754 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



son before his journey to England. On August 6 he wrote to Frau 

 Helmholtz that Thomson had made a deep impression on him. 



I expected to find the man, wbo is one of the first mathematical physicists of 

 Europe, somewhat older than myself and was not a little astonished when a 

 very juvenile and exceedingly fair youth who looked quite girlish came for- 

 ward. He had taken a room for me close by and made me fetch my things 

 from the hotel and put up there. He is at Kreutznach for his wife's health. 

 She appeared for a short time in the evening, and is a charming and intel- 

 lectual lady, but is in very bad health. He far exceeds all the great men of 

 science with whom I have made personal acquaintance, in intelligence, and 

 lucidity, and mobility of thought, so that I felt quite wooden beside him some- 

 times. 



A year later Helmholtz again met the Thomsons at Schwalbach. 

 Writing to his father, he described Thomson as " certainly one of the 

 first mathematical physicists of the day, with powers of rapid inven- 

 tion such as I have seen in no other man." In 1860, after the death 

 of Mrs. Helmholtz, the great German j)hilosopher again visited Brit- 

 ain, staying with the Thomsons for some weeks in the island of 

 Arran. In 18G3 Helmholtz, who in the meantime had married again, 

 came to England and visited the chief universities, and in writing to 

 his wife gives an amusing picture of his doings. 



My journey to Glasgow went off very well. The Thomsons have lately moved 

 to live in the university buildings (the old college) ; formerly they spent more 

 time in the country. He takes no holiday at Easter, but his brother James, pro- 

 fessor of engineering at Belfast, and a nephew who is a student there, were 

 with him. The former is a level-headed fellow, full of good ideas, but cares for 

 nothing except engineering, and talks about it ceaselessly all day and all night, 

 so that nothing else can be got in when he is present. It is really comic to see 

 how the two brothers talk at one another and neither listens, and each holds 

 forth about quite different matters. But the engineer is the most stubborn, and 

 generally gets through with his subject. In the intervals I have seen a quantity 

 of new and most ingenious apparatus and experiments of W. Thomson, whicli 

 made the two days very interesting. He thinks so rapidly, however, that one 

 has to get at the necessary information about the make of the instruments, etc., 

 by a long string of questions, which he shies at. How his students understand 

 him without keeping him as strictly to the subject as I ventured to do is a 

 puzzle to me ; still there were numbers of students in the laboratory hard at 

 work, and apparently quite understanding what they were about. Thomson's 

 experiments, however, did for my new hat. He had thrown a heavy metal 

 disk into very rapid rotation, and it was revolving on a point. In order to show 

 me how rigid it became on rotation he hit it with an iron hammer, but the disk 

 resented this, and it flew off in one direction and the iron foot on which it was 

 revolving in another, carrying my hat away with it and ripping it up. 



But we are anticipating. Hitherto Thomson's work had been 

 mainly in pure science; but toward the end of the fifties, while still 

 in the midst of thermodynamic studies, events were progressing which 

 drew him with irresistible force toward the practical applications 

 that made him famous. Indeed, it could hardly be otherwise, seeing 



