268 CALCULATING PRODIGIES [CH. XIII 



multiplications by 5 and 20 are equivalent to a multiplication 

 by 100, of which the result can be at once obtained. Of 

 billions, trillions, &c, he had never heard, and in order to 

 represent the high numbers required in some of the questions 

 proposed to him he invented a notation of his own, calling 10 18 

 a tribe and 10 36 a cramp. 



As in the case of all these calculators, his memory was 

 exceptionally good, and in time he got to know a large number 

 of facts (such as the products of certain constantly recurring 

 numbers, the number of minutes in a year, and the number 

 of hair-breadths in a mile) which greatly facilitated his calcu- 

 lations. A curious and perhaps unique feature in his case was 

 that he could stop in the middle of a piece of mental calculation, 

 take up other subjects, and after an interval, sometimes of 

 .veeks, could resume the consideration of the problem. He 

 could answer simple questions when two or more were proposed 

 simultaneously. 



Another eighteenth-century prodigy was Thomas Fuller, a 

 negro, born in 1710 in Africa. He was captured there in 1724, 

 and exported as a slave to Virginia, U.S.A., where he lived till 

 his death in 1790. Like Buxton, Fuller never learnt to read 

 or write, and his abilities were confined to mental arithmetic. 

 He could multiply together two numbers, if each contained 

 not more than nine digits, could state the number of seconds 

 in a given period of time, the number of grains of corn in a 

 given mass, and so on — in short, answer the stock problems com- 

 monly proposed to these prodigies, as long as they involved only 

 multiplications and the solutions of problems by rule of three. 

 Although more rapid than Buxton, he was a slow worker as 

 compared with some of those whose doings are described below. 



I mention next the case of two mathematicians of note who 

 showed similar aptitude in early years. The first of these was 

 Andre Marie Ampere, 1775 — 1836, who, when a child some four 

 years old, was accustomed to perform long mental calculations, 

 which he effected by means of rules learnt from playing with 

 arrangements of pebbles. But though always expert at mental 

 arithmetic, and endowed with a phenomenal memory for figures, 



