Cold Air in maintaining Heat. 447 



knowing what I have seen and done in regard to the heating 

 effects of currents of cold air on iron ; and consequently I beg 

 permission to acquaint you with the particulars ; and if you 

 think they are of sufficient interest to occupy a place in the 

 forthcoming Number of the Philosophical Magazine, perhaps 

 T ou will oblige me by forwarding the same for publication. 



I was at Sheffield in last December, and then a Mr. Linley, 

 jellows-maker of that town, showed me the following curious 

 xperiments : first, a rod of iron, about an inch in diameter, 

 vas heated at one end in a forge fire, up to a full white heat, 

 -hen quickly withdrawn from the fire and exposed to a strong 

 blast of cold air from a forge bellows ; the iron immediately be- 

 came so hot as to fuse, and the liquefied matter was blown off 

 and burnt in the air with the scintillating appearance of iron 

 wire burning in oxygen gas; and so continued to melt until a 

 pound or more of the metal had been thus wasted. 



Another mode of producing the same action consisted in 

 heating a rod of iron, as before; but instead of a blast of air, 

 it was tied to a cord, and by it whirled round in a vertical 

 plane; thus by passing swiftly through the cold air it melted, 

 and was thrown off in beautiful scintillations, appearing as 

 luminous tangents to the circle in which the bar was moved. 



I have since applied a heated bar of iron to the periphery 

 of a revolving wheel, and by an including tin hoop or guard, 

 it is thus made an interesting class experiment. 



The cause of this augmentation of temperature is, I con- 

 ceive, referable to the oxidation of the metal, which takes 

 place freely under the conditions of the experiments here re- 

 corded. Then, as is well known, the formation of the oxide 

 is accompanied with a great development of heat; and the 

 cases before us are striking examples of the heating influence 

 by chemical action predominating over the cooling effect of 

 the air conjoined with the radiating force. 



The success of these experiments chiefly depends upon 

 having the iron at first of a sufficiently high temperature, and 

 upon the velocity of the air from the bellows, or otherwise the 

 velocity of the iron through the air. For the iron at a white 

 heat is greedy of oxygen, which the air solidifies. Then the 

 oxide thus formed requires to be blown or whirled off, in order 

 that fresh surfaces of the metal may be exposed to the air. 



When the blast is employed, we see the oxide fusing, and 

 deep channels scooped out in the bar by the rushing air on 

 that side where the current is directed. 



I am, dear Sir, yours truly, 



Robert Addams. 



Kensington, Oct. 16th, 1837. 



