Sir William Bragg 43 



A startling discovery made through these X-ray 

 methods is that of the exact size of the carbon atoms in 

 the diamond. (Every boy knows that the hardest of 

 precious stones is made of the same material as charcoal 

 or graphite.) It has been found that the atoms of carbon 

 in the diamond are each 1*54 hundred-millionths of 

 a centimetre in diameter. Each carbon atom in the 

 diamond is at the centre of gravity of four others. These 

 four lie at the corners of a four-cornered pyramid, and 

 the first carbon atom is at the same distance from 

 each of the others. In this simplicity and regularity of 

 structure we have the secret of the intense hardness of the 

 diamond. 



Carbon atoms generally arrange themselves in long 

 chains which are the skeleton structure of fats and oils, 

 or else in rings each containing six atoms. In graphite 

 (blacklead) these rings lie in flakes which slip over one 

 another very easily. That is why a lead pencil writes so 

 easily and why graphite is such a good lubricant. 



Carbon atoms are the basis of dyes, explosives, and 

 many drugs, as well as of foods and fuels, and of our own 

 bodies. X-ray photography is of the greatest value in 

 the investigation of substances such as naphthaline and 

 anthracene, which are of the first importance in the dye 

 industry. 



It is Sir William Bragg's opinion that we may one day 

 be able to go far beyond our present level of investigation 

 and that by the development of X-rays we may be able 

 to see many thousand times farther than we can see 

 to-day. But this goal will not be attained without hard 

 work. In the Royal Institution, where Sir William kindly 

 gave an interview to the author of this chapter, the work 

 goes on steadily, special apparatus having been built for it. 



It was in 1923 that Sir William became Director of the 

 Royal Institution, the most famous of the learned 

 societies of Great Britain. It corresponds to the Academie 



