72 SCIENCE PRIMERS. [MATEIUAL 



liquefied. Each of these gases, according to our 

 hypothesis, consists of particles, and since these can 

 by no known means be further broken up, they are 

 considered to be atoms like those of mercury. 



Nine parts by weight of pure water always yield 

 eight of oxygen and one of hydrogen. The hypo- 

 thetical particle, or molecule of water, therefore, 

 must be composed of atoms of oxygen and hydrogen 

 having this relative weight ; and chemists have grounds 

 for believing that one atom of oxygen and two 

 atoms of hydrogen exist in each molecule of water. 

 If this be so, the structure of water must be more 

 complicated than we thought at first; and each 

 particle of water (the molecule) must be a system 

 composed of three separate atoms. 



50. Elementary Bodies are neither de- 

 stroyed nor is their Quantity increased in 

 Nature. 



It has been seen that when a cubic inch ot water 

 is dissipated by heat, it is not destroyed, but that it 

 merely changes its form from the fluid to the gaseous 

 state, while its weight remains unaltered. If the same 

 cubic inch of water is decomposed into oxygen and 

 hydrogen gases, the water is indeed destroyed, but 

 the matter of which it consisted remains unchanged 

 in weight. If the water weighed 252-5 grains, the 

 oxygen gas will weigh 224-45 grains, and the hydrogen 

 gas will weigh 28-05 grains. And nothing that man 

 has been able to do has affected the weight of a 

 given quantity of either of these gases. So far as we 

 know, elementary bodies retain their weight under all 



