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Subterraneous

flash, tin, lamps and results

SUBTERRANEOUS PHOTOGRAPHY.—The chief difficulty in underground photography lies, as would naturally be imagined, in the illumination. To do this satisfactorily by artificial means requires much care and thought. Mr. J. C. Bur row, writing of his experiences in photographing the workings of a Cornwall tin mine says " After pre liminary trials with cameras of various dimensions a half plate was chosen on account of its lightness, portability, and moderate size, the latter being specially important in confined situations. Double plate holders were employed, for, although there was no danger of light when the candles were extinguished, and plates could be safely changed, yet it was found impossible to keep the hands clean. A Zeiss Anastigmat, Series III., was used and gave beautiful results. A sliding tripod was also found very useful as the camera had often to be tilted at an angle of 6o degs., and the front leg tied to a rock to prevent overbalancing.

" It is needless to detail the incidents attending the transport of apparatus from surface to the bottom of an inclined shaft half a mile below. Some were unpleasant, others amusing.

" Readers intending to attempt underground photog raphy must not be discouraged when staggering through the semi-darkness with a hydrogen cylinder under one arm and a pair of lime-light burners under the other, if they fall headlong into a pool of water by the side of the level. Nor must they lose their self-control when,

after carefully selecting the driest spot available to open the magnesium powder tin for recharging the lamps, a • flush ' of water from some unknown source falls into the tin as soon as the cover is off, instantly dropping the curtain most effectually upon the re mainder of the day's programme.

" The writer, after repeated unsatis factory experiments with different flash lamps, designed a pair of triple flash ar rangements, which have proved exceed ingly satisfactory. The high tempera tures of the deep mines caused camera and lens to be covered with condensed vapor for some time after the scene of operations was reached, a source of much bother.

" A state of readiness having been arrived at, the word to `light up' pro duced a powerful flash from the lamps and ribbons simultaneously. The lime lights were previously at their maxi mum intensity. An exposure of from two to four seconds generally gave the best results. If everything appeared favorable in the strong light, another subject was sought, for a second exposure in the same place on the same day rarely gave good results, owing to the ' fog ' caused by the products of the combustion of the magnesium."