on it proper meridian. Every plan
throughout the country would be as parallel aa
possible, and by that meant lhay would be able
to aomnare them at 000. However, the tak-
ms al aha solar meridian aa yet has not been
adopted by many ef our mining engineers, who
consider it of mora importance to know the
variation of the compel from a oertain line.
Htiil U baa tta advocate, whose number will in
ail nrobabilitT increeea, for it baa tU ettieo-
tiooe, e Dentally among the young member of
the proleesioe.
Doe of the simpler methods by which the me.
ridiaa eaa bo approximately determined ia by
drawing a thin rod vertteally oe a drawing
board or onus level anrfaoe, the ebsdow cast by
the rod being measured a abort lime before mid
day, and the vicinity marked. Through the
pout with the rod as a center the are of a eirole
u atraoa. wheel the) txtreauty of the ahadow
again toaohea the art) after midday, the point
when it leeches is marked, and midway be
tween the extremities of the two shadow! may
be found the point, which ia in the same me
ridian a the rod itself. It ia, however, most
desirable for fntnre re'erenee to mark by stronj
stakes a several chain distano on either side
of tne shaft the meridianal line whioh baa been
taken as base for the survey. In the survey
ing of boundary lines on the surface. Or of the
mainwavs in the skeleton ot the survey under
ground, the oompasa should be entirely dis
carded. Where very great oar haa not been
taken it may be aaid the net of the magnetic
needle underground, where tht greatest aocuraoy
to neoeasary, ha led to many error whicn
have led to litigation and loss of time by driv
inn in the wrona direction, purveying, how
ever, can be done without a needle, especially
where there 11 only one shall, and thtaoan De
Heated by two thin oopper wires carrying
heavy weighta at the bottom immersed lu
huoketa of water to diminish the osoillalinn, a
deal straight edge being hied so aa almost to
touoh each wire at right angle to in lines lie-
ween tbem. Tbtextromoa ol lit or ten suc
cessive oscillations should be marked with a
pencil on each straight edge, and the meau taken
with a pair of 00m passes, and the wires Hied to
such mean points. .Standing liehind the wires
the surveyor should next tend a oandle along
the headiug aa far aa it oould be teen, and Hied
in aline with the wire, and thia operation
should be repeated In (lie opposite direction,
Dtaoinu a oandle against one of the wlrea. and to
oheck the whole it should be teen whether the
three caudlea are exactly in line. The lattir,
being the batia of the whole underground survey,
should be permanently marked by a few pegs
driven into the roof with nails in them, or by
some other marks. On the aurfao permanent
pegs should be placed at some chains distauoe on
eaoh side of the shaft in a line with the wires.
llv thia maana there i obtained a line on the
lurfaoa exactly oorrrsoudiug with the base line
of the nperationt underground.
This system haa bten found to be a really
good one after the most sever teat that it was
possible to have, not only in ordinary mining
but in tunnelling aa wen. surveys inr uie pup
pose of ascertaining the exteut aud direction ol
underground workinve should be to trustworthy
and accurate aa to suable the surveyor to show
from this man or ulan the very point on the
surface below which the mineral haa been taken
awav. and to what extent the tubterrauean ex
oarationa have extended. This, under ordinary
oiroumstauoce be oan do by taking the borison-
tal dimensions of the eurlaoe area Iront which the
mineral baa been excavated beneath. Another
means treuuentlv need in surveying waa by
having three atone in line, and testing tht
oompasa frequently, when a correct eurvs;
oould be ensured bv a competent surveyor, am
thia oould be done in thin teams ot niinsral
where the theodolite could be brought Into use.
The magnetio needle, however, waa a rather fa
vorite mode ol surveying, bin in oonneotioa
with It) but it waa affeotod by magnetic atone
and Ironstone, Mill, in making survey of
minee there oan tie no uuostlon as to the Import
ance of the taking aoourate not of the mag
netio variations, so as to ensure the aocuraoy ol
mining plana, and these have at many places
been entirely iunored. and with serious eonse-
nuenoee to the owner of mine. In 00 case
..... , , t 1 1
we arc told 01 two oeua oi ouai wniuu were
worked simultaneous' aooofding to the plana,
and th result waa that there was a difference
of aeveral chains, which greatly astonished the
enmneer. Duly reoeutly, V, to an action
tried in one of tlie Superior Court, heavy dam.
under th notice of mine manager and mining
engineer, on whom to muon reaponaiuiuty
rest lor the aalety ot mote employed uoaer
them, e well ee fnr th eeetirity of the premwrly
plaoed in their keeping,
ages were awarded vo a mine-owner im st
end setUi.i minerals by Uie party who bad
tttnaluivniul hia huuiidarv. owinii to the Ineoua
iu el the nlana. To have plaus accurate and
la aver wev reliable it nae oxen euiuaswu
there should be a long line ou the top, showing
the venation of the oompae at every time, so
by that maana 00 error oould well aria, now.
ar. the imnortano of aoourate blent la con
wiia with every deacripUoa of mining opera-
Hm nuna be too lorably aatirssssj. nor can
the beat known ay stem he too of tea brought
MINRKAW CONTAINING BILVKR.
Only a small proportion of th large amount
of silver which 1 at the present time produoed
for commercial purpose i found native, and
then not pure, as it it generally alloyed with a
little oopper, gold, platinum, mercury, araenlo,
iron, lead, bismuth or antimony.
Native silver occur In masses or ia arbor.
oeut and filiform ahapea ia vein traversing
gneiss, schists, porphyry, and other rooks It
also ocourt disseminated ia native oopper and
galena, but usually Invisible to th Baked eye,
therefor requiring th aid of a good micro
scop to determine it presence.
Silver when pur ha a matalllo luster. Color
and streak, silver white. Ductile, tlardnece,
2. 5. S. Hpecitlo gravity when pure, 10 5,
Minerals containing silver arc lounrt In veins ol
nearly all descriptions, and even ia lea water
minute trace hav been found by a careful
analysis.
Hilvsr la a metal extensively Used la th arte
and manufactures, and many product contain
more or lees proportions.
Silver will found In the pr-Huot a well
aa In th refut from nearly all lead and oopper
emelting work, if carefully looked for, and a
very email amount can be determined with
accuracy. Any mineral or- alloy containing
what ia called a "trace" of silver about on,
half ouooa to the ton of 8,000 tha, can b a,
eayed, and th metal extracted and determined
with accuracy.
Mr. Ueorgo Altwond. in hi "Practical Blow
ple Assaying," give the following list of prin
oipal mineral containing silver:
Argenlite, silver glance containing 87 ilwr,
with sulphur.
Htephenlte, brittle silver ore, oontalainl W
silver, with sulphur and antimony,
Prouetile, light red silver ore, containing
63.4 silver, with sulphur and arsenic
I'yrargyrile, dark red silver ore, containing
3U; silver, with sulphur and antimony.
Argentiferous grey copper or (fablers), con
Valuing from 5.7X to IV """i with
ttmony and sulphur.
Argentiferous aulphld of copper, containing
bi t silver, with sulphur and copper.
Polyhe.it, containing 7'J W,l atlvar, with
oopper, sulphur, araenio and antimony,
Uhilenite, containing tA., with biacaath
Ilromyril. oonlalnlog 07.1Z Mirer, witn
bromine fi
Carergyrtte (horn of ehlorwe), containing
'B 1
Kmholite, containing W-Tit aUver, with
bromine and oblurine,
Hternberiite. eootelalng i3.1l Silver, wilt
iron and sulphur H).
Imlynte, oouutuiog u silver, wivn woiae
Mi
Helenio silver, onuiaiug 11.0 i 00.0
silver, with selenium, copper and lead.
Ileeaite, containing sliver, Wlta leiia
rlum 37.2.
A law line of railroad la to be aonttnieted '
from the main Una of th Missouri-Pacific at th
pacific Junction, to Carthage, Mo, TBI Una
will open np a new and very rich ollo of Mi.
eouri and will shorten the through line to Text
by about 30 mile.
Aijvii'H front Pari say that La LihtrU aa
aooooee that CoL Walter' Trana-Hahara MUv
tioa will be taken an, and the murder ol Col.
KUlters and hi follower avenged. The aw
cxpodilioa will eoneiet of a regiment ol 700 mea
mounted oa oaroela.