The London Engineer publishes a description of a lamp for this purpose, invented by Mr. Heinke, of London, a gentleman well known in connection with diving apparatuses. This invention consists firstly, in an improved mode of supplying the lamps with air and also of carrying off the products of combustion; and, secondly, in adapting to such lamps reflectors, condensers, or lenses, which throw the light with groat intensity in the direction required. The first of these objects $ effected by placing the lamp (which may be of any suitable construction, provided it gives a considerable amount of light) within a double cylindrical or other conveniently shaped casing, which is provided with an annular chamber or space, formed by piacing one casing of smaller diameter within another of larger diameter, leaving tin annular space. Xhe illustration shows a vertical section of the lamp. It is preferred to make the casing or body of sheet copper, and it is composed of two cylinders, a and r, placed concentrically, one within the other, so as to leave an annular space, c, between them. The foot of the lamp is composed of the same material, and is also made hollow; as at d, d. The internal part of the hollow foot is perforated with small holes, e, e, for the purpose of admitting air from the annular space, c, to the interior of the lamp. The casing has any convenient number of condensing lenses fitted to suitable openings made in the casing, as shown at/,/,/; and if required, reflectors may be adapted in such a manner to the lamp as to throw the light through the condensing lenses. It will be seen that there are two lenses, / /, adapted to the sides of the casing, for the purpose of throwing the light forward in a horizontal direction. There is also another condensing lens, /, adapted to the foot of the apparatus, and above the light is placed a horizontal metal reflector, g, which will throw the light down through the condensing lens, and thereby cast a brilliant light on anything below. The lamp, h, is of the ordinary ar-gand kind, and is supplied with oil from the resevoir, i, which is made of an annular form, for the purpose of allowing the light from the flame of the lamp to pass through to the condensing lens, / below. The lamp is secured in vertical slotted guides, j, js fixed to the sides of the casing; it is of course provided with a glass chimney for the purpose of steadying the flame, and the reflector, g% is placed on this glass chimney, and may be secured at any suitable altitude by means of spring clips, as is well understood. The gaseous products of combustion pass up the glass chimney from the flame in to the trumpet-mouth, Jc, of the vertical tube, which communicates with the Jiose or flexible pipe, -t, above, the connection between the two pipes being effectel by means of a screw joint at the top of the dome cover of the apparatus, as seen at m. This cover is screwed on to the top of the apparatus, a leather or other washer, w, being placed on the flange, by which the two parts are united. Air to support combustion is supplied to the lamp down the flexible tube or hose, which is adapted to a short conical branch pipe secured to the sides of the casing and made to communicate with the annular space between the inner and outer casings. The two circles of this branch pipe, p, o, are dotted in the figure, being in front of the lamp. The apparatus is suspended by means of cords or chains.
This article was originally published with the title "Apparatus for Illuminating Objects under Water"