I90 GREAT MEN OF SCIENCE 



seventy years later by the investigations of Hittorf, They 

 studied thoroughly and persistently, in well-designed ex- 

 periments, the action of the current on a very large number 

 of substances, particularly with the object of discovering 

 whether they could be decomposed or not. 



Here Davy, an investigator possessed of the liveliest mind 

 and gifted with the surest insight into the secrets of nature, 

 made a wonderful discovery (1807). He separated the alkali 

 metals potassium and sodium, the existence of which, though 

 they had never been seen, had already been suspected for 

 twenty years as constitutents of the well-known caustic 

 alkalis. He found them to have very strange and unheard-of 

 properties. He did not succeed in separating them from 

 solutions of the alkalis; only the water was decomposed. He 

 then melted the solid alkalis, free from water, over a blow- 

 pipe, and passed the current through the molten substance. 

 The negative wire then showed curious flame effects, the 

 origin of which could not be satisfactorily followed; but 

 when he connected the ends of a voltaic battery of many 

 plates, which he had specially constructed for these re- 

 searches, with a piece of moistened caustic potash, which was 

 melted by the current, he saw brilliant globules with a per- 

 fect metallic lustre appear on the negative wire; they were the 

 new metal which he was seeking. When immersed in water, 

 they took fire and burnt instantaneously, swimming about 

 on the surface, and caustic potash was again formed. The 

 remarkable nature of the discovery lay not only in the highly 

 unusual properties of the metal discovered, in the knowledge 

 of an entirely new kind of matter; it was now clear that the 

 other and still undecomposed alkalis and earths must also be 

 oxygen compounds of unknown metals. Thereupon, Davy 

 himself soon actually separated sodium, calcium, strontium, 

 barium, magnesium, in the metallic state, and these bodies 

 themselves soon served as further important aids to chemical 

 investigation. 



