i88o.] 
The Phenomena of Fluorescence. 
625 
III. THE PHENOMENA OF FLUORESCENCE. 
By Edward Rattenbury Hodges. 
OW and then it happens that Dame Nature “ lets the 
cat out of the bag,” or, to speak more philosophic- 
ally, she reveals some hitherto unnoticed and 
unknown fadt or phenomenon which takes us by surprise. 
The exhibition of this to the young or old, the learned or 
unlettered, is invariably followed by the ejaculation — How 
beautiful ! how wonderful ! No matter how diversified our 
habits, gifts, or tastes, we feel a common interest in the 
thing, and mutually share the sentiment of pleasurable 
surprise. We think it may fairly be said that the move- 
ment of a comet through space, or the motions of a 
creosote-drop upon a water surface, are alike equally worthy 
of our attention and our thought ; for He who made the 
glowing gases of the one also formed the oily particles of 
the other, and fully intends us to augment our knowledge 
and exercise our reasoning faculty as much by a careful 
contemplation of these as of other phenomena. By this 
delightful mental exercise we insensibly learn to observe 
and refledt at one and the same time, in consequence of 
being brought into diredt contadt with what a great leader 
in Science has aptly termed “objedtive realities.” From an 
abstradt point of view there is a curious correlation to be 
found in the examples just given. The astronomer makes 
his calculations upon the vast elliptical orbit of the former, 
while the physicist makes mathematics explain the fitful 
gyrations of the latter. And we might pursue the analogy 
still further were it necessary. 
While candidly admitting that much is being done .to 
popularise the fadts of physical science, it is surely justifi- 
able to ask that the rationale of many of its dodtrines should 
also be made sufficiently simple as to find ready access to 
minds of ordinary capacity. To take any material objedt 
and detail its various known properties in plain language is 
by no means difficult ; but to describe the various known 
laws which govern its charadter is, on the other hand, not 
an easy task, for at this point we travel out of the region of 
the material into that of the immaterial. In other words, 
we move away from the domain of the concrete, and enter 
the kingdom of the abstradt. 
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