364 NINETEENTH CENTURY. FT. in. 



lamp, which has saved so many lives, and for the invention 

 of which he received the title of baronet. It was here also 

 that he made his first experiments in electro-chemistry, which 

 is the only one of his many discoveries of which we can speak. 



Discovery of Electrolysis, or the Decomposition of 

 Water by an Electric Current, 1800-1806- In the year 

 1800, two men named Nicholson and Carlisle discovered by 

 chance that when the two wires of a voltaic battery were 

 dipped in water, bubbles of gas rose up from them. They 

 also found by experiment that the gas from one wire was 

 oxygen, and from the other hydrogen; but where these gases 

 came from, whether they were produced by the electricity, or 

 came from the battery, or from the water, they could not 

 tell. Moreover, besides the oxygen and hydrogen which 

 came off, there also appeared an acid of some kind at the 

 positive pole, as was shown by damp litmus paper turning 

 red (see p. 229), and an alkali appeared at the negative pole 

 which turned this red litmus paper blue again. This looked 

 as if the electric current had produced something in the 

 water, for Cavendish, as you will remember, had shown 

 that pure water is made of oxygen and hydrogen only (see 

 p. 231). Many chemists, therefore, set themselves to try 

 to discover what effect the electric current had on the 

 water, and Davy in 1806 succeeded in solving the question. 



The history of his^ experiments is especially interesting 

 because it shows, as we have noticed so often before, that a 

 patient and careful inquiry into nature always gains a true 

 answer in the end. Davy did not believe that the electric 

 current produced anything in the water ; he thought that 

 both the acid and the alkali came from the vessels that were 

 used. So he set to work steadily to clear away all possibility 

 of impurities. He took distilled water, and used cups first 



