$4 tf&a oniGitf of 



is not in a condition to do so. Light is caused only when thb 

 ntoms are in excessive motion^ when the poles are disturbed and 

 clash with each other / and they are only in this condition when 

 the atoms are unequally divided, 



In calm water, the different classes are thoroughly at rest, and 

 arranged in natural atomic position, but the crest of a waV6 

 in falling, or a steamer in motion, presses the atoms into 

 collision with each other, many consequently combine, while 

 instant commotion en&ues throughout the mass, the greater 

 lights attracting the lesser ; till by rapid attraction and repul- 

 sion, the atoms are in order again, and darkness reigns supreme* 



It may be asked why these little globes of light, having once 

 been set in motion, do not continue to attract the light 

 producing atoms, till they form an immense ball of fire t 

 Because crystallization, or the aggregation of any particular class 

 of atoms, can only ensue when such atoms preponderate over 

 others, and as the light atoms in the water, are few, in com- 

 parison to the mass of other atoms in solution, therefore, as 

 before, the lesser must necessarily give way to the greater. 



The streak of light left by a fish as it dashes through the 

 water, or a meteor in passing through the atmosphere, is 

 evolved on the same principle. (See chapter on Auroras.) 



In the fire-fly, the light is caused by the atomic mingling of 

 two different kinds of suitable material, one of which the fly 

 manufactures and developes in its body from its food ; the other 

 is probably derived from the atmosphere. The heat from this 

 light is very slight) no greater than the temperature of its insect 

 body. 



Many healthy persons after a brisk walk will ignite our 1 

 ordinary coal gas, by merely applying their finger to the jets 



