CH. XIII] CALCULATING PRODIGIES 279 



and Mitchell, but they seem to have been typical of these calcu- 

 lators. In 1842, he amused and astonished his family by mental 

 calculations. In 1846, when ten years old, he was examined, 

 and here are some of the questions then put to him : — Extract 

 the cube root of a certain number of seven digits; answered 

 instantly. What number is that which being divided by the 

 product of its digits, the quotient is three, and if 18 be added 

 the digits will be inverted : answer 24, given in about a minute. 

 What is the surface of a regular pyramid whose slant height is 

 17 feet, and the base a pentagon of which each side is 335 feet : 

 answer 3354'5558 square feet, given in two minutes. Asked to 

 square a number of eighteen digits he gave the answer in a 

 minute or less, but the question was made the more easy as the 

 number consisted of the digits 365 repeated six times. Like 

 Colburn he factorized high numbers with ease. In such 

 examples his processes were empirical, he selected (he could 

 not tell how) likely factors and tested the matter in a few 

 seconds by actual division. 



There are to-day four calculators of some note. These are 

 Ugo Zamebone, an Italian, born in 1867 ; Pericles Diamandi, a 

 Greek, born in 1868 ; Carl Riichle, a German ; and Jacques 

 Inaudi, born in 1867. The three first mentioned are of the 

 normal type and I do not propose to describe their perform- 

 ances, but Inaudi's performances merit a fuller treatment. 



Jacques Inaudi* was born in 1867 at Onorato in Italy. He 

 was employed in early years as a sheep-herd, and spent the long 

 idle hours in which he had no active duties in pondering on 

 numbers, but used for them no concrete representations such as 

 pebbles. His calculating powers first attracted notice about 

 1873. Shortly afterwards his elder brother sought his fortune 

 as an organ grinder in Provence, and young Inaudi, accom- 

 panying him, came into a wider world, and earned a few coppers 

 for himself by street exhibitions of his powers. His ability 

 was exploited by showmen, and thus in 1880 he visited Paris 



* See Charcot and Darboux, MSmoires de Vlnstitut, Comptes Bendus, 1892, 

 vol. cxiv, pp. 275, 528, 578 ; and Binet, Iiivue des deux Mondes, 1892, vol. oxi, 

 pp. 905—924. 



