20 Britain's Heritage of Science 



might still show different effects, for if the wave comes 

 straight towards us the direction of motion might be hori- 

 zontal or vertical. 



If the originality of a discovery can be gauged by the 

 opposition it rouses, Young's work takes a high rank. In 

 referring to his explanation of the interference of light 

 (Edinburgh Review, Vol. I., p. 450) Lord Brougham 

 expresses the opinion that it " contains nothing which 

 deserves the name either of experiment or discovery," 

 and concludes by " entreating the attention of the Royal 

 Society, which has admitted of late so many hasty and 

 unsubstantial papers into its Transactions." 



As regards the suggestion of transverse vibrations, one 

 might have imagined that the analogy of water waves 

 would have secured its being more readily accepted, but 

 the passage from two to three dimensions is by no means 

 obvious, and its difficulties presented themselves with 

 special force to mathematicians. When Fresnel had inde- 

 pendently recognized that the experimental facts could 

 not be explained except by accepting this transverse 

 motion, he placed the wave theory of light on a new 

 and firm basis ; but he lost the collaboration and sympathy 

 of his colleague Arago, who, up to the time of his death 

 in 1853, would not recognize the possibility of a spherical 

 wave in which the motion was not entirely radial. Even 

 Laplace and Poisson were strongly antagonistic to the idea 

 of spherical waves with transverse displacements ; their 

 difficulty was a very substantial one, solved only at a later 

 date by the investigations of Stokes. 



Of all men who have spent their lives in the search for 

 experimental discoveries, no one has ever approached 

 Michael Faraday (1791-1867) in the number, the variety, 

 or the importance of the new facts disclosed by his labours. 

 If we wish to select from among these discoveries one or 

 two which have had a predominant influence in directing 

 scientific efforts into new channels, we must give the first 

 place to his researches on electro -magnetic induction. 

 Starting from the discovery that an electric current suddenly 

 generated or suddenly stopped caused an instantaneous 

 current in a wire placed in its neighbourhood, he proceeded 



