Fig. 30.
Fig. 31.
Argand Lamps used in Reflectors. The flame generally used in reflectors, is from an Argand fountain-lamp, whose wick is an inch in diameter. Much care is bestowed upon the manufacture of the lamps for the Northern Lighthouses, which sometimes have their burners tipped with silver to prevent wasting by the great heat which is evolved. The burners are also fitted with a sliding apparatus, accurately formed, by which they may be removed from the interior of the mirror at the time of cleaning them, and returned exactly to the same place, and locked by means of a key. This arrangement, which is shewn in [figs. 28], [29], and [30], is very important, as it insures the burner always being in the focus, and does not require that the reflector be lifted out of its place every time it is cleaned; so that, when once carefully set and screwed down to the frame, it is never altered. In these figs. a a a represents one of the reflectors, b is the burner, and c a cylindric fountain, which contains 24 ounces of oil. The oil-pipe, the fountain c for supplying oil, and the burner b, are connected with the rectangular frame d, which is moveable in a vertical direction upon the guide-rods e and f, by which it can be let down, so that the burner may be lowered out of the reflector, by simply turning the handle g (as will be more fully understood by examining [figs. 28] and [29]), which has the effect of forcing a thread (like that of a screw) on the outside of the guide into a groove in the frame, or withdrawing it, and thus allows it to slide down or locks it at pleasure. An aperture of an elliptical form, measuring about two inches by three, is cut in the upper and lower part of the reflector, the lower serving for the free egress and ingress of the burner, and the upper, to which the copper tube h is attached, serving for ventilation; i shews a cross section and a back view of the main bar of the chandelier or frame on which the reflectors are ranged, each being made to rest on knobs of brass, one of which, as seen at k k, is soldered to the brass band l, that clasps the exterior of the reflector. [Fig. 28] is a section of the reflector a a, shewing the position of the burner b, with the glass chimney b′, and oil-cup l, which receives any oil that may drop from the lamp. [Fig. 30] shews the apparatus for moving the lamp up and down, so as to remove it from the reflector at the time of cleaning it. In the diagram ([fig. 30]) the fountain c is moved partly down; d d shews the rectangular frame on which the burner is mounted, e e the elongated socket-guides through which the guide-rods slide, and f the guide-rod, connected with the perforated sockets on which the checking-handle g slides. The oil-cup l (covered with a lid and wick-holder, as shewn in [fig. 31]) also serves as a frost-lamp during the long nights of winter, when the oil is apt to turn thick. It is attached to the lower part of the oil-tube by the arm h; and is lighted about an hour before sunset, so as to prepare the reflector lamp for lighting at the proper time. The communication between the burner and the fountain is easily opened or shut in the burners used in the Scotch Lighthouses, by simply giving the fountain a turn of one quadrant of the horizon round its own vertical axis by means of the round knob at its top, and thereby moving a simple slide-valve, which shuts off the communication between the fountain-tube and lamp-tube. By this mode, the oil is cut off about fifteen minutes before extinguishing the lights, so that when that is done, the burner is quite free of oil.
Fig. 32.
It would needlessly occupy much time and space to describe the various means (many of them sufficiently clumsy) which have been employed, and in many places are still in use, for raising and depressing the wick; it will be enough to say, that they all involve some application of the rack and pinion. Arrangements for Raising or lowering the Argand Wick. I shall, therefore, only describe the method (invented, it is believed, by M. Verzy) which is adopted in all the Lighthouses in the district of the Commissioners of Northern Lights. The arrangement is as follows (see [figs. 32], [33], [34], [35], [36]):—The inner tube t of the burner is enclosed by a strong tube s, which fits to it tightly, so as not to be easily moved. This strong tube has a spiral groove cut on its outer or convex surface. The wick-holder has two small pegs projecting from it, the one on the inside (not seen), and the other on the outside at a ([fig. 33]). That on the inside works in the spiral groove of the tube S ([figs. 32] and [33]), already described as embracing the inner tube t; and all that is required for raising the wick is to make the wick-holder turn round on its vertical axis. This is effected by means of the small external peg a of the wick-holder ([fig. 33]), which moves in a vertical slit a ([figs. 32] and [34]), cut in a tube standing in the burner, and concentric with it, and which also moves freely round its axis. Small knobs n n ([figs. 32], [34], and [36]), at the top of this tube, fit into a notch in the upper ring of the gallery, which supports the glass chimney. By turning this gallery g (see [figs. 33] and [36]), therefore, motion is given to the tube, with its knobs n n, whose vertical slit a (while it holds the external peg of the wick-holder, and also turns it round along with it) permits that peg a to slide upwards or downwards, and thus the wick-holder rises or falls, according as its own internal peg moves up or down the spiral groove in the tube S. In [fig. 32], C shews the glass chimney resting on the gallery g g.
Fig. 33.