JOULE 291 



regarded as setting an example of the highest accuracy of 

 measurement. 1 



James Prescott Joule was born at Salford near Manchester, 

 being the second son of a brewer. The brewery was a 

 family business, and had been founded by his grandfather. 

 James Prescott was a weakly child, and was brought up en- 

 tirely at home until his fifteenth year, when he began to 

 work in the brewery, but at the same time received, together 

 with his older brother, instruction in mathematics and 

 science from Dalton. Immediately afterwards he also 

 began to experiment himself, mainly with home-made ap- 

 paratus, for which purpose he found room in his father's 

 house. At the age of nineteen he wrote his first published 

 paper, concerning a new kind of electric motor, which how- 

 ever he soon himself recognised to be of no advantage; at 

 twenty-two his first publication on the production of heat 

 by electric current followed. His father later built for him 

 a laboratory. After he and his brother had taken over the 

 brewery, he married, but his wife died in 1854, in which 

 year the brewery, so far under his direction, was sold. From 

 that time onwards he lived in great retirement, entirely de- 

 voted to his scientific work. From the year 1872 onwards 

 his health was poor; from 1878 he received a pension from 

 the Queen. He died at the age of seventy-one, at his birth- 

 place, Salford. 



Joule, like Faraday, had the rare good fortune to find in his 

 youth a teacher who was worthy of him; in Faraday's case 

 it was Davy, in Joule's, Dalton. Neither of them went 

 through a special course of training 'in their science,' any 

 more than almost all other great men of science; they 

 produced their own science. In Joule's case we get the 



1 Later and still more refined measurements (which gave the value 427 

 mkg/cal) could only be carried out when the fundamental unit of heat, 

 the calorie, had been more exactly defined, but this of course is only 

 important in cases where the accuracy reached is of a most unusual 

 description. 



