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APPENDIX. 



24b. Cabinet, containing tablets for making mathematical 

 calculations. Archaeological Museum, Madrid. 



Rose wood cabinet, inlaid with ivory. In three divisions are thirty small 

 drawers, containing ivory plates with numbers and divisions to make mathe- 

 matical calculations. In the inside are the arms of the monastery of the 

 Escorial. Milanese work of the 16th century. 



28b. Original Calculating Machine, known as " Napier's 

 Bones." Lord Napier and Ettrick. 



One of the earliest attempts to construct a calculating machine, made by 

 John Napier, the inventor of logarithms. His method of calculating by rods 

 was published in a volume, (which is exhibited with the machine) at Edin- 

 burgh in 1617. The apparatus was commonly known as " Napier's Bones." 



69e. Patent Dotting Pencil. 



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



The arrangement is as follows : 



A small toothed wheel adapted to the kind of dotted lines to be drawn is 

 attached to a plate, which, rolling on the paper, lifts a lever, which is again 

 dropped by means of a spring. Attached to this arm is a drawing-pen, easily 

 adjustable, by means of a hinge, to the correct position suited to the wheel. 

 The wheel itself is held in position by a small, somewhat elastic plate, which 

 can be displaced a little for fitting the different reserve wheels on which 

 the kind of lines to be drawn depends. 



69f. Patent Compasses with stationary centre point. 



E. O. Richter and Co., Chemnitz, Saxo n y. 



These compasses differ from others, chiefly by the centre-point being 

 stationary on the paper, so that the tracing-pen, resting on the paper by its own 

 gravity, moves about the centre-point as axis, whilst the movable pen can be 

 displaced, without removing the compasses from the paper. By these advan- 

 tages speedy and neat tracing will be achieved, even when the smallest circles 

 are to be drawn. 



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

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



69h. Patent Diamond Compasses. 



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



69i. Patent Diamond Compasses with drawing pen. 



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



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