STEAM BOILER EXPLOSIONS. 47 



I hat water kept in a room tends to keep the air pure ; not 

 itiically, but by its natural or chemical action with the 

 atmospht : 



Again, if we lay aside, a loaf of bread it will be chemically 

 r.hangi'd iu a few days, and become hard and stale, instead of 

 soft and moist. Scientific works tell us that there is moisture 

 in the air, but all experience proves to us rather that there is 

 none, fr we can keep nothing with moisture in it for any length 

 of time. Our bread becomes stale, our wood loses its sap, our 

 gardens thirst for rain, and even our tumbler of water eventually 

 rates into air, in the atmosphere. 



There is no more latent moisture in the air, than there ia 

 latent dryness in the sea ; and We would just as soon expect a 

 piece of new bread to remain moist, on a warm summer's day, 

 as a piece of stale bread to remain dry when immersed in water. 



But there is no need for enumerating further examples, for 

 every natural change or action is chemical action, and is caused 

 by the reciprocal attraction and repulsion of the two classes of 

 atoms. 



It may not be out of place to record here, an example of 

 chemical action, which is causing the destruction of life and 

 property almost every day. We refer to 



STEAM BOILER EXPLOSIONS. 



No clue seems as yet to have been found elucidating the catlse 

 of explosion. Boilers which have been tested by an hydraulic 

 pressure of 100 Ibs. to the square inch have exploded at a pres- 

 sure of 30 Ibs. and although it has been surmised that this 

 could not have been caused by pressure, and that some other 



