
ADDRESS. xlvii 
media exhibiting “fluorescence” was found to be very large, consisting chiefly 
of organic substances, but comprehending, though more rarely, some mineral 
bodies. The direct application of the fact, as we now understand it, to many 
highly interesting and important purposes, is obvious almost on the first an- 
nouncement. The facility with which the highly refrangible invisible rays of 
the spectrum may be rendered visible by being passed through a solution of 
sulphate of quinine or other sensitive medium, affords peculiar advantages 
for the study of those rays; the fixed lines of the invisible part of the solar 
spectrum may now be exhibited to our view at pleasure. The constancy 
with which a particular mode of changing the refrangibility of light attaches 
to a particular substance, exhibiting itself independently of the admixture 
of other substances, supplies a new method of analysis for organic compounds 
which may prove valuable in organic chemistry. These and other applica. 
tions of the facts as they are now explained to us, will probably form subjects 
of notice in the Chemical and Physical Sections, and a still higher interest 
may be expected from the discussion of the principle itself, and of the founda- 
tion on which it rests. A discovery of this nature cannot be otherwise than 
extremely fertile in consequences, whether of direct application, or by giving 
rise to suggestions branching out mure and more widely, and leading to 
trains of thought and experiment which may confer additional value on the 
original discovery, by rendering it but the first step in a still more extensive 
generalization. 
As the interest of this discovery is not confined to a single branch of 
science, the Officers, with the approbation of the Local Committee, have 
requested Mr. Stokes to favour the Association with an exposition of the 
subject at an evening meeting, when the members of the different sections 
may be able to attend without prejudice to their respective sectional duties : 
and in that view I have thought that this brief introductory notice might not 
be misplaced, a notice which I cannot conclude without adverting to the 
gratification which all who cultivate science in this part of the United 
_ Kingdom must feel at the rising eminence of their highly accomplished 
fellow-countryman. 
Among the subjects of chemical inquiry which may well deserve the 
attention of a combination of philosophers, perhaps few could more usefully 
occupy their joint labours than the revision of the Equivalent Numbers of the 
Elementary Bodies. This is a task which must necessarily require the co- 
operation of several properly qualified individuals, if it be accomplished 
within anything like a reasonable period of time. Most of the Numbers now 
in use depend upon experiments performed by Berzelius, at a time when the 
methods of research then known were inadequate, even in such hands, to 
determine these constants with an accuracy sufficient for the wants of science 
at the present day. So much has this been felt to be the case, that many 
of the most accomplished chemists now living have undertaken extensive 
and laborious, though isolated researches, upon the combining quantities of 
d2 
