Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 209
ringof a line proceed as fol-lows : Place the compassso that the Jacobs staff,or plummet of the tripod,is directly over one end ofthe line, and level by press-ing with the hands on themain plate until the bub-bles are brought to thecentres of the spirit levels.Turn the south end of the instrument… … Fig. 9 FIELD INSTRUMENTS 221 of the compass circle; secondly, write the number of degreesbetween the north end of the needle and the nearest zero mark ;thirdly, write E. or W. according as the north end of the needleis nearer E. or W. of the compass circle. Thus, in Fig. 9 (a), thebearing is N. 45°…
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![An illustration from Divina proportione : opera a tutti glingegni perspicaci e curiosi necessaria oue ciascun studioso di philosophia: prospettiua pictura sculptura: architectura: musica: e altre mathematice: suavissima: sotile: e admirabile doctrina consequira: e delecterassi: co[n] varie questione de secretissima scientia (1509)](https://img.insideoutlibrary.com/img/200/ia-divinaproportion00paci-105-254.webp)
