The operations involved in taking a photograph may be roughly grouped under two heads. Firstly, the optical part of the business, and secondly, the chemical part. Luckily these two divisions can now be kept quite separate and distinct from one another, so that the amount of impedimenta which the operator takes into the field with him, where the first part of the process is executed, is but a small portion of the necessaries required in taking a photograph. Things were indeed different in the old days of wet collodion plates. The traveller had then to carry all his stock of chemicals with him, for unless the chemical part of the process followed immediately upon the exposure of the sensitive plate in the camera, that plate would be inevitably spoilt. Now, thanks to dry plates, the travelling photographer is quite independent of his bottles, chemicals, and dishes. These are left at home until opportunity occurs when he can introduce them to the plates which he has exposed in his camera during his walks abroad.

The interval which occurs between the two operations of exposure and development may be a few hours, or may be extended to weeks or months. The writer has often during a photographic tour extending over many weeks, left the development of his plates until long after returning to his home, and has seldom found his pictures to suffer by being left uncared for so long. But he by no means recommends this practice, for a slight accident may spoil a negative, and the mischief is not found out until the owner is so far away that another negative taken at the same spot is quite out of the question. Let him cite a case in point. He was staying not long ago on the South Coast, some few miles from Dover. He paid a risk to this town chiefly for the purpose of taking various parts of the old castle, and pictures of certain evidences of the Roman occu-pation of Britain, which abound in the place. From one particular point he obtained a splendid view of the old fortress, and was fortunate in having a lens with him, which just included on his focussing screen the entire view. He took this picture, and followed it by one of the old Pharos which crowns the hill upon which Dover Castle stands. He attached quite as much importance to the one picture as to the other. Luckily he happened to develope his plates on this occasion while still in the neighbourhood, and found to his intense disgust, that Dover Castle was hopelessly jumbled up with the old Roman light-house. He had taken both views on one plate. The accident was soon remedied at the cost of another day's work, and a climb with the apparatus up to the top of the Castle hill. Such a mishap as this can be easily avoided by a simple precaution. The photographer should carry with him a few strips of gummed paper, which he can get for the asking at any post-office. When a plate has been exposed, gum a piece of this paper across the coiner of the shutter which covers it, so that that shutter cannot again be withdrawn without breaking the paper. A memorandum of the subject can also be scribbled with a pencil across the gummed slip. With these few words of caution respecting a difficulty into which it is very easy to fall, we will now enumerate as briefly as possible the necessary precautions to observe in taking a picture.

Let the first attempt be made of a view from a window, if it be only chimney pots. Set the camera up on its stand, uncover the lens and focus the picture as sharply as possible on the ground glass screen provided for the purpose. The focussing cloth is thrown over the head during the operation, and should well cover the camera as well. It is not a bad plan to have attached to the focussing cloth a little elastic loop, which will go over the lens in front. After the view is focussed, put in one of the stops or diaphragms provided with the lens, and notice how the aspect of the picture on the ground glass is modified. It is not so bright as it was, but the details are much sharper than they were before. Use, say, the smallest stop but one; and until experience teaches more familiarity with the camera and its belongings, use no other.

When the view is focussed to satisfaction, cap the lens, throw the ground glass screen out of its place, and retire to the dark room. Here, by the dim light of the red lamp, take a couple of plates out of their containing box, and put them in one of the double backs, taking care that as the back lies open like a book in front of you, that the film, or dull side of the plates is placed downwards. Avoid touching the surface of the plates with the fingers; but brush them over with a flat camel's hair brush kept for the purpose, before inserting the plates in the double back. Close up the plate box, as well as the double slide, and take the latter to the camera. Insert the double back in the groove provided for it, cover the camera with the focussing cloth, and placing your hand underneath, carefully draw the shutter of the slide. Your gelatine plate is now ready for exposure, and when the cap of the lens is removed the light will act upon it. Remove the cap for, say, three seconds, and immediately replace it. You may now reverse the double back, and take another picture, this time letting it have five seconds' exposure. When the two plates are afterwards developed and finished, it will be seen which negative has the brighter appearance, and the power of the lens, as well as the rapidity of the plates employed, can be judged accordingly. One more word about exposure. Get a note-book, and note at first, the details of every exposure made; such as time of day, time of year, state of the weather, and so on By studying this book, side by side with the negatives to which it refers, a great deal may be learnt. Correct exposure is the most important part of the business of photography, and is a thing which can only be learnt by constant practice and attention to details.