Mr. J. Edmondson on Calculating Machines. 17 



make an independent note of it until it can be dealt with. 

 Each dial has a tooth (the primary carrying-tooth) which 

 makes this note at the moment that the dial passes from 9 to 

 0, by pushing along the axis of the reckoner belonging to the 

 next higher digit a sliding-piece which revolves with the 

 reckoner and carries a single tooth (the secondary carrying- 

 tooth). Above this sliding-piece, and upon the same axis as 

 the pinion in gear with the reckoner, is a second pinion of 

 10 teeth. Before the sliding-piece was moved by the primary 

 carrying-tooth, the secondary carrying-tooth passed on the 

 side of this second pinion without affecting it ; but being now 

 brought into line with it, the pinion will be moved 1 tooth, 

 and will therefore add 1, as soon as the reckoner has added its 

 own proper number ; so that the fourth revolution, giving the 

 product of 33,333,333 by 4, brings the dials to 133,333,332. 

 When the secondary tooth has done its work, an incline on 

 its side comes in contact with a projection on the frame of the 

 machine, which restores it to its original inoperative position. 

 Each reckoner is set to operate a little later than its neighbour 

 to the right, so that the carrying on the latter may be com- 

 pleted before that on the former is commenced. The before- 

 named blank space on the reckoner is to allow time for the 

 carrying ; and for a " dead-point " in the machine, at which 

 the first-named pinions, which are movable longitudinally on 

 their axes, may be set to their required sections of the reck- 

 oners, and other changes may be made in the setting of the 

 machine. The position of the pinions is shown by indicators 

 on the face of the machine, each of which can be set to any 

 required figure. 



Each pinion communicates its motion to its dial by bevel- 

 gear in the well-known combination of three wheels, which 

 permit the action to be reversed at will, so that the change 

 from + to — or from x to h- is made instantaneously. 



In multiplying by more than a single digit, the dials require 

 to change their position in relation to the multiplicand, to 

 imitate the " stepping " of the lines in long multiplication. 

 They are therefore placed in a slide which can be moved, step 

 by step, from right to left or vice versa. 



Up to a recent date the machine of M. Thomas de Colmar 

 was the only one in use. A few years ago Mr. George B. 

 Grant, of Boston, Mass., brought out an instrument somewhat 

 on the lines of the Stanhope machine of 1777. It is very 

 compact, is beautifully and substantially made ; but as sub- 

 traction is performed by adding the complement of the 

 subtrahend, reversing is so tedious as to be fatal to the 

 general adoption of the machine. Its range is also very 



Phil. Mag. S. 5. Vol. 20. No. 122. July 1885. C 



