BALFOUR STEWART. 375 



Helmholtz, already quoted, writes : " Whether life in Berlin is 

 favorable to scientific pursuits may well be doubted. The teacher, it 

 is true, gains a wider, richer field of activity, but the investigator is 

 robbed of a larger part of his time. Kirchhoff, however, was protected 

 by his physical disability against most of the drive of the capital, and 

 was able to labor as he had usually done." 



In his power of handling physical problems, Professor Tait ranks 

 him as the compeer of H. L. F. Helmholtz, Stokes, Sir William Thom- 

 son, and Clerk Maxwell. His discovery of spectrum analysis is an 

 epoch-making one in science, felt equally in the humblest chemical 

 analysis and in the remotest star and nebula. 



BALFOUR STEWART. 



To have achieved a permanent place in the literature of physics is 

 no small achievement. This honor we feel that the world will accord 

 to Professor Balfour Stewart. He was born in Edinburgh on Novem- 

 ber 1, 1828, and died on December 18, 1887. He pursued his studies 

 at the Universities of St. Andrews and Edinburgh. Unlike most men 

 who have devoted themselves to science, he did not linger in the shade of 

 university walls, but began life in a mercantile office. It is said that his 

 leaning toward physical science first strongly manifested itself on a busi- 

 ness voyage to Australia, thus affording another instance of the effect of 

 solation, so characteristic of sailing voyages, upon a philosophic tem- 

 perament. His first scientific papers were published in the Transactions 

 of the Physical Society of Victoria, in 1855, at the age of twenty-seven, 

 and were entitled "On the Adaptation of the Eye to different Rays," 

 and " On the Influence of Gravity on the Physical Condition of the 

 Moon's Surface." It is curious to notice that these early papers were 

 upon the subjects which were destined to engross his attention in ma- 

 ture life, — the subjects of light or radiant energy in general, and the 

 effect of gravitation potential ou the physical properties of matter. 

 Shortly after his return from Australia, he abandoned business pursuits 

 and became the assistant of Professor Forbes. In 1858 he enunciated 

 his extension of Provost's Law of Exchanges, and had the good fortune 

 to express one of the great laws of nature in so simple a manner, and 

 with such convincing proofs from his own investigations, that the future 

 student will always connect it with the name of Balfour Stewart. Pre- 

 vost had shown that a hot iron ball, for instance, surrounded by other 

 objects, gained or lost heat in proportion to the absorbing and radiating 

 power of the iron and the neighboring objects. Its temperature might 



