The object'of the author in writing the present book has been not to provide a guide or text book for those desiring to practise the art of photography, but rather to givein a popular manner an outline of its operations for the reader who seeks to know something about photography, without necessarily wanting to practise it. We believe there are many people who like to acquire knowledge of a subject simply for the sake of knowing in a general way How it's done. It is for such people we have written this book, and we have endeavoured to divest it of detailed technicalities. The task has not been an easy one, and it would have been much less troublesome for the author to proceed on the usual lines of describing the processes with the completeness necessary to lenable them to be worked from the instructions given. That would have meant a much larger book, for which probably there is no real need, as there are so many excellent treatises on the subject already published. The author has endeavoured to carry out the aim of the publishers of this series, and it the book should fall into the hands of some who are already well up in the subject, and who may consider there is little that is new in it, let them remember that there are many people who, not having had their advan tage, may find such a book as this interesting and possibly useful.