Sir JVilliam Bragg 39 



regarded as particles, had also the properties of waves. 

 Considerably puzzled, he called in his son, William 

 Lawrence Bragg, then little more than twenty years of 

 age, and one result of their researches was that in 1915 

 they were jointly awarded the Nobel Prize for Physics. 

 The story of these interesting experiments is told in 

 Sir William Bragg's book An Introduction to Crystal 

 Analysis (Bell, 1928). 



The book begins with the account of an experiment 

 made by M. Laue in the year 1912, which proved that 

 X-rays were of the same nature as rays of light. M. Laue 

 passed a fine pencil of X-rays through a crystal of the 

 precious stone called beryl and allowed it to fall on a 

 photographic plate. After an exposure the plate was 

 developed, and the result was a most exquisite pattern 

 resembling a great flower. 



The experiment was a complete success, and gave 

 convincing proof that X-rays are of the same nature as 

 rays of light ; also it opened out a new field of research, 

 which has proved to be of the greatest practical value to 

 industry. The explanation is that it gave chemists a new 

 method of investigating the structure of solid bodies. 

 Hitherto this kind of examination had been confined to 

 liquids and gases, but with the aid of the X-ray and the 

 camera chemists were at last able to explore solids, and 

 during the past eighteen years these researches have been 

 extended to all kinds of objects, such as wool fibre, silk, 

 metals, wood, rubber, etc. 



As Sir William said in one of his Christmas lectures, we 

 are now able to look ten thousand times deeper into the 

 structure of the matter that makes up our universe than 

 we were able to look when we had to depend on the micro- 

 scope alone. The discoveries of radio-activity and of 

 X-rays have given us new eyes, so that we can understand 

 many things that formerly were obscure. 



The chemistry of any solid body depends upon the 



