To English authors I am principally indebted for that portion of my work relating to Photogenic drawing on paper. To them we owe nearly all the most important improvements in that branch of the art. Besides, it has been but seldom attempted in the United States, and then without any decided success. Of these attempts I shall speak further in the Historical portion of this volume. Every thing essential, therefore, to a complete knowledge of the whole art, comprising all the most recent discoveries and improvements down to the day of publication will be found herein laid down. CONTENTS I. A BRIEF HISTORY OF THE ART. II. THE THEORY ON LIGHT.--THE PHOTOGRAPHIC PRINCIPLE III. SYNOPSIS OF MR. HUNT'S TREATISE ON "THE INFLUENCE OF THE SOLAR RAYS ON COMPOUND BODIES, WITH ESPECIAL REFERENCE TO THEIR PHOTOGRAPHIC APPLICATION." IV. A FEW HINTS AND SUGGESTIONS TO DAGUERREOTYPISTS. V. DAGUERREOTYPE APPARATUS. VI. THE DAGUERREOTYPE PROCESS. VII. PAPER DAGUERREOTYPES.--ETCHING DAGUERREOTYPES. VIII. PHOTOGENIC DRAWING ON PAPER. IX. CALOTYPE AND CHRYSOTYPE. X. CYANOTYPE--ENERGIATYPE--CHROMATYPE--ANTHOTYPE--AMPHITYPE AND "CRAYON DAGUERREOTYPE." XI. ON THE PROBABILITY OF PRODUCING COLORED PICTURES BY THE SOLAR RADIATIONS--PHOTOGRAPHIC DEVIATIONS--LUNAR PICTURES--DRUMMOND LIGHT. XII. ON COLORING DAGUERREOTYPES. XIII. THE PHOTOGRAPHOMETER. INDEX. INTRODUCTION New York, January 27, 1849. E. ANTHONY, ESQ. Dear Sir,--In submitting the accompanying "History and Practice of Photography" to your perusal, and for your approbation, I do so with the utmost confidence in your ability as a practical man, long engaged in the science of which it treats, as well as your knowledge of the sciences generally; as well as your regard for candor. To you, therefore, I leave the decision whether or no I have accomplished my purpose, and produced a work which may not only be of practical benefit to the Daguerrean artist, but of general interest to the reading public, and your decision will influence me in offering it for, or withholding it from, publication. If it meets your approbation, I would most respectfully ask permission to dedicate it to you, subscribing myself, With esteem, Ever truly yours, HENRY H. SNELLING New York, February 1st, 1849. Mr. H. H. SNELLING. Dear Sir--Your note of January 27th, requesting permission to dedicate to me your "History and Practice of Photography," I esteem a high compliment, particularly since I have read the manuscript of your work.