3 , 6 NINETEENTH CENTURY. rr. in. 



Newton's, called the Corpuscular or Emission Theory, sup- 

 posed light to be made of minute particles darting out from 

 the sun and every light-giving body. Huyghens, on the con- 

 trary, taught that light is produced by the vibrations or 

 waves of an invisible 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 Philosophy at the 

 Royal Institution 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 t>rder to be able to satisfy the 

 College of Physicians, and practised as a medical man in 

 London, where, in 1801, 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 very famous as one of the first men who deciphered the 

 Egyptian hieroglyphical writings, and you will often hear 



