I. GEOMETRICAL DRAWING. 19 



69g. Patent Compasses, with drawing pen and leaden tube. 

 E. O. Richter and Co., Chemnitz, Saxony. 



69h. Patent Diamond Compasses, for lithography. 



E. 0. Richter and Co., Chemnitz, Saxony. 



69i. Patent Diamond Compasses with drawing pen, for 

 lithography. E. O. Richter and Co., Chemnitz, Saxony. 



69j. Patent Hatching Ruler (for shading by cross-lines in 

 drawing and engraving). 



E. 0. Richter and Co., Chemnitz, Saxony. 



A ruler is attached to a cylinder which, rolling on a plate, draws the 

 former after it. By means of an endless screw, working in a wheel, the 

 cylinder is moved forward. A cogwheel is attached to the endless screw, 

 in which a bar catches, and by the depression of which the mechanism is 

 put in motion. The depression can be regulated by a screw, by which means 

 the various distances of the lines are obtained. One finger is sufficient for 

 working the ruler by simply pressing on the screw, and holding it until 

 the line is drawn. 



69k. Six Setter Diamonds, for lithography. 

 691. Five Machine Diamonds, for lithography. 



69m. Six Scratching Diamonds, for lithography. 



E. O. Richter and Co., Chemnitz, Saxony. 



69n. Perspectograph. Lieut. -General M. W. Smith. 



This instrument is employed to determine the perspective position of a 

 point on the surface of a picture corresponding to any point in nature, the 

 actual position of which is ascertained by means of ground plans, elevations, 

 sections, actual measurement, or otherwise, or else assumed in the composi- 

 tion of a picture. A horizontal line is drawn across the picture and a point 

 assumed upon it to represent the point or centre of view, the perspective point 

 (the two ordinates, of which one parallel and the other perpendicular to 

 the horizontal line are determined by the instrument) is then laid down from 

 the point of view by scale and offset. The manipulation of the instrument is 

 very simple and easily acquired ; and as the perspective representation of any 

 number of points, constituting lines, planes, solids, &c., can be rapidly 

 transferred to the picture, the most complicated problems of perspective, 

 whether rectangular or oblique, can be performed without lines of geometrical 

 construction, or the transferrence of the subject from a plan previously pre- 

 pared to the picture. A detailed description of the working of these instru- 

 ments, as well as of the system upon which their construction depends, will be 

 found in " Engineering," 1876. 



69o. Pointfinder. Lieut.- General M. W. Smith. 



This instrument is used in sketching from nature and is employed to 

 determine a point on the surface of the picture corresponding to any point in 

 nature to which the sights of the instrument may be directed, as follows : 

 Having drawn a line horizontally across the paper to represent the horizontal 

 line, and assumed a point upon it as the point of view, the instrument is set to 

 zero both on the horizontal, and side vertical graduated arcs ; and levelled by 

 means of the small plumb bob, the sights being at the same time upon any 



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