220 SCIENCE OF COMMON THINGS. 



Construction of furnaces. Combustion. 



1463 In the construction and arrangement of a furnace for warming, 

 what two points are of special importance, so far as regards the economy of 

 fuel? 



1. The perfect combustion of the fuel ; and 



2. The best possible transmission of all the heat 

 formed, into the air that is to pass into the rooms of 

 the house. 



1463 How is the first of these requisites obtained? 



By having a good draught and a fire-box which is 

 broad and shallow, so that the coal shall form a thin 

 stratum ; by which arrangement the carbonic acid gas 

 will be freely formed, and pass off without a previous 

 production of an imperfectly burnt product. 



1464 How is the second of these requisites attained ? 



By providing a great quantity of surface in the form 

 of pipes, drums, or cylinders, through which the smoke 

 and hot gases must pass on their way to the chimney, 

 and to which their heat will be imparted, to be in turn 

 delivered to the cold and pure air of the rooms of the 

 house. 



CIIAPTEE II. 



t 



COMBUSTION. 



1465 What is combustion ? 



Every species of combustion with which we are 

 familiarly acquainted is the rapid chemical union of the 

 oxygen of the air with a combustible body, attended 

 with the evolution of light and heat. 



1466 flow may combustion, as we ordinarily see it, be regarded ? 



It may be regarded as simply & process of oxidation. 



1467* What do we mean by the term oxidation f 



