Farther Inquiries Into the Changes Induced on Atmospheric Air; By the Germination of Seeds, the Vegetation of Plants, and the Respiration of Animals

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated.1811 Excerpt: ... Sect. IV Of the Physical and Chemical Agency of Light, in promoting the Colouration of Plants. 411. So far we have spoken of the colours of plants, as arising from variations in their chemical constitution alone; and these variations we have attributed to the decomposition of their saline compounds, by the agency of solar light. We have next to inquire into the manner in which light exerts this action, a subject of very nice and difficult investigation, but the importance of which will, we hope, furnish an apology for the apparent temerity of our attempt, even although we should fail in its execution. 412. Besides this chemical action, which light has been shewn to exert, we have also to consider its property of imparting colour; for when it has been said that the predominance of acid or alkaline matter renders the vegetable juices red or green, it must be understood to mean only, that such a state or constitution of those juices is thereby induced, as, in the language of Sir Isaac Newton, enables them, more or less, to reflect or transmit the red, or greenmaking rays of light. We do not, however, propose to go far into the consideration of these subjects, but to select and exhibit such facts only, as force themselves on our notice, by the near connection which they seem to have with the more immediate objects of our research. 413. Since the great sera in science, created by the genius of Newton, who first decomposed the solar beam, and thus Untwisted all the shining robe of day," it has been considered, that " colours are not qualifications of light, derived from refractions or reflexions of natural bodies (as was generally believed), but original and connate properties, which, in divers rays, exhibit divers colours ." By means of the prism, Sir Isaac New...