COMBUSTION. 131 



CHAPTER X. 



COMBUSTION. 



167. Importance of the Subject The interest attending 

 the subject of combustion is very great, because the chem- 

 ical processes involved in it produce such varied and ex- 

 tensive effects in the world. We are dependent upon com- 

 bustion in many ways for our comfort and enjoyment, and 

 even for the continuance of life. The preparation of our 

 food is effected in part by combustion. We guard by it 

 against the influence of cold. Nay more, it is by a real 

 combustion, though without flame, that the heat of our bod- 

 ies is maintained, as we shall show you in a part of this 

 chapter. Combustion gives us our light in the darkness 

 of night. It is very busy in many of the arts, especially in 

 preparing the metals for the various uses to which we ap- 

 propriate them. In these latter days it has been put ex- 

 tensively to a new use, in propelling steamers on the water, 

 and locomotives on the iron roads that thread the land. It 

 is by combustion, also, that the missiles of war are hurled. 

 The grandest scenes of destruction witnessed in the earth 

 come from combustion conflagrations of towns and cities, 

 and forests and prairies ; explosions of masses of combusti- 

 ble material, and, above all, the bursting forth of the im- 

 mense and lofty volcanoes. Combustion, then, is one of the 

 principal things with which man has to do, and therefore a 

 thorough knowledge of it is not only interesting, but of 

 practical importance. As the old proverb has it, fire is a 

 good servant, but a bad master; and we trust that you will 



