398 NINETEENTH CENTURY. W. III., 



pound substance in a fluid state, and so overcoming the 

 force which holds the different elements together and 

 setting them free. This method, called electrolysis, was dis- 

 covered by Davy in 1806, and afterwards thoroughly worked 

 out by Faraday. 



Fourthly, there is the method of spectrum analysis 

 suggested by Herschel in 1822, which was carried dn with 

 great success by Bunsen and Kirchhoff. In this method 

 the substance is turned into gas either by ordinary heat or 

 by the electric spark, and is then examined by the spectro- 

 scope ; the elements being determined by the position of 

 the bright lines they throw on the spectrum. 



There is still a fifth method, about which we have said 

 nothing as yet, and which was chiefly brought into use by 

 the chemist Berzelius, namely the fusing of substances by 

 means of the blowpipe. This instrument is merely a little 

 tube with a mouthpiece at one end and a very minute hole 

 at the -other. By placing the minute hole in the middle 

 of a flame and blowing through the mouthpiece, the centre 

 of the flame is made to burn furiously, and many sub- 

 stances can be melted and decomposed by it which do not 

 yield to ordinary heat. 



By these different methods a very large number of sub- 

 stances have been analysed since the time of Davy and 

 Faraday, and seventy elements or simple substances have 

 been discovered. It is possible that some of these may 

 even at some future time be decomposed and shown to be 

 made up of two elements ; we can only affirm that now they 

 appear to us to be simple substances. Some of these 

 elements have been brought together and made to unite 

 into compound substances by artificial means; as when, 

 for instance, oxygen and hydrogen mixed and lighted by 

 a spark rush together and form water, or when hydrogen 



