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Researches on light in its chemical relations
Researches on light in its chemical relations Author:Robert Hunt Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 36 CHAPTER II. ANALYSIS OF THE SUNBEAM. (40.) It is important on entering on the study of a set of phenomena, which are still among the novelties of sci... more »ence, that we should make ourselves acquainted with all the conditions, which may directly or indirectly influence them. The chemical changes produced by the solar rays have usually been regarded as a function of Light (the luminous principle as distinguished from heat or any other power). It has been stated in the historical chapter (30) that some of the Continental philosophers, and particularly Berard, were disposed to refer the phenomena of chemical change under the influence of radiant action, to some principle which, although associated with Light in the sunbeam, as heat is, was still to be distinguished from Light, by ita being incapable of producing visibility, or colour. The object of this volume being the full examination of this problem, it is proposed to consider the phenomena of the strictly luminous radiations, and of the heat radiations, previously to entering on the investigation of the chemistry of the sunbeam. (41.) If a hole is made in the window-shutter of a darkened room, there will be, if the sun is shining, a bright circular image formed upon the floor, or on a screen placed to receive it. This circular spot of Light is an image of the sun, as we may prove by placing the eye, protected by a smoked glass, in the path of the sunbeam, when that luminary will be distinctly seen through the hole, or, if we receive such an image when the sun is partially eclipsed, it will exhibit only the still luminous portion of the disc. (42.) Ifin the path of the beam we interpose a prism PRISMATIC ANALYSIS. 37 of glass, as A B c in the accompanying figure, having one of its angles downwards, and so adjuste...« less