File:Transactions (1871) (14596623690).jpg

Identifier: transactionsmining31amer (find matches)
Title: Transactions
Year: 1871 (1870s)
Authors: American Institute of Mining, Metallurgical, and Petroleum Engineers
Subjects: Mineral industries
Publisher: New York (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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meter of youre instrument representing themeridiane) equal I to the variation of the copasse in your region : which in Eng-land is 11^ grades or neere therabout, and may be redely observed in all placessundrie waves. But thereof I mind not here to entreate, forasmuch as it apper-tayneth to Cosmographie & navigatio, whereof I haue copiled a treatise by itself,touching the fabricatio this may suffise. 84 NOTES ON MINE-SURVEYING (NSTRUMENTS. His 30th chapter begins: />// this instrument to know how many myles or pass any shippe is distcmte from you,your stlft standing vpon an highs diffi or platforms by th> sea coasts, Your topographical) instrument eqnedistantly situate to the Horizon, (as wasbefore declared I tnrne the diameter of the semicircle towards the ship, etc. It is perfectly clear from the figure (Fig. 154), as well as thetext, that the instrument is nothing but the modern theodolite;except that it is rudely made, and that it has sights for the Fig. 154. n**^^<^S;
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Diggess Topograph icall Instrument in Use. naked eye in place of the refracting telescope not then invented.The vertical semicircle is joined to the sights just as it is inthe modern theodolite to the telescope, but is supported by apillar from the center of the horizontal plate, instead of bytwo standards or vees; and the pillar is joined to the alidadeinstead of to a vernier plate. To see the essential identity, itis only necessary to compare the figure with Figs, 16 and 17,pp. 696 and 698, vol. xxviii. of the Transactions. To be sure,the square geometricall has been disused in the modernform, and the graduated plate is round. \.-i H OS mini 91 i:\ iITINQ ENS! 1:1 KBN I Digg< - i icpresslj mentions the application of his instrumentto underground use. meaning particularly military mines, atthe end of the 85th chapter and of the M ryrst Booke, as fol-low - : I Nott • M • Bloat oommodioasly fclso serueth this instrument to oooducte Myu< - rndertbeearth, for noting the Angles

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