CH. XXXVI. JOHN DALTON. 371 



By these different methods a very large number of sub- 

 stances have been analysed since the time of Davy and 

 Faraday, and sixty-four 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 

 and chlorine mixed together and placed in the sunlight 

 unite to form hydrochloric acid.^ This method of bringing 

 elements together to form a compound substance is called 

 synthesis^ and is exactly the opposite of analysis, or the 

 splitting up of a compound substance into its elementary 

 parts. 



To follow out the gradual development of synthesis and 

 analysis, and to see how all the different elements and com- 

 pounds were in this way determined, would be to write a 

 work upon chemistry. There is only one other general 

 principle which we ought to try and understand here ; 

 namely, the proportions in which the elements combine to 

 form substances. This principle, which lies at the root of 

 all our modern chemistry, was first worked out by a poor 

 schoolmaster named Dalton. 



Dalton shows that the Different Chemical Elements 

 always Combine in Definite Proportions. — John Dalton 

 was bom of Quaker parents in 1766, near Cockermouth, in 



• Sir H. Davy was the first to discover, in 1807, that hydrochloric 

 acid is made merely of hydrogen and chlorine ; before then it was 

 believed that every acid must have oxygen in it. 



