208 Transactions of the American Institute. 



interior, which consists of unburned gases. Then there is an envelope 

 of luminous gas outside of that, and an exterior mantle almost 

 invisible. 



Even in burning a candle we are burning gas ; for the heat of the 

 flame converts the spermaceti, the parafiine or the wax into gas 

 before it is burned. The combustion takes place partly in the outer 

 cone, and partly in the intermediate or luminous cone ; but in the 

 interior, where the air does not penetrate, there is no combustion. 



The hydrogen burns before the carbon, and the particles of carbon, 

 thus set free, and rendered luminous by the heat, are the cause 

 of the light. What we call soot is eimply a deposit of these carbon 

 particles on a cold surface. 



The form of the flame is due to the ascending current of heated 

 air. It is the ascending current which carries the flame up. The 

 color of the flame depends partly on the temperature, but chiefly on 

 the substances evolved. Different gases produce different colors. 

 Lithium produces a beautiful crimson, and sodium a yellow flame. 



Luminosity of Flames. 



The brightness depends partly upon the degree of heat and partly 

 upon the presence of solid particles which are rendered incandescent. 

 Flames which contain no solid particles emit very little light. The 

 flame of hydrogen and oxygen burning together is very slightly 

 luminous, although it has an extremely high temperature. ■ > Alcohol 

 contains a large amount of hydrogen, but no carbon particles are set 

 free ; hence it is feebly luminous ; its flame is blue. Oils which are 

 rich in carbon give us a luminous flame. 



Hydrogen produces a pale flame. I have here a flame of hydrogen. 

 You see but little light, although the flame is hotter than that of a 

 candle ; but by introducing into the flame particles of carbon it becomes 

 luminous. This apparatus is called a carburettor, being designed to 

 add carbon to the flame. The gas is passed through benzole, which 

 is a volatile fluid rich in carbon ; it takes up a certain quantity of 

 benzole vapor which renders the flame more luminous. This appara- 

 tus is intended for use with street gas, the luminosity of which 

 is increased forty per cent by the consumption of a moderate quantity 

 of benzole. 



Bright flames are produced by bodies which either produce a very 

 high temperature or a separation of solid particles, or both. I pro- 

 pose to introduce in this globe of oxygen gas some fragments of magne- 

 sium. Now. magnesium produces, by its combination with oxygen, 



