MINES, PHOTOGRAPHY IN With the advent of the dry plate, the modern lens and the actinic flash powders, photography in mines has become much more easy. The bunch of magnesium ribbon, lime-light apparatus and portable lamps have all been superseded. In gassy mines, the use of flashlight mixtures is inadmissible, but it answers well, for example, in the tin mines of Cornwall, which are deep, hot, smoky, wet and dirty, with grease, mud, and slime in abundance, in some places stagnant air in which the tallow candles will not burn, in others a draught so strong that naked candles cannot be kept alight. The hanging walls from which water drips from every jagged point of rock, the slippery footwalls, open stopes, deep gunnies, perpendicular ladders with iron staves, the low, narrow levels, etc., etc., present the most unpromising conditions for successful photography. The miners work by the light of tallow candles stuck in a lump of clay which adheres to the hard hat they wear, or against the rock on arriving at the scene of their operations. These candles give out little illumination, but plenty of smoke. The angular rocks of a dull brown, non-actinic colour require powerful illuminants to bring out their structure. The mine photographer should be something of a mining engineer so as to grasp intelligently the idea which the photograph is intended to illustrate. In Cornwall he becomes familiar with mineral lodes and cross-courses, shafts, levels and winzes, air currents and ventilation. The principal features of mining, or the natural position of the miner at his work, must not be sacrificed in order to compose an artistic or sensational picture. Neither must he be fastidious about his dress, hands or apparatus, nor object to crawl on his hands and knees over the rough rocks, through narrow openings, and oftentimes dangerous places. The camera must be strong and well made, capable of enduring without serious damage the inevitable contact with points of rock. Double dark-slides filled with plates sufficient for the day's use should be taken. Plates could be changed underground as absolute darkness exists when the candles are extinguished, and it is quite easy to feel to do this work, but other conditions are not favourable to this course. It rarely happens that more than six plates can be exposed in one " shift," and as a rule only one exposure can be made in one place by reason of the smoke caused by the combustion of magnesium. At least three lenses are necessary, respectively of io in., 7 in., and 5 in. focal lengths. The greatest trouble with lenses is caused by moisture condensing on their cold surfaces, and in order to avoid this as much as possible they should be carried in the inner pocket of the flannel shirt next the skin. As soon as the cap is put
on after focusing, condensation immediately covers the front of the lens, and this can scarcely be wondered at in a temperature exceeding ioo° F. (about 38° C.), with steam rising from the water which runs at one's feet, or dropping from the jagged points of rock above the camera. A piece of soft silk kept in the trousers pocket should be used to wipe the lenses. In some places, where the heat is almost unbearable, drawers are the only garments worn by the miners at work.
In the past magnesium ribbon and the oxy hydrogen light were used ; now, after repeated experiments, triple flash lamps of great power have been found to give the best results. Prom two to four of these lamps are generally sufficient, with an exposure of about three or four seconds. By a judicious use of lamps some unique lighting effects can be obtained, but special attention must be given to air currents, which, if possible, should be upward, or else towards the camera. When it is not possible to photograph a gunnies (a large chamber) from one standpoint, it often answers to move the camera to the other end ; this is probably due to the admission of good air at one end driving the foul air to the other, which, although not perceptible to the eye, is revealed by the lens and produces a foggy effect. Flash candles are useful when placed behind a rock so as not to produce a glare in the lens.
The most sensitive plates are not the best for the purpose, because of their tendency to fog in forced development ; there is usually more than enough of fog surrounding the object itself. A plate of medium speed, say ioo H. and D., backed, has been found to possess all the qualities necessary.
For photographing coal mines, the general arrangements are the same as in tin mining, but naked lights can only be used in those few collieries that are free from gas ; otherwise, the difficulties are not so great, the mines are drier, the coal surfaces reflect the light, and very little trouble is experienced with coal dust.
In the slate mines of North Wales and other places, where there are vast excavated chambers a hundred fathoms from the surface, the con ditions are easier still, the air is good, and it is a question only of sufficient lamps to light up the dark caverns.
The subsequent printing from the negative is a matter of ordinary practice, but the picture should represent as clearly as possible the colour of the rock or material photographed. By the carbon process, for instance, bluish tones representing slate can easily be obtained, or brown tints will depict the darker rocks in Cornish mines, and blue-black the coal deposits.
J. C. B.