A tape measure with metric scale of measurements on one side and feet and inches on the other is most important. Two small, light waterproof cases could be constructed and packed with scientific instruments, data, and spare clothing and yet not exceed the weight limit of flotation. In transit by pack-train these two cases would form but one mule load.
PHOTOGRAPHIC—From the experience gained in several fields of exploration it seems to me that the voyager should limit himself to one small-sized camera, which he can always have with him, and then carry a duplicate of it, soldered in tin, in the baggage. The duplicate need not be equipped with as expensive a lens and shutter as the camera carried for work; 31/4 x 41/4 is a good size. Nothing larger than 3 1/4 x 5 1/2 is advised. We carried the 3A special Kodak and found it a light, strong, and effective instrument. It seems to me that the ideal form of instrument would be one with a front board large enough to contain an adapter fitted for three lenses. For the 3 1/4 x 4 1/4:
One lens 4 or 4 1/2 focus
One lens 6 or 7 focus
One lens telephoto or telecentric 9 to 12 focus
The camera should be made of metal and fitted with focal-plane shutter and direct view-finder.
A sole leather case with shoulder-strap should contain the camera and lenses, with an extra roll of films, all within instant reach, so that a lens could be changed without any loss of time.
Plates, of course, are the best, but their weight and frailty, with difficulty of handling, rule them out of the question. The roll film is the best, as the film pack sticks together and the stubs pull off in the moist, hot climate. The films should be purchased in rolls of six exposures, each roll in a tin, the cover sealed with surgical tape. Twelve of these tubes should be soldered in a tin box. In places where the air is charged with moisture a roll of films should not be left in a camera over twenty-four hours.
Tank development is best for the field. The tanks provided for developing by the Kodak Company are best for fixing also. A nest of tanks would be a convenience; one tank should be kept separate for the fixing-bath. As suggested in the Kodak circular, for tropical development a large-size tank can be used for holding the freezing mixture of hypo. This same tank would become the fixing tank after development. In the rainy season it is a difficult matter to dry films. Development in the field, with washing water at 80 degrees F., is a patience-trying operation. It has occurred to me that a small air-pump with a supply of chloride of calcium in small tubes might solve the problem of preserving films in the tropics. The air-pump and supply of chloride of calcium would not be as heavy or bulky as the tanks and powders needed for development. By means of the air-pump the films could be sealed in tin tubes free from moisture and kept thus until arrival at home or at a city where the air was fairly dry and cold water for washing could be had.
While I cordially agree with most of the views expressed by Mr. Fiala, there are some as to which I disagree; for instance, we came very strongly to the conclusion, in descending the Duvida, where bulk was of great consequence, that the films should be in rolls of ten or twelve exposures. I doubt whether the four-barrel gun would be practical; but this is a matter of personal taste.
APPENDIX C.
My Letter of May 1 to General Lauro Muller