328 Aphlogistic Lamp. 
Art. XIV.— Description of the Aphlogistic Lamp. 
Communicated by Dr, J, L. Comstock, of Hartford, Ct. 
In the construction of this lamp, the object is to keep a 
coil of wire in a state of permanent ignition, without either 
flame or smoke. 
The principle on which it is constructed, I believe was 
first discovered by Sir H. Davy. He found that on heat-_ 
ing the end of a piece of platina wire red hot, and instantly 
holding it near the surface of some ether placed in a wine 
glass, the wire was kept at a red heat as long as the experi- 
ment was continued. Chae 
Whether Sir Humphrey pursued the subject any farther, 
Iam not informed. It is most probable, however, that he 
did not, as it is stated in a London paper of the last year, 
that Prof. Ure of Glasgow had determined the circumstan- 
ces which modify the performance of the lamp, and that one 
constructed by him was in full action in that city, (London,) 
and had excited much public curiosity. 
This. notice contains some directions concerning the size 
of the wire, and the manner of coiling it. { have, however, _ 
seen no description of this lamp, which would enable one 
readily to construct it. The following may therefore inter- 
est such readers as have seen no account of this curious dis- 
covery. 
The principle on which the aphlogistic lamp is con- 
structed involves two conditions, which are absolutely re- 
quisite, viz : that we make use of a combustible substance 
which evaporates at a low temperature, and a metal which is 
a bad conductor of caloric. For the combustible alcohol 
seems best suited to the purpose. Sulphuric ether, aside 
from its high price and disagreeable smell, 1 have found 
sometimes to fail ; the ignition ceasing without any obvious 
eause. In regard to the metal, gold and silver both fail in 
consequence of the rapidity with which they conduct calor- 
ic. Silver too would soon be destroyed by the intense 
heat. 
Iron, although so bad a conductor as to remain ignited 
for a time, soon fails, being converted into red oxide. Pla- 
tina seems to be the only metal adapted to this purpose, 
