Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 62
eel attachment, I, is tocarry the weight of the beam. The metal parts of this instru-ment occupy but little space. Lv#1<7 There are beam compasses in which the beam is graduated,and in which the boxes corresponding to B and C are fitted withvernier or reading plates, to afford the means of… … Fig. 142. Proportional dividers (Fig. 142), for copying and reducing drawings, arefound in most cases of instruments. Closing the dividers and loosening the screw C, the slide may be moved up 46 DRAWING INSTRUMENTS. in the groove until the mark on the index corresponds with the required num-ber ;…
Mechanical drawing
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