SOME CONSEQUENCES OF GRAHAM'S WORK 595 



blance to the metal lead. The black forms of carbon are easily 

 oxidised by wet oxidising agents. All the forms of carbon, 

 probably, are of highly complex molecular structure and 

 differently constituted. But the chemist forms his opinion of 

 carbon from the study of its compounds generally : the abstract 

 conceptions which are associated with the term carbon in his 

 mind have nothing in common with what is known of any of 

 the forms of carbon, such as the diamond, graphite or charcoal. 

 It is on this account that the study of chemistry is so difficult— 

 because it is impossible to attach quantitative significance to so 

 many of the chemist's conceptions. 



The outlook has been changed entirely within the last few 

 years by the discovery of radium ; as the President of the British 

 Association said last year at Portsmouth : " It has widened the 

 bonds of thought." The discovery has put us in possession of 

 a substance whose properties are without precedent. Radium 

 is accounted an element, because it forms salts more or less like 

 those of barium. But when left to itself (as salt) it breaks up 

 spontaneously into helium and a condensible emanation, which 

 itself is unstable and rapidly gives rise, it is asserted, to a series 

 of products each less stable than itself, helium being a product of 

 the decomposition at nearly every stage. It is suggested that it 

 ultimately yields lead. But radium itself is now supposed to be 

 derived from uranium, a substance regarded as an element 

 before the discovery of radium ; and the passage from uranium 

 to radium is said to involve the separation of three molecules 

 of helium from the former. 



The evidence on which some of these conclusions is based 

 is of a very special and daring character and by no means 

 universally accepted as sufficient at present : but in such a case, 

 at first, to meet the emergency, it is almost necessary to throw 

 caution to the winds. 



A relatively enormous amount of energy is given out from 

 radium as the change proceeds and the helium molecules are 

 expelled with extraordinary velocity ; apparently, however, the 

 change takes place independently of all external influences and 

 cannot be hastened or retarded by any known means. It is 

 in this respect particularly that the behaviour of radium is so 

 marvellous. 



Professor Turner in his address to the Mathematical and 

 Physical Section of the British Association at Portsmouth last 



