which are essential to a complete understanding of the art. Many of their methods of operating are entirely different from, and much inferior to, those practised in the United States: their apparatus, also, cannot compare with ours for completeness, utility or simplicity. I shall, therefore, confine myself principally--so far as Photogenic drawing upon metalic plates is concerned--to the methods practised by the most celebrated and experienced operators, drawing upon French and English authority only in cases where I find it essential to the purpose for which I design my work, namely: furnishing a complete system of Photography; such an one as will enable any gentleman, or lady, who may wish to practise the art, for profit or amusement, to do so without the trouble and expense of seeking instruction from professors, which in many cases within my own knowledge has prevented persons from embracing the profession. 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. INTRODUCTION