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means, sea, apparatus, bottom, cylinder, light and water

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SUBMARINE PHOTOGRAPHY.—What the bottom of the sea looks like is a conundrum which people have tried to solve to the best of their ability during recent years. Of course pho tography has been called in to render its valuable assistance. What has been done in this direction is given by Dr. J. E. Rombouts in the following article, translated and condensed from De Natuur : " The deep sea explorations and dredgings of late years have certainly shed much light thereon, and have acquainted us with much which, earlier, we would not have suspected could exist at the bottom of the sea.

" Imagination had pictured the bottom of the sea, at least at great depths, as a wilder ness, wherein nothing was to be found save the remains of animals which had lived at the sur face. Owing to the absence of sunlight it was supposed no life could exist and no color develop.

" We know from what has already been published concerning the deep sea explorations that the state of things at the bottom of the sea is entirely different. We know that there, as well as on the earth's surface, a great variety obtains. That great apparently unin habited areas alternate with densely populated forest regions— sparkling with every color. No wonder that the attempt has been made to record, by photographic means, that which is to be found beneath the surface.

" This was not to be thought of when we were entirely depend ent upon sunlight—but at present we have in the electric and mag nesium lights means by which to picture even the most obscure places, and by means of which photography may wrest from the sea her secrets.

"The first endeavors to accomplish this object were made by Regnard.' In his work entitled ' La Vie dans les Eaux,' he gives a description of which the substance follows : "In the first place the lens most be of a class by which objects both near and remote may be photographed. So-called sharp focus ing in the ground glass is not necessary—but one must be able to photograph all objects, no matter at what distance from the objective. In using such a lens under water it must be borne in mind that light rays under water are not exactly in the same manner as in the at mosphere.

" An arrangement must be provided by which the lens can be uncapped and capped at a given instant, and the whole apparatus must be able to resist any injury from the pressure of water to which it is subjected. Regnard's apparatus, of which we give a view, consists of a copper cylinder closed above and below by copper plates; the upper plate rests upon a rubber ring, and can be screwed down securely. In this cylinder is a camera, C, with a sensitive plate—which can be exposed by means of a shutter.

" Below the cylinder is a tripod which upon lowering the ap paratus rests upon the bottom. The objective which is in the lower end of the cylinder is thus always at a uniform distance from the bot tom. Especial means must be taken to overcome the tendency of the apparatus to rise. The pressure of the water, even at a depth of io metres is about equivalent to that of the atmosphere.

The pressure is overcome by means of a balloon, B, which is filled with air, and which is connected with the interior of the camera by a tube. When the cock, R, is open as the appar atus sinks, the balloon, B, is compressed and there is an equilibrium of the pressure within and without the camera. The shutter is opened and closed by means of clock work, the speed of which is regulated by means of a fan, V.

"The illumination is by electric light furnished by accumulators which are contained in a space around the cylinder. Two incandescent lamps stand on each side of the objective, and are provided with strong glass protectors. It is evident that the accumulators would soon be exhausted in case they were continuously employed. An arrangement is provided by which the current is turned on the moment the exposure is made. The light is thus used' only during the exposure. The apparatus is lowered overboard by means of a cable." Fig. 447 shows the apparatus. S is the plate, M the shutter, LL the electric lights operated, by means of an accumulator. Whether the apparatus produced good photographs is not known to the author, he never having seen the results.

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