C 449 3 
XX. An Inquiry concerning the chemical Properties that have 
been attributed to Light. By Benjamin Count of Rumford, 
F. R. S. M. R. I. A . 
Read June 14, 1798. 
In the Second Part of my Seventh Essay, (on the propagation 
of heat in fluids,) I have mentioned the reasons which had in- 
duced me to doubt of the existence of those chemical properties 
in light that have been attributed to it, and to conclude, that all 
those visible changes produced in bodies by exposure to the ac- 
tion of the sun's rays, are effected, not by any chemical combi- 
nation of the matter of light with such bodies, but merely by 
the heat which is generated, or excited, by the light that is ab- 
sorbed by them. 
As the decision of this question is a matter of great impor- 
tance to the advancement of science, and particularly to che- 
mistry, and as the subject is in many respects curious and 
interesting, it has often employed my thoughts in my leisure 
hours ; and I have spent much time in endeavouring to con- 
trive experiments, from the unequivocal results of which the 
truth might be made to appear. Though I have not been so 
successful in these investigations as I could wish, yet I cannot 
help flattering myself, that an account of the results of some 
of my late experiments will be thought sufficiently interesting 
to merit the attention of the Royal Society. 
MDccxcym. 3 M 
