26 THE CREATION OF MATTER 



gases. By certain arrangements such a quantity of water 

 may be poured into a glass globe as, when raised to the 

 boiling point and wholly evaporated, will fill the globe. 

 Pour in more water, and not another molecule will at the 

 same temperature and pressure be added. But if ether 

 be substituted, the same number of molecules will rise 

 among the steam. A third and a fourth vapour may be 

 added, and each will be of the same number. The 

 molecules of steam thus prevent any more of their own 

 kind from rising among them from the water than 

 according to temperature and pressure, but they welcome 

 those of ether, or of any other kind. The ether molecules 

 also determine their own number, but they do not stand 

 in the way of other kinds. 



Each gas has its own measure of diffusive force. It is 

 inversely proportional to the square root of its density. 

 A bottle of hydrogen, open to the air, will lose 9 4 '5 per 

 cent, of this gas in the same time as that in which 

 a bottle of carbon dioxide will lose 47 per cent. In 

 different gases the diffusive power is different, but in the 

 same gas it is the same. 



The law is in many respects a very wonderful one. 

 Non-interference of a gas with other kinds of molecules, 

 while resisting the rising or descending among them of 

 additions of their own kind, is a very remarkable arrange- 

 ment. Were it otherwise, life could not be continued. 

 Deleterious gases would collect. Carbon dioxide breathed 

 out by all animals, were it not diffused through the air, 

 would fill rooms and all kinds of enclosures and places 

 where animals congregate, and would be the ending of 

 their life. 



Avogadro's law. Equal volumes of all substances, in 

 the state of a perfect gas, and under like conditions, 

 contain the same number of molecules. A jar of oxygen 



