176 ESSAYS BIOGRAPHICAL AND CHEMICAL 



current. Conversely, when a compound is resolved into 

 its elements, it is generally necessary to impart energy to 

 it ; and the element may, therefore, be said to ' contain ' 

 more energy than its compounds. Now, as Ostwald has 

 pointed out in his 'Faraday' lecture, the progress of 

 discovery has kept pace with the amount of energy with 

 which it was possible at the time to load a compound; 

 and he cited the discovery of the metals of the alkalies, 

 sodium and potassium, by Davy. It was because Davy 

 had at his disposal the powerful battery of the Royal 

 Institution, that he was able to convey enough energy 

 into caustic potash to isolate from it potassium, hydrogen, 

 and oxygen. If we assume that radium, as may be 

 possible, is produced by a spontaneous change in uranium ; 

 and if we also assume that radium contains more energy 

 than uranium ; then as such a spontaneous change must 

 be accompanied, on the whole, by a loss of energy, there 

 must be formed other bodies from the uranium which 

 contain less energy than it does. Such a substance may 

 be iron, which is generally found in company with uranium. 

 If we could concentrate energy into iron, it might be 

 possible to convert it into uranium. 



But there is another side to this question. The nature 

 of the energy required appears to be electric in character. 

 Now it is almost certain that negative electricity is a 

 particular form of matter; and positive electricity is 

 matter deprived of negative electricity that is, minus this 

 electric matter. The addition of matter in any form would, 

 according to all experience, increase mass ; it would also in- 

 crease weight. It is, therefore, conceivable that an element 

 may consist of a compound of two or more elements of 

 lower atomic weight, plus a certain quantity of negative 

 electricity. This might account for the approximate 

 numerical relations which subsist between the atomic 

 weights of the nearly related elements ; and also for the fact 



