118 



MATHEMATICAL AND PHYSICAL SCIENCE. 



PISS. VI. 



which we owe to his genius. It is an analysis of the 

 coloured light of the (so-called) homogeneous rays of 

 the pure spectrum by the specific action of absorbing 

 substances. Sir D, Brewster believes that he has 

 separated the homogeneous orange of Newton into 

 red and yellow, the green into yellow and blue ; and 

 that, in fact, each of the three primary colours exists 

 at every point of the spectrum. But as grave doubts 

 have been thrown on the results, especially by the 

 recent careful experiments of "Helmholz, I shall not 

 further insist upon them here. l Still less can I take 

 notice of a multitude of microscopic researches on a 

 variety of objects in the animal, vegetable, and mineral 

 kingdom, and on the physiology of vision, with which 

 Sir D. Brewster has filled a multitude of memoirs, 

 each bearing testimony to the zeal and acuteness by 

 which his researches are directed. 



(542.) Sir David Brewster received, in 1816, jointly with 

 His other Seebeck, one of the great prizes of the Institute ; he 

 tific also received, in succession, all the medals in the gift 

 of the Royal Societies of London and Edinburgh, and 

 he is an honorary member of the principal academies 

 of Europe. In particular, he is one of the eight asso- 

 ciate-members of the French Academy of Sciences. 

 To meteorology he has been a valuable contributor, 

 having discussed in an able paper the law of the 

 distribution of temperature over the globe, and 

 pointed out the near coincidence of two regions 

 or centres of greatest cold in the northern hemi- 

 sphere, with the magnetic poles. His papers are 

 so numerous, and their variety is so great, as to 

 render an enumeration, even of those containing what 

 may reasonably be termed discoveries, impossible 

 within our limits. Few persons have made with 

 their own eyes so vast a number of independent 

 observations ; few have ever observed better, or re- 

 corded their observations more faithfully. He has 

 discovered (as we have partly seen) a multitude of 

 laws of phenomena of the greatest importance in the 

 construction of a theory, but he has not been forward 

 in proposing such a theory. Neither the moveable 

 polarization of Biot, nor the transverse undulations 

 of Young and Fresnel, received his cordial assent. 

 Generally speaking, he has been favourable to a cor- 

 puscular theory of light, without, however, attempting 

 to render the Newtonian view mechanically consistent 

 with the astonishing variety of complex phenomena 

 which he aided in discovering, and which would evi- 

 dently require it (to say the least) to be completely 

 remodelled. His scientific glory is different in kind 

 from that of Young and Fresnel ; but the discoverer 

 of the law of polarization, of biaxal crystals, of op- 

 tical mineralogy, and of double refraction by com- 

 pression, will always occupy a foremost rank in the 

 intellectual history of the age. 



(543.) Before closing this section I shall add a few words 

 respecting the discoveries of MM. Seebeck and Biot, 



which have a very close relation to those of Sir David 

 Brewster. 



THOMAS SEEBECK was born in 1770. We have (544.) 

 seen that he was one of the discoverers cf the depola- Seebeck. 

 rizing structure of heated and compressed glass (527). 

 In 1816 he observed, independently of M. Biot, the 

 property of oil of turpentine and other fluids to rotate 

 the plane of polarization of light transmitted through 

 them, thus acting similarly to a crystal of quartz on a 

 ray passing along its axis (512). Previously to these 

 discoveries he had repeated Sir William Herschel's 

 experiment on the position of maximum heat in the 

 spectrum, and found it to vary with the material of 

 the prism. When the science of electro-magnetism 

 was created by Oersted in 1819, his attention became 

 chiefly directed to that class of phenomena, and in 

 1823 he was fortunate enough to discover thermo- 

 electricity. He also wrote many papers on allied 

 subjects. He was a skilful observer, but deficient in 

 the power of physical analysis. He died in 1831. 



M. BIOT, at the time I write, the oldest member (545.) 

 (I believe) of the Academy of Sciences, and one of?** Blot 



\ ' n T-I i i T> BU name- 



the veterans ot European science, was born at Pans rous re _ 

 in 1774, and has lived to the age of 80, a life of searches, 

 almost unintermitted intellectual labour. It is im- 

 possible not to be touched by the evidence of such 

 unconquerable love of knowledge. He was, if I 

 mistake not, one of the original pupils of the Poly- 

 technic School ; and his talents being fii-st developed 

 in an almost purely mathematical direction, he at- 

 tracted the notice of Laplace, who introduced him to 

 the Institute, and by whom he was always befriended. 

 In 1802 he published a work on curves and surfaces 

 of the second degree, and was the first after Lambert 

 who thought of applying mathematics to the theory 

 of conducted heat. From this time his attention 

 was almost exclusively directed to the applied sciences, 

 and the number and variety of his experiments and 

 writings almost baffles enumeration. Descriptive and 

 practical astronomy, the theories of sound, of light, 

 of the voltaic pile, of terrestrial magnetism, of electro- 

 magnetism, of heat, radiant and combined, have been 

 the subjects of his studies and writings. We find him 

 in the earlier part of his career associated with Gay 

 Lussac in his first aeronautic expedition, and with 

 Arago in the geodetical and astronomical operations 

 of the great arc of the meridian. He afterwards 

 carried the pendulum to the Island of Unst, the 

 northmost land in Shetland ; and he made original 

 experiments on the propagation of heat and of sound. 

 He wrote a voluminous treatise on descriptive and 

 practical astronomy, one still more elaborate on 

 general physics, and a vast number of miscellaneous 

 papers in the Journal des Savans and the Biographic 

 Universelle. His original memoirs in the Trans- 

 actions of the Academy are usually very long and 

 elaborate, his calculations and empirical formulae 



1 See Sir D. Brewster's statement and defence of his opinions in his Life of Newton, vol. i., p. 117, &c. 



