. Lighthouse construction and illumination; . of the other sources of lightemployed for that purpose. rig. 122 is a section of the Argand burner, in wliich t isthe cylindrical space through the centre of the wick for theI ^ ^ I passage of the second air current, and c the glass chimney. It is an inchin diameter, and the central air spaceis f inch diameter. Fig. 25 (page60) shows the arrangement of theArgand lamp used in the NorthernLighthouse Service. Frcsnel Burner.—When Tresneldesigned his dioptric apparatus he atonce saw the necessity for a greaterintensity of flame than could be gotfrom th
. Lighthouse construction and illumination; . of the other sources of lightemployed for that purpose. rig. 122 is a section of the Argand burner, in wliich t isthe cylindrical space through the centre of the wick for theI ^ ^ I passage of the second air current, and c the glass chimney. It is an inchin diameter, and the central air spaceis f inch diameter. Fig. 25 (page60) shows the arrangement of theArgand lamp used in the NorthernLighthouse Service. Frcsnel Burner.—When Tresneldesigned his dioptric apparatus he atonce saw the necessity for a greaterintensity of flame than could be gotfrom the Argand, and, with the assist-ance of Arago and Mathieu, he devisedmultiple wick burners, previouslysuggested by Eumford; Figs. 123Fig. 122. and 124 are plan and section of one of liis burners, with four concentric wicks, the spacesbetween them being passages which allow air to pass up to ((\ -S ^ SOURCES OF ILLUMINATION. 205 the inner wicks; G, C, C, C, are the rack handles forraising and lowering the wicks \ A B \s> one of the ducts. wliicli lead oil to the four wicks; L, L, L, are smaU platesof tin by which the burners are soldered together, and placedso as not to liinder the free passage of air to the flame. Theair spaces are about \ inch wide. The chimney is carried bythe gallery R B, and is surmounted by a sheet-iron cylinder,which serves to give it a greater length, and has a smalldamper fixed in it, capable of being turned by a handle forregulating the current of air. In order to keep the burnercool and protect it from the excessive heat produced, the oilis supplied in superabundant quantity, so as to overflow thewicks. Fresnel used two, three, and four concentric wicks;Mr. Alan Stevenson, in 1843, introduced a fifth; and has more recently adopted a sixth. It will be observed that the leading principle of tliis, asof all other lighthouse burners introduced since Argandstime, whether for burning vegetable, animal, or mineral oUs,is his double current. 2
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
