Stereographs.
Stereographic views are most useful for confused masses of objects, such as a field of ruins. And if there are no moving parts there is no need to take them simultaneously. By shifting the camera to one side, and taking a second plate, a perfect stereograph is obtained; and whereever the chance is not to be repeated, and two plates are taken to ensure success, a shift should be made so that both may be used together. The amount of shift varies with the distance; for near objects the distance between the eyes, 2½ or 3 inches, may suffice; for a general view a foot or 2 feet is better, so as to give more solidity than is naturally seen. Small objects must not be shifted by rotating the object if there are sharp shadows, as such are falsified by the turning; otherwise a slight twist of the object does for the second view.
Developing.
It is undesirable to leave developing till long afterwards. In general all negatives should be developed the evening after they are exposed; thus the future exposures can be regulated, any defective plates can be repeated, and deterioration and risks due to keeping are avoided. In the variety of developers the old pyrogallic acid remains still one of the most reliable. The fanciful instructions about proportions are exploded at once by a glance at the table compiled by Captain Abney. By adopting the mean proportions of all the makers, which is 1 soda carbonate, 1 soda sulphite, and 20 water, as a stock solution, and adding about 3 grains per ¼ plate of pyrogallic when using, very uniformly good results are obtained with short exposures. Of course long exposures require bromide; but that is very seldom needful. Extra local developing by tilting the dish, or painting with a brush, is useful in case of shadows. Tabloid developers are best avoided, as they cause delay in dissolving; and made-up solutions are cumbrous and expensive. The quantities needed can always be put out by guess, taking ¼ of an 8-ounce bottle at a time of soda salts, and weighing pyrogallic for once to know the look of it. For hyposulphite of soda fill the bottle ⅓ full of crystals, and fill up with water. If a less strong and more graded picture is needed then glycin seems preferable to pyrogallic acid.
No dark room is needed; developing can always be done in the evening. A red paper envelope split at the bottom and put round the chimney of an ordinary lamp, will best screen the light. The diffused light of a room will not hurt slow plates in developing, and a sheet of brown paper over each tray makes all safe. A first soak in weak pyrogallic solution, to flatten the films, is best before developing. For washing where water may be scarce it suffices to have a row of six soup plates of water, and to pass each film through each plate for five minutes, so completing the washing of each in half an hour. A zinc box with 6 or 8 divisions, shifting the negatives forward through each division, will also work well. For drying it is best to have a row of pins along the edge of a shelf, and then to punch out a small hole in a corner of the film and hang it up, with the gelatine face under the shelf to keep dust from it. A dusty evening in Egypt will leave each film like a piece of sandpaper; and in case of this the films can be afterwards rapidly washed under a stream of water, wiping with a lump of cotton-wool. This will be enough without resoaking the film. Owing to the dryness of the air in Egypt films generally curl up in drying, and if forcibly flattened they are liable to strip. They are best packed in lots of about 50, coiled up together as a cylinder, and wrapped in a turn of paper. When in England they can be flattened out by being left near an open window in damp weather, or dipped in water and left to dry. For quick drying, films may with care be stood inside a fender before a fire, and finished over a lamp chimney. I have thus dried them in about twenty minutes.
CHAPTER VIII
PRESERVATION OF OBJECTS
The preservation of the objects that are found is a necessary duty of the finder. To disclose things only to destroy them, when a more skilful or patient worker might have added them to the world’s treasures, is a hideous fault. And the excavator must be ready for all emergencies, for all classes of objects in all stages of decay, and deal with each without delays, and often with scanty and unsuitable means at hand for their treatment. Some familiarity with chemistry and physics and properties of materials, is one of the first requisites for an excavator. All this applies in a lesser degree to the difficulties of transport, which is also part of the preservation of the antiquities.
As conditions so infinitely vary it is useless to lay down any fixed rules for treatment. Such rules would hinder the use of common sense, which is essential to success. But examples of how different materials are affected, and how difficulties have been met, will lead to the excavator thinking out a fit treatment for each case as it arises. In all this we are stating field practice only, and not dealing with museum methods, which differ by having far more command of resources, and by not having to deal with any of the troublesome cases which do not survive to reach a museum.
Stone.