Scientific Lectures. 199 



SCIENTIFIC LECTURE -V. 



ON COMBUSTION. 



By Prof. C. F. Chandler, of Columbia College ; January 5th, 1872. 



(Reported Stenographically.) 



Ladies and Gentlemen. — When a solid substance, capable of 

 enduring heat without decomposition, is subjected to a high tempera- 

 ture, it emits light. A piece of platinum or porcelain, at a certain 

 temperature, becomes red hot ; it emits red light. If we raise the 

 temperature until it becomes more intense, the light becomes whiter ; 

 and, at a still higher temperature, a violet tint appears. Thus the 

 application of heat develops, first red, then white, and finally violet- 

 light. The lower temperature is illustrated by red-hot iron, and the 

 higher by the Drummond light, which is simply lime raised to the 

 temperature which produces the violet heat. 



Bodies in this condition are said to be incandescent. If we with- 

 draw the source of heat, the body ceases to be luminous, passing from 

 the violet to the white, then to the red, and finally ceasing to emit 

 light. If we examine the body after it is cooled, we find that it has 

 undergone no change. This is simply ignition. A body is ignited 

 when it is heated to such a degree as to emit light. 



If, instead of lime, we subject charcoal to a high degree of heat, 

 we find that at a certain temperature the charcoal emits light ; but it 

 continues to emit light after the source of heat is withdrawn, and it 

 wastes away until it finally disappears, leaving a little ash ; if the 

 carbon were entirely pure, it would leave no ash or residue what- 

 ever. This is comJntstion, as distinguished from mere ignition. The 

 charcoal burns, and its temperature is maintained by the heat it 

 evolves by uniting with the oxygen of the atmosphere. 



Combustion is intense chemical action ; and any chemical action, if 

 the temperature is raised sufficiently, may produce the phenomena of 

 combustion. In other words, when the chemical action is accompa- 



