en. XXXII. DR. THOMAS YOUNG. 303 



two different theories of light (see page 174). Newton's, 

 called the Corpuscular or Emission Theory, supposed light to 

 be made up of minute particles darting out from the sun and 

 every light-giving body. Huyghens, on the contrary, taught 

 that light is produced by the vibrations or waves of an in- 

 visible ether which is supposed to fill all space. This was 

 called the Undulatory or Wave Theory. 



Newton's authority was so great, and the experiments he 

 made to prove his theory were so striking, that the * Corpus- 

 cular theory ' was generally received as the true one, espe- 

 cially as Huyghens had only made a few simple experiments 

 in support of his idea ; and it was more than a hundred 

 years after Huyghens first published his * Treatise on Light ' 

 before a man arose to defend the Undulatory theory and to 

 bring it again into notice. This man was Dr. Thomas Young, 

 the first Professor of Natural Philsophy at the Royal Insti- 

 tution of London. 



Thomas Young, who was the son of a Quaker, was born 

 at Milverton, in Somersetshire, in 1773, and died in 1829. 

 He was brought up at home, and seems to have been a very 

 clever lad, for he knew seven languages at the age of four- 

 teen, besides having studied Natural Science as an amuse- 

 ment. He then went to the Edinburgh University, where he 

 worked under dear old Dr. Black, whose enthusiasm, no 

 doubt, helped much to increase his love of science. When he 

 was only twenty he sent a paper on * Vision ' to the Royal 

 Society, and was elected a member the following year. He 

 then went to Cambridge in order to be able to satisfy the 

 College of Physicians, and practised as a medical man in 

 London, where, in 1 801, he was also made Professor of 

 Natural Philosophy at the Royal Institution, which had just 

 been founded, and Editor of the Nautical Almanack He is 



