MAKIXG LAMP-BLACK. 141 



become intensely black if they are interrupted on the way, 

 and suddenly cooled before they find oxygen to combine 

 themselves with. They are, moreover, so inconceivably 

 minute, that when assembled together they form an impal- 

 pable powder, far softer and finer in the minuteness of the 

 division than it would be possible to make masses of car- 

 bon by any artificial process of pulverization. This mode, 

 accordingly, of procuring a black powder for paint, and for 

 painter's work, is practically employed to a great extent. 

 The engraving shows how lamp-black is manufactured on 

 a large scale. 



The fire is made in the little grate at / it is made of 

 pitch, or tar, or some other hydro- 

 carbon containing a large propor- 

 tion of carbon. The substance is 

 heated by a fire below it, and then 

 is set on fire above, and is furnished 

 with a limited supply of oxygen 

 through small holes made for the 

 purpose. In consequence of this lim- 

 ited supply of oxygen, the combus- 

 tion is imperfect, and a large por- 



form of a dense black smoke into the chamber b c, where it 

 attaches itself to the walls, and also to the sides of the 

 cone <?, which is placed there to receive it, and can be 

 raised or lowered at pleasure by the cord and pulley. 

 When a sufficient quantity of the deposit has accumulated, 

 it is removed from the walls and the cone, and packed in 

 papers for transportation and sale. 



This being the philosophy of the light produced by a 

 flame of a lamp that is, by the incandescence of solid 

 parts heated by the combustion and floating up through 

 it it is plain that the way to increase the light is to in- 



