on the Production of Light from Bodies. 31 
of their powder on a plate of iron nearly red hot, I had the sa- 
tisfaction to observe it emitting a considerable light. Extending 
this mode of trial, I found that the phosphorism of almost all 
bodies might be made apparent either by heat or by attrition ; 
I shall therefore divide the subject of this Paper into two parts: 
I. On the light produced by Heat. — II. On the light pro- 
duced by Attrition. 
I. 
The best general method of producing the light by heat is, to 
reduce the body to a moderately fine powder, and to sprinkle it, 
by small portions at a time, on a thick plate of iron, or mass of 
burnt luting made of sand and clay, heated just below visible 
redness, and removed into a perfectly dark place. 
The following is a list of such bodies as I have found to be 
luminous by this treatment, arranged according to the appa- 
rent intensity of their light. 
1. Blue fluor, from Derbyshire, giving out a fetid smell on attri- 
tion. 
2. Black and grey marbles, and fetid white marbles, from Derby- 
shire. 
Common blue fluor, from Derbyshire. 
Red feldspat, from Saxony. 
3. Diamond. 
Oriental ruby. 
Aerated barytes, from Chorley, in Lancashire. 
Common whiting. 
Iceland spar. 
Sea shells. 
Moorstone, from Cornwall. 
