Canadian engineer . ns are required. By con-vention the left station may be conveniently taken as thepoint from which measurements are to be made, hence theco-ordinates x and y will be measured from the left plateand the parallax from both. It now remains to show how the actual co-ordinates ofa point in space may be determined from the co-ordinatesas measured on the stereograph. In Fig. 3 : Let P be the point whose position is to be determinedand which is represented on the plates by the images P, andPj-, let the ordinates of these points be x and x^, (x beingnegative), let B be the base and f
Canadian engineer . ns are required. By con-vention the left station may be conveniently taken as thepoint from which measurements are to be made, hence theco-ordinates x and y will be measured from the left plateand the parallax from both. It now remains to show how the actual co-ordinates ofa point in space may be determined from the co-ordinatesas measured on the stereograph. In Fig. 3 : Let P be the point whose position is to be determinedand which is represented on the plates by the images P, andPj-, let the ordinates of these points be x and x^, (x beingnegative), let B be the base and f the focal length of thelens. Then, from similar triangles it is evident that Z the f f distance of a 1 lane through P = B —?——, = B — also X = and Y = X -f- x X Z— f y z— f mirrors Mi and Mo. Each pdate may be rotated in its owqplane by screws Si and So, so that the horizons of the twoplates may be accurately adjusted. Also, the right plate P,may be moved parallel to its length by the screw H so as to. Fig. 3. compensate for difference in level of the two stations. In theoptical planes of the microscope are two balloon marks whichappear to coincide when the instrument is in accurate adjust-ment and may be set so as to apparently coincide with anypoint on the stereograph whose position is required. March 28, 1912. THE CANADIAN ENGINEER 451 The screw A moves the entire bed plate, carrying- bothphites to the right or left, and its movement is indicated onthe scale X. the screw B moves the microscope at rightangles to the bed plate, and its motion is indicated in thescale Y, and the screw C moves the right to the rightor left independently of the other plate, and its movement isindicated by a scale and divided screw head Z. All threescales read to 1/50 mm., and by estimation to i/ioo , by means of the scale X the distance of any poinfto-left ( + ) or right (—) of the optic axis is measured bymeans of Y the heig-ht of any point above ( + ) or its depthbe
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishertoron, bookyear1893
