CHEMISTRY. 161 



its atom is assumed as unity, and is the standard of 

 comparison for the relative weight of the atom of all 

 other bodies. 



The only compound of hydrogen and oxygen that 

 we are acquainted with is water, in which the oxygen 

 is to the hydrogen as 7 to 1. The number 7 is, 

 therefore, assumed as the relative weight of the atom 

 of oxygen; and water is a binary compound, con- 

 taining an atom of hydrogen with an atom of oxygen 

 in every atom of water. 



Chemical Signs. 



O Represents an atom of oxygen. 

 .... ditto of hydrogen. 

 .... ditto of azote. 

 @ . . . . ditto of carbon. 



Atomic Theory. 



The atomic theory in chemistry supposes that the 

 atoms of bodies unite together; that the atom of 

 each body has a determinate weight, and that this 

 weight regulates the proportion in which bodies com- 

 bine with each other. 



Atoms, 



It is the general opinion, that the elements of bo- 

 dies consist of atoms or extremely minute particles 

 incapable of further division. It is impossible to 

 demonstrate the truth of this opinion, but it has 

 been almost universally admitted since the time of 

 Bacon. 



According to the theory of Boscovick, the first 

 elements of atoms of matter are indivisible, unex- 

 tended, simple, homogeneous, and finite in number. 

 Their actual contact is impossible. 



Ultimate Atoms. 

 Dr. Wollaston came to the conclusion, that the 



