. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . nts a h equal 10 in., dividedinto tenths, and if the micrometerscrew divides ^ of an inch into100 equal parts, then the = 10000 ; such equal partsand the difference of the tangentsof the two observed angles at aand Ò may be found to be ^„¿q,^of an inch = • 0001 = 20 • 6 greater accuracy be required,and a -^ vernier be applied tothe micrometer screw, then theradius is taken = 100000 equalparts, and the tangents are mea-sured to ^ „ „\)

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. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . nts a h equal 10 in., dividedinto tenths, and if the micrometerscrew divides ^ of an inch into100 equal parts, then the = 10000 ; such equal partsand the difference of the tangentsof the two observed angles at aand Ò may be found to be ^„¿q,^of an inch = • 0001 = 20 • 6 greater accuracy be required,and a -^ vernier be applied tothe micrometer screw, then theradius is taken = 100000 equalparts, and the tangents are mea-sured to ^ „ „\) ,j „ of an inch =•00001 = tangent of 2 nearly. The principle uj)on which theinstrument. Fig. 3378, works maybe shown as follows ;— Let Ö = ^ of observation atthe higher level, as c, Fig. 3379 ;Q = Z. observed angle at thelower elevation, hdc; r = sd, thelength of the vertical bar a 6,Fig. 3378 ; E = (7 6, the horizontalrange ; c the position of theenemys battery ; then sd . b c .. do . ob ; .. sdì (^sd+bc) .. do : (^do+ob). Since sd = ab, we have (tan. 6— tan. 0) : tan. 0 : : r cotan. 0 : R ; tan. 0 cotan. 0 ^. 3330.

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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering