Image provided by: University of Oregon Libraries; Eugene, OR
About The west shore. (Portland, Or.) 1875-1891 | View Entire Issue (May 1, 1881)
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.