MAGNESIUM. 



521 



bodies luminous, a fact already availed of for 

 an interesting lecture-room experiment. Thus, 

 a series of wide tubes containing different phos- 

 phorescent substances, and all appearing white, 

 are placed within a box [lined with black ?] : 

 upon throwing upon the tubes the magnesium 

 light, each suddenly glows with its specific 

 phosphorescent color. 



The magnesium light has the advantage of 

 being a portable one. The wire can even be 

 carried in a coil hi the pocket and lighted with 

 a match, and the trouble involved in such case 

 of portioning out the wire, at the rate of its 

 consumption, may yet be obviated by the devis- 

 ing of very compact forms of the magnesium 

 lamp. One among the greatest advantages of 

 the new light for use in apartments, halls, etc., 

 consists in the circumstance that the material 

 burned disengages no gas or vapor of any sort. 

 The only product of the combustion of a pure 

 wire is, of course, the inert and harmless oxide, 

 magnesia ; but even this, escaping, it appears, 

 in flocculent form, is said to form a dense white 

 smoke, or rather cloud of ash, which has its 

 inconveniences for certain situations. It has 

 been proposed to force this smoke, or ash, by 

 mechanical means, into dilute sulphuric acid ; 

 but the plan appears not as yet to have been 

 carried out. With the exception of the possi- 

 ble diffusion of a dust of magnesia in the air of 

 a room lighted by the metal, no agent delete- 

 rious to the health could be given off by the 

 latter, and, in any case, nothing is emitted cal- 

 culated to tarnish or injure articles of furniture 

 or ornament. 



Magnesium Lamps: Improved Forms of Ma- 

 terial. Since the discovery that the combus- 

 tion is unproved by flattening the magnesium 

 wire into ribbon, the latter form is coining into 

 general use. In the production of a magne- 

 sium lamp, a first essential is, some apparatus 

 that will pay out the wire or ribbon at the pre- 

 cise rate of the combustion. Mr. Wm. Mather, 

 of Salford, and Mr. F. W. Hart, of Kingsland, 

 each produced a lamp in which the wire was 

 delivered by hand from a reel, being then 

 guided between rollers and through a tube, and, 

 in order to avoid risk of extinction, into the 

 flame of a spirit-lamp. To this arrangement, 

 Mr. Alonzo Grant, of Nottingham, affixed 

 clock-work to secure automatic delivery of the 

 wire ; and the apparatus, in this form, has 

 proved tolerably successful. 



A chief difficulty, in the early xise of the 

 light, arose from the risk of sudden extinction, 

 due probably to some foreign material or flaw 

 in the wire. With improvements in the prep- 

 aration of both metal and wire, this difficulty 

 has already been greatly reduced, a single wire 

 sometimes burning without going out for half 

 an hour. But the risks of extinction are very 

 greatly lessened by using together two or three 

 strands of ribbon or wire, one of these being 

 likely, if occasion require, to relight the other. 

 In this way the spirit-lamp may be dispensed 

 with : and one of Mr. Grant's lamps, paying 



out a double strand, has burned two hours 

 without cessation. 



Prof. Carlevaris, of Italy, has been investi- 

 gating the production of the magnesium light, 

 and experimenting with a view to secure the 

 best form of the material. He declares that 

 when magnesium wire is ignited in air or oxy- 

 gen, the greatest luminous effect is not mani- 

 fested until after a certain quantity of oxide 

 has been formed and raised by the heat to an 

 excessively high temperature. The most in- 

 tense heat' of the flame leaves the magnesian 

 oxide still solid and unaffected, but the solid 

 particles of oxide serve hi the flame the same 

 purpose of evolving light as do the carbon 

 particles in the flames of ordinary lights, and 

 platinum or lime in the oxy-hydrogen flame. To 

 raise this oxide to the temperature necessary to 

 give the greatest light, it should be presented 

 to the flame in as small a quantity and as large 

 a volume as possible. To this end, Carlevaris 

 at first introduced into the oxy-hydrogen flame 

 (or, better still, it appears, into that given by a 

 jet of illuminating gas and atmospheric air 

 with one-tenth oxygen), magnesia, and, in sub- 

 sequent experiments, its carbonate ; while, final- 

 ly, he found the best effects from exposing to 

 such flame a piece of the chloride of magne- 

 sium (and, as one account states,) in contact 

 with a piece of carbon ; the chloride is rapidly 

 decomposed, furnishing the spongy oxide. In 

 this way a light of still greater actinic power 

 than that of metallic magnesium was obtained. 



Applications of the Magnesium Light. Some 

 of these have already been incidentally alluded 

 to. It is stated that the magnesium lamp is 

 likely soon to become, in Paris and London, a 

 regular article of furniture in every silk-mer- 

 chant's show-room. In winter and foggy days, 

 when the ordinary light fails to show delicate 

 distinctions of color, and in the night, the 

 magnesium light at once exhibits all hues as 

 truly as a clear daylight. The same quality fits 

 the light for the exhibition of colored photo- 

 graphs, and we may add, of course, for night 

 exhibition in picture-galleries, and wherever it is 

 desirable to present truthfully, by an artificial 

 light, delicate and various hues of color. 



Good photographic pictures have, in some 

 instances, already been secured by the unaided 

 magnesium light, and the latter has also been 

 used to assist an imperfect chemical action of 

 daylight. Prof. Piazzi Smyth early tested both 

 the illuminating and the photographic powers 

 of the light in the interior of the Egyptian 

 pyramids, and in case of the former, at least, 

 with astonishing success. More recently, the 

 light has been applied to photographing sections 

 of the interior of lead mines, in order to show the 

 quantity of ore exposed and the different veins 

 the miners are following. Capt. Bamber, R. N., 

 of the island of Jersey, has been engaged hi 

 adapting the magnesium light to use in mines 

 and tunnels, and for railways. By means of a 

 spring, a train of wheels, and a governor, he 

 supplies the ribbon to a burner within a small 



