may be fitly denominated the most beautiful and diversified of the Physico-Mathematical sciences. To aid the progress of this study, the following work has been written; and the author, hoping to assist those who, like himself, are climbing the hill of science, has prepared, as a companion to this, a series of introductory papers on the pure sciences and Astronomy, which Treatises will shortly be published. To urge the necessity of Mathametical learning is unnecessary; for as the moon increases or wanes according to her position with the glorious luminary, so science waxes or decays as she is united to, or forced from the Mathematics. When these are combined, the hand of science is, indeed, mighty, and truly the Philosopher is greatly honoured. He combats nature with her own weapons, and to the honour and glory of England let it be remembered, that after nearly six thousand years, in which mankind had been struggling to obtain the superiority over nature; in which Archimedes, and the most illustrious ancients had joined, inventing screws, wheels, and springs; an Englishman vanquished her with a vapour. With regard to the opinions maintained in this work, concerning the nature of light, it is only necessary to say, that although in some degree novel, they have not been embraced without investigation. Persevering study and frequent experiments have been resorted to by the author, yet he has constantly avoided introducing his theory when unnecessary for the explanation of phenomena. I cannot, however, commit this work to the public without returning my acknowledgments to those gentlemen who have assisted me, by their advice and by other means, in the arduous task. Nor shall I ever forget the condescension of my Royal Patron, who has so graciously forwarded my purposes, by his encouraging patronage. The names too of Brougham, Capell, Pond, and others, who have excited my early researches by their effective support, will ever be held sacred in my memory, and the remembrance of the past will constantly urge me to pursue with unremitting energy the work I have undertaken. CHAP. III.—On the Production of Light by various substances . 19 CHAP. IV. On the Influence of Light upon Vegetables,—its CHAP. IV. The appearances under which bodies are observed when their images are seen after reflection from plane, convex, concave, and cylindrical mirrors.. CHAP. V. - History of several discoveries relative to the Reflec- CHAP. III.-On finding the foci of Rays, refracted by passing out of one medium into another of different density. 73 CHAP. IV. On the appearance under which objects are seen when their images are viewed after Refraction, 80 |