82 The Arithmometer. 



Art. XVIII. — A Universal Equatorial and an Instrument 

 for Facilitating the Observation of Mars. 



By T. Harrison, Esq. 



[Read 6tli September, 1875.] 



Art. XIX.— The Arithmometer. 

 By W. C. Kernot, Esq., M.A 



[Read 6tli September, 1875.] 



The machine to which I propose to invite your attention 

 this evening is the invention of M. Thomas de Colmar, and 

 is termed by him the Arithmometer, or number measurer. It 

 was first patented in 1820. In 1822 the inventor exhibited 

 it to the Societe d'Encouragement pour l'lndustrie Nationale. 

 In 1851 the gold medal of that society was awarded to the 

 inventor, and one of the instruments was exhibited at the 

 Great Exhibition at London of that year ; but, as far as I 

 can judge from the published records of that exhibition, 

 does not appear to have been so complete as those of 

 more recent construction. The first machine that reached 

 this colony, as far as I am aware, was imported by 

 J. M. Templeton, Esq., F.I.A., about three years ago. On 

 inspecting Mr. Templeton's machine I became convinced of 

 its utility, and immediately ordered one, which you now see 

 before you. This instrument I have had in constant use for 

 more than two years, with the most satisfactory results. 



The diagram accompanying this paper represents the 

 upper surface or " face " of the instrument, which consists of 

 two plates of brass, A A and B B. The plate A, which is 

 permanently fixed, is pierced by a series of slots, in each of 

 which is placed a metal button capable of motion from one 

 end of the slot to the other. At the side of each slot the 

 numbers 1 to 9 are engraved on the plate. Immediately 

 beneath each slot there is a square horizontal steel axis, 

 upon which a pinion of ten teeth is capable of sliding 

 longitudinally. This pinion is connected with the button, 

 so that its position on its axis will vary when the button is 

 moved. Below the pinion there is a drum or cylinder, 

 having nine teeth of successively diminishing length, so 



