Photography 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: CHAPTER I. EABLT BESEABCHES ON THE CHEMICAL ACTION OF THE 80LAH BAYS. It is instructive to trace the progress of a discovery, from the first indica... more »tion of the truth, to the period of its full development, and its application to purposes of ornament or utility. The progress of discovery is ordinarily a slow process, and it often happens that a great fact is allowed to lie dormant for years, or for ages, which, when eventually revived, is found to render a fine interpretation of some of Nature's harmonious phenomena, and to minister to the wants or the pleasures of existence. Photography is peculiarly illustrative of this position. The philosophers of antiquity appear to have had their attention excited by many of the more striking characters of light. Yet we have no account of their having observed any of its chemical influences, although its action on coloured bodies—deepening their colour in some cases, and discharging it in others— must have been of every-day occurrence. The only facts which they have recorded are, that some precious stones, particularly the amethyst and the opal, lost their sparkle by prolonged exposure to the rays of the sun. It has been stated—but on doubtful authority—that the jugglers of India were for many ages in possession of a secret process, by which they were enabled in a brief space to copy the profile of any individual by the action of light. However this may have been, it does not appear that they know anything of such a process in the present day. The alchemists, amidst the multiplicity of their manipulatory processes, in their vain search for the philosopher's stone and the elixir vita, stumbled upon a peculiar combination of silver with chlorine, which they called horn silver—as, by fusion, the white powder they obtained b...« less