132 Britain's Heritage of Science 



reasonable limits. Even when Fizeau had made his crucial 

 experiment and shown that the velocity of light in ordinary 

 refracting bodies was smaller than in air and not greater, as it 

 should be according to the corpuscular theory, Brewster 

 refused to admit the validity of the evidence. 1 Nevertheless, 

 Brewster was a great experimenter, though an unkind 

 Nemesis turned his most important investigations into an 

 armoury which supplied effective weapons to his opponents. 

 He studied the laws of polarization by reflexion and refraction 

 both for transparent and metallic media; he discovered 

 the connexion between the refractive index and polarizing 

 angle, and the double refraction due to strain. He also first 

 examined crystalline plates under the polariscope in diverging 

 light. He was a prolific writer, and contributed many articles 

 to the early editions of the " Encyclopaedia Britannica." He 

 is said to have given the first impulse to the foundation of 

 the British Association, and was one of its chief supporters 

 during the first years of its existence. 2 



While Brewster was battling in vain against the tenets of 

 modern physics, a young Scotsman, equally distinguished 

 as an experimenter, but superior in judgment and scientific 

 insight rapidly rose to eminence. James David Forbes 

 (1809-1868) was the fourth son of Sir William Forbes, 

 seventh baronet of Pitsligo. He entered the University of 

 Edinburgh at the age of sixteen, and soon afterwards con- 

 tributed anonymously to the Edinburgh Philosophical Journal. 

 At the age of twenty -three, which even then must have been 

 a quite exceptionally early age, he was elected a Fellow 

 of the Royal Society. In 1833 he was appointed Professor 

 of Natural Philosophy at Edinburgh University in succession 

 to Sir John Leslie, Sir David Brewster being the com- 

 peting candidate, and in 1859 he succeeded Brewster in the 



1 The authority for this statement is an oral communication by 

 Stokes. 



2 In the " Encyclopaedia Britannica," eleventh edition, it is stated : 

 " In an article in the ' Quarterly Review,' he threw out a suggestion 

 for ' an association of our nobility, clergy, gentry and philosophers * 

 which was taken up by others, and found speedy realisation in the 

 ' British Association for the Advancement of Science.' " No such 

 article can be found hi the " Quarterly Review." 



