Addition ofNumlers iiilh Accuracy and Dispatch. 167 



by the Society of Arts, &c. published in the year I8O9. 

 After I had read of those honorarr and pecuniary rewards 

 which had been given, and were then offered, my desire 

 to obtain sonie mark of the Society's approbation could 

 no^ be appeased but by possession, and I was determined 

 to cairv niv idea into execution; I immediately renewed 

 my study of this instrument with increased application. 



Ca^tuio; up bills is what falls to the lot of most people 

 in business, and many who are moderately clever at it often 

 find it a troublesome ta^k before they can place any depen- 

 dence on their being right ; they have need to cast them 

 up two or three times, and even then have often as many 

 different sums, and therefore frequently find themselves 

 much confused and puzzled in the operation : the instru- 

 ment of my invention in such cases would be very accept- 

 able : it would take the work from the mind, and give it to 

 the hand, which would perform it with greater ease, accu- 

 racy, and expedition ; a person who can only read figures, 

 may bv this help add up a bill with as much accuracy as a 

 mathematician. 



The same day I completed my instrument, I showed it 

 to the people with whom I lodged, who as I have already 

 observed were shop-keepers. I wrote a bill, and desired 

 them to cast it up; I then showed them how io do it by 

 my wheel, and desired them to add up the same bill by it, 

 and see if it was ris;ht. They then proceeded, and cast it 

 up right by the wheel, when they discovered that they had 

 made a mistake of one shilling in the row of pence, and 

 two shillings in the row of shdlings. They were therefore 

 much pleased with my new contrivance, because it was 

 more true and hss troublesome than the common way. 



This wheel has four circular rows of figures upon its 

 face. The first row which is nearest the teeth on the cir- 

 cumference, denotes pence, the second shillings, and the 

 third and fourth denote the total number of pence or shil- 

 lings, &c. Thus, if 64 in the third row should be under 

 the index, if I were casting up pence, I should see in the 

 first row, 4 under or next before the index, and the next 

 red figure passed over by the index would be 5, which 

 signify 5$. 4d., (he red figure or figures nearest the index 

 signifying shillinijs, and the black figure or figures before 

 the index the odd pence. In the second row, the black 

 figure before ihe index signifies the number nf odd shil- 

 lings, and ihe next red figure the numl)er of pounds. Be- 

 fore I begin to work, the red figures 360, 180, 9, 15, must 

 always be placed next before the index. 1 then begin to cast 

 L 4 up 



