VIII. LIGHTHOUSES, &C. 455 



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 conies 

 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 30 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.) 



Modem Apparatus. 



No. 11. Great annular lens, of the first order, l-10 m in diameter, Messrs. 

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

 Barbier and Fenestre as a specimen of high class workmanship. Each ring is 

 one single piece ; the joints which divide the rings are inclined according to 

 the direction of the ray refracted. The lens is mounted on a pedestal, and 

 revolves around any horizontal axis. 



No. 12. Lenticular panel, dioptric and catadioptric, for flashing lights of 

 the second class, planned by the head engineer, Allard, and constructed by 

 Mr. Henry Lepaute, 1876. 



This panel forms part of an apparatus intended for the Pilier lighthouse, 

 situated at the mouth of the Loire, and of which the tower has just been 

 rebuilt. The character given to it in 1829 has been preserved; it is a fixed 

 light varied by flashes every four minutes To produce this character a fixed 

 light apparatus has been adopted, of which two sectors of Jth horizon, 

 opposed to one another, are replaced by perfect annular lenses ; it revolves 

 at the rate of one turn in eight minutes. In order that the two kinds of 

 lenses may be adjusted upon the edges, and have a common pinion-jack, the 

 focal distance, which is 0-700 m for the fixed lenses, has been reduced to 

 0'647 m for the annular lenses. The focal lamp has five concentric wicks, 

 instead of four, as usual in lamps of the second class, because the light, being 

 coloured red in certain directions, it was thought necessary to increase its 

 in tenseness. 



This panel shows several novel arrangements, some of which are now 

 applied for the first time. 



1st. In the central or dioptric parts of the section, the joints that divide 

 the elements, and therefore the lower sides of these elements, instead of being 

 horizontal, are inclined according to the direction of the ray refracted. This 

 system has several advantages : it does away with a triangular part of glass 

 which is useless, and thus lessens the weight of the apparatus ; it reduces in a 

 large proportion the loss of light caused by horizontal joints ; it makes less 

 harsh, and consequently less fragile, the outer angles of the elements, and, 

 besides, it diminishes their projection, thus enabling the dioptric lens to 

 acquire a greater height. 



