OO DK. GOODMAN ON LIGHT. HEAT, 



by lightning, and here we have a beautiful illustration of 

 the phenomenon. 



Exp. 13. — A glass tube affixed to a short brass neck by 

 sealing-wax, and bent in the middle to an angle of about 

 22 degrees, was at its other extrenjit}^ fitted to the receiver 

 of an air-pump by a cemented leaden tube. The stem 

 was screwed to the percussion orifice. The apparatus being 

 duly arranged upon a vice for percussion, and the tube ex- 

 hausted to 28 inches — percussion was now made in a room 

 dimly lighted by one small candle. The ordinary radiating 

 Jiame was seen issuing from the orifice into the exhausted tube. 

 This flame was considerably inferior in intensity and brilliancy 

 to the ordinary flame developed in atmospheric air, although 

 probably of similar dimensions. 



This experiment proves that the normal light and heat 

 of the potassium flame is not derivable from the atmosphere, 

 or combustion, and exists independently of them. 



Exp. 14. — The experiment was repeated several times 

 with similar results, the flame extending beyond the elbow 

 or bent portion of the tube, but at all times accompanied 

 with considerably diminished lustre, even in the dark. The 

 flame within the tube being retained within certain limits, 

 resembled that which emanates from a blow-pipe of low 

 power ; but the fire which issued from the percussion orifice 

 in open air was at all times like that proceeding from the 

 mouth of a pistol, rocket, or other species of fire-work — in 

 diverging lines or radii — and exhibiting the evident repulsion 

 of their individual particles. 



Exp. 15. — On applying a bent copper tube, of about 2 

 inches in length, to the percussion orifice, no flame could 

 be seen on percussion, probably on account of the conduct- 

 ing and consequently cooling nature of the tube. In one 

 instance, however, large globules of red-hot metal fell from 

 the mouth of the tube. 



