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 other 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 anything else is a symbolic descrip- 

 tion of the supreme brightness. 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. 



