537 
ARTICLE XXII. 
Memoir on the Constitution of the Solar Spectrum, presented to 
the Academy of Sciences at the Meeting of the 13th of June, 
1842, by M. Epmonp BrecQuEREL. 
[From the Bibliotheque Universelle de Geneve, No. 80, for August 1842.] 
THE faculty of illuminating bodies is not the only one pos- 
sessed by solar light; it has also different properties which are 
manifested to us by the changes which it produces on some of 
these same bodies, such, for example, as raising their temperature, 
of causing chemical modifications to take place among the ele- 
‘ments of some of them, and, lastly, of giving to others the faculty 
of being self-luminous or phosphorescent. These different pro- 
perties, long since known, have given rise to a multitude of 
beautiful investigations by natural philosophers and chemists ; 
but as these are described in works on physics, I shall not enter 
into any detail upon this subject. 
The chemical action of light has long been the object of my 
favourite studies, which have led me to recognise a property 
/ common not only to the spectra formed by the chemical rays, 
_ but also to those which are owing to the phosphorogenic rays. 
This is the motive which has induced me to bring together in a 
single memoir all the observations which I have recently made 
on this subject. 
It is not my intention to enter upon the constitution of the 
luminous spectrum, as the title of the memoir appears to indi- 
cate, but on that of the spectra formed by the radiations which 
accompany solar light and light in general; that is to say, of 
chemical, phosphorogenic and calorific spectra. 
In this memoir, by chemical spectrum will be designated the 
whole of the rays which, in the solar spectrum, impress a sub- 
stance which has the property of being modified under their in- 
fluence ; and by phosphorogenic spectrum, the whole of the rays 
which excite phosphorescence on a sensible substance. 
This memoir will be divided into four parts, as follows: the 
first will comprehend a rapid description of the formation of the 
luminous spectrum and of the discovery of Fraunhofer; the 
