into general use, especially for lamps using high-pressure gas. Numberless patents for the manufacture and improvement of this kind of mantle have been taken out during the last ten years; the most important of these will be dealt with in a later chapter. Attempts have been made to secure greater strength and toughness in mantles in other directions also. The use of metallic wires in the fibre has been suggested; numerous patents deal with mantles ‘strengthened’ by doubling the thread at intervals, and by special methods of weaving the fibre. One method, which follows on the lines of Glamond and Lundgren, proposes[493] the use of mantles made from various oxides mixed with silica, the whole being worked into a paste by use of a gum or soap, from which threads are prepared by pressure; mantles made from these threads are said to be very strong and porous. Another patent[494] protects the manufacture of ‘incandescence bodies’ made from plates or combs prepared from a thread obtained in a rather similar way. A third of these innumerable suggestions recommends a preliminary impregnation of the fabric with an aluminium or magnesium salt,[495] from which the oxide is precipitated on the fabric by a suitable means, impregnation with the ordinary ‘lighting fluid’ being effected after drying. Quite an early patent[496] proposes the impregnation of the prepared mantle, either after or just before burning off, with an alcoholic solution of an organic silicon compound, so that when the mantle is in use a skeleton of silica is formed to ‘strengthen’ the oxide ash. No useful purpose can be served by extending the list of these proposals; enough has been said to indicate the various directions in which so many vain attempts at improvement have been made. [493] Laigle, _D. R. P._ 216871 of December, 1909; see also _D. R. P._ 216877 and 219640. [494] Michaud and Delasson, _D. R. P._ 210640, June, 1909; see also _D. R. P._ 227257. [495] Zdanowich, _E._ 27755, 1908. [496] Jasper, _E._ 30145, 1897.