542 SEC. 12. APPLIED MECHANICS. 



concentric circular wicks, each having an inner and an outer draught. 

 It gave great intensity, but the solderings of the burner were destroyed 

 by the heat. About 1800, the watchmaker Carcel invented the lamp that 

 bears his name, and in which the oil at the bottom is forced up by a pump 

 towards the burner above which it overflows. This invention subsequently 

 led to the solution of the problem of lamps with many wicks. Consequently, 

 when Arago and Fresnel began, in 1819, their experiments with lamps, they 

 forced up the burner oil in superabundance so as to replenish it, and thus avoid 

 the inconvenience met with by Guyton-Morvau. The first trial took place 

 in September 1819 with two-wicked and three-wicked burners, constructed 

 after Fresnel' s designs. After several deliberations, chiefly respecting the 

 width to be adopted for the draught between the wicks, they succeeded in 

 constructing a four- wicked burner that gave good results. It was tried 12th 

 May 1820, in presence of the Lighthouse Committee. The burner exhibited 

 under No. 8 is one of those that were constructed according to this first 

 type. 



The two- wick burner, No. 9, was constructed by Henry-Lepaute in 1845, 

 for the lighthouse of Schevening in Holland. It has an outer cylinder for 

 dividing the draught generated between the glass and the burner, and 

 throwing back a part of it upon the light. It is the first application of this 

 cylinder which exists in all modern burners. 



The five-wick burner, No. 10, is a model of those now constructed for 

 using mineral oil in the French lighthouses. It contains an appendage 

 through which the oil must pass before reaching the upper part of the 

 burner. This said piece, of which the arrangements were invented by 

 M. Denechaux, acting engineer in ordinary at the lighthouse depot, is 

 intended to secure a continuous level, and comprises three tubes, juxtaposed, 

 and open on the upper part at the proper height ; the central tube springs 

 from the small reservoir which forms the base of the burner, and in which 

 the oil is forced by the machinery of the lamp ; this oil, having ho other exit, 

 rises in the tube, and, arriving at the top, flows into the second tube, which 

 carries it into the annular spaces containing the wicks ; these it fills while 

 keeping the same level as in the lateral appendage. As the quantity of oil 

 forced up by the lamp is greater than the consumption, the excess comes 

 down into the large reservoir of the lamp by flowing into the third tube over a 

 fall rather higher than that cleared by the oil in reaching the burner. A 

 horizontal disk of 20 millimetres diameter rises, at the height of 21 milli- 

 metres, above the central draught tube, and an outer cylinder divides in two 

 the draught created between the burner and the glass. It is upon this outer 

 cylinder that the glass-holder stands. In this burner the empty spaces between 

 the wicks, intended for air passages, are 5~ millimetres wide, while the spaces 

 that contain the wicks are only 4^ mill. In the burners constructed up to the 

 present time, both widths are of 5 mill. ; this new arrangement seems to give 

 better results. The burner has, besides, on its upper part, a graduated shape, 

 so that each wick is placed about 2 millimetres below the one which precedes 

 it towards the centre. This arrangement, as yet adopted only for the 

 Pilier lighthouse, exhibited under No. 12. has been found necessary since the 

 burners, in each order of lighthouses, have had one burner added to them, and 

 therefore are wider. Its object is to lower the edge of the burner, in reference 

 to the centre of the light, so as to reduce as much as possible the portion 

 of light obscured by this edge in the lower part of the lenses. (See descrip- 

 tion of apparatus, No. 12.) 



Modern Apparatus. 



No. 11. Great annular lens, of the first order, M0 m in diameter, Messrs. 

 Barbier and Fenestre, constructors, 1867. This lens was constructed by Messrs. 



