HUMPHREY DAVY 191 



Davy already made a thorough study of their properties in 

 the course of many careful experiments, as far as the means 

 available at the time allowed. It happened, as may so often 

 be observed in the history of science and technology, that the 

 proof of the presence and properties of newly recognised 

 things was sufficient to result very soon in their production 

 on almost any desired scale. A goal, the nature and direc- 

 tion of which can already be seen, is soon attainable in other 

 ways - it no longer needs a voyage of discovery to reach it, 

 but merely a journey. Davy's discoveries thus immediately 

 led to fresh exertions to separate the new metals, if possible, 

 also by purely chemical means, which were found in the case 

 of sodium within a year; by reduction at high temperatures 

 with carbon and iron it was soon produced on a large 

 scale. 



In other respects also, Davy's scientific activity was always 

 directed with the highest and most penetrating clarity to- 

 wards the discovery of fundamental facts. When he first 

 produced the phenomenon of the electric arc between two 

 carbon rods by means of his large voltaic battery, the great 

 development of heat became to him of the deepest impor- 

 tance. He recognised that here, just as in Count Rumford's 

 experiment with the cannon, and in his own experiments 

 with friction, the notion, still at that time current, of a pecu- 

 liar heat substance is insufficient as an explanation; for no 

 statement could be made as to the origin of the heat of the 

 electric arc, or of that produced by the heating of wires 

 traversed by an electric current. 



We must also mention much more remarkable investiga- 

 tions made by Davy. We can only refer here to that con- 

 cerning chlorine, the elementary nature of which he was the 

 first to demonstrate, after it had been suspected of containing 

 oxygen. He then also proposed the name chlorine for this 

 element, in place of the term hitherto used 'dephlogisticated 

 spirit of salt' (Scheele's term; which, since hydrogen had 



