MB. BABBAGE'S CALCULATING MACHINE. 295 



done in such a manner as effectually to prevent 

 any accumulation of small errors from producing 

 an erroneous figure in the result. 



In order to convey some idea of this stupend- 

 ous undertaking, we may mention the effects pro- 

 duced by a small trial engine constructed by the 

 inventor, and by which he computed the following 

 table from the formula # 2 +#+41. The figures, 

 as they were calculated by the machine, were not 

 exhibited to the eye as in sliding-rules and similar 

 instruments, but were actually presented to the 

 eye on two opposite sites of the machine, the 

 number 383, for example, appearing in figures 

 before the person employed in copying. 



Table calculated by a small Trial Engine. 

 41 131 383 797 1373 



43 151 421 853 1447 



47 173 461 911 1523 



53 197 583 971 1601 



61 223 547 1033 1681 

 71 251 593 1097 1763 

 83 281 641 1163 1847 

 97 313 691 1231 1933 

 113 347 743 1301 2021 



While the machine was occupied in calculating 

 this table, a friend of the inventor undertook 4o 

 write down the numbers as they appeared. In 

 consequence of the copyist writing quickly, he 

 rather more than kept pace with the engine, but 

 as soon as five figures appeared, the machine was 

 at least equal in speed to the writer. 'At another 

 trial thirty-two numbers of the same table were 

 calculated in the space of two minutes and thirty 

 seconds ; and as these contained eighty-tivo figures, 



