A TREATISE ON THE CHEMICAL CHANGES PRODUCED BY SOLAR RADIATION, AND THE PRODUCTION OF PICTURES FROM NATURE, BY THE DAGUERREOTYPE, CALOTYPE, AND OTHER PHOTOGRAPHIC PROCESSES. BY ROBERT HUNT, PROFESSOR OF MECHANICAL SCIENCE IN THE MUSEUM OF PRACTICAL GEOLOGY, With Additions by the American Editor. NEW YORK: 8. D. HUMPHREY, 297 BROADWAY. ENTERED, according to Act of Congress, in the year 1851, by S. D. HUMPHREY, in the Clerk's Office of the District Court of the Southern District of New York. Epatean 561 9-23-41 PREFACE TO THE AMERICAN EDITION. In a country where the Heliographic Science is exerting such powerful influence as it is now creating in America, it is highly desirable that the means for pushing investigation should be within the reach of every ambitious mind. The world is indebted to our country for the most eminently successful Daguerreotypes, and we should be also foremost in our exertions to develope new truths, and diffuse the result of our experience and research; at the same time we should employ to the best advantage the experience of others. In doing so, I have taken advantage of the present opportunity to present to the American public one of the most valuable productions from the pen of one of England's most gifted philosophers. To comment upon this work would not add in the least to its importance, while by placing it within the hands of every Daguerreian, each can glean from its pages such information as to enable him to form his own conclusion. America presents the means of furnishing constantly such information as may tend to the elevation of this beautiful art. As one I will mention the Daguerreian Journal, which makes its semi-monthly appearance, bearing with it the latest developments or improvements. This is the oldest publication of the kind in the world. Since the author's preface was written, proof of another improvement has presented itself. This is the Heliochrome, a process of producing the colours of nature, discovered by M. Niepce de St. Victor, a Frenchman. Mr. Hill, of the State of New York, still lays claim to a similar discovery. Of the justice, to my knowledge, no one has become fully satisfied by ocular demonstration. Yet it is hoped he has all that he has led the public to expect. No pains have been spared on my part to render the American edition worthy of the patronage of every lover of the science in this country. S. D. HUMPHREY. New York, January, 1852. |