J. W. Draper—Distribution, ete., in the Spectrum. 25 
Art. III.—Researches in Actino-chemisiry. Mnmotr SEconp. 
On the Distribution of Chemical Force in the Spectrum ; by 
JoHN Witiiam Draper, M.D., LLD., President of the Fac- 
ulties of Science and Medicine in the University of New York. 
Wirn scarcely an exception, the most recent works on the 
chemical action of radiations an seg nate the se et, 
lar changes in any special substance is determined by the absorp- 
tive property of that substance. 
second in a paper in the same journal, 
between the phenomena of the chemical rays and those of 
radiant heat” (Sept., 1841). eee 
he opinion commonly held respecting the distribution a 
‘ } ; 
the higher parts of the spectrum a special principle prevails, to 
which the Soabeeb ee of & actinic aii is often applied—an 
Mappropriate iteration. In these pages I use the derivatives of 
axris, not in this restricted sense, but as expressive of radia- 
Hons of every kind. This is their proper signification. = 
_ Every part of the spectrum, no matter what its refrangibility 
may be, can produce chemical changes, and therefore there is 
No special localization of force in any limited region. Out of a 
large bod of evidence that might be adduced, I select a few 
prominent instances. 
