178 J. MORISON : ADDRESS 



next, when this increase becomes considerable, at a temperature 

 which varies in different substances, the molecules begin to 

 move more rapidly, and to leave their own special spheres, and 

 move freely amongst each other. Then the solid becomes a 

 liqviid. Still continuing to apply heat, the separation of the 

 molecules becomes much more considerable, the rate and extent 

 of their motion much greater, and they are continually jostling 

 against each other. In other words, the liquid is converted into 

 a gas. The motion of the molecules in gases is exceedingly 

 rapid. Clavering has calculated that the molecules of air move 

 at the rate of 485 miles a second, and that the rate of motion of 

 hydrogen molecides is no less than 1,844 miles a second. The 

 molecules are continually striking against each other and against 

 the sides of any vessel which may contain the gas. It has been 

 calculated that a molecule of air ixnder ordinary atmospheric 

 pressure and at a temperature of 32° F. strikes another molecule 

 no less than 4,700 million times a second. 



Not only are the molecules constantly in motion, but the 

 atoms which compose them are continually vibrating to and fro 

 with extreme rapidity, and this vibration becomes more and 

 more rapid as the temperatm-e increases. Sometimes with the 

 application of heat, the atomic motion becomes so greatly 

 increased that the equilibrium of the molecules is destroyed, and 

 the atom from one kind of molecule passes into the sphere of 

 another kind of molecule, but what is known as chemical action 

 comes into operation, new combinations of atoms or new molecules 

 are formed, and new chemical compounds are the result. Thus, if 

 in the presence of air we apply a light to a jet of coal-gas, which 

 is mainly composed of carbon and hydrogen, the molecules of the 

 gas in contact with the light are heated, become unstable, and 

 undergo dissolution. The same thing occurs to the heated 

 molecules of oxygen in the ai;*. Then the free atoms of oxygen, 

 carbon, and hydrogen mix with each other and enter into new 

 combinations, forming molecules of carbon dioxide and water. 



Thus we find that matter is composed and built up of exceed- 

 ingly small particles called molecules, differing in character in 

 different substances ; that molecules are made up of one, two, or 

 more minute bodies called atoms, which also differ in character in 

 the various elementai'y bodies ; that the molecules of compounds 

 are composed of atoms of two or more different kinds ; that both 

 molecules and atoms are immersed in and separated by a 

 perfectly homogeneous fluid known as the ether ; and that both 

 atoms and molecules are continually moving to and fro with 



