102 NATURE AND LIFE. 
among the earliest civilized nations, and the pathetic terror 
those childlike races suffered when, at evening, they saw. 
the crimson globe, that was the source for them of all power 
and all splendor, slowly disappear in the horizon. That 
pious idolatry, far from being a mere utterance of gratitude 
for the wealth of fertility scattered by the sun over earth, 
was a homage, too, to the comforting source of brightness 
and joy, revealing the natural affinity between man and 
light. The Vedas, the Orphic hymns, and cther remains of 
the earliest religions, are full of this feeling, which appears 
again in many poets and philosophers of antiquity, Lucre- 
tius and Pliny among others. Dante, invoking so often 
“the divine and piercing light,” crowns his poem by a 
hymn which more than any thing else is a symbolic descrip- 
tion of the supreme bri&htness. On the other hand, labor- 
ers, gardeners, physicians, unite in bearing witness to the 
beneficial effects-of light. Naturalists and philosophers, 
too, in all ages, impressed with the power of the sun, have 
described its manifold effects. Alexander Humboldt, fol- 
lowing Goethe and Lavoisier, often notices its various in- 
fluences. Yet it was not until the middle of the eighteenth 
century that so rich a subject of study began to attract se- 
rious experimental research; and such are the difficulties 
of this grand and complex problem, that its solution is only 
partly reached, in spite of a long series of attempts. Great 
deficiencies remain to be supplied, and many vaguely-known 
points to be cleared up; nor has an effort even been made 
as yet to systematize all the groups of results gained. The 
latter task we propose to attempt here, with the purpose of 
showing by a remarkable instance the manner of evolving 
knowledge through the power of the experimental method, 
the sequent, cumulative, and mutually-supporting character 
of well-conducted experiments, and their endless wealth of 
instruction; in a word, the process adopted by eminent men 
in the great art of wresting her secrets from living Nature. 
