. Lighthouse construction and illumination; . Fiff. 142. Fig. Fig. 144. understood on looking at the 142 and 143 are elevation andsection of reflectors, which, parallelisethe rays in the vertical plane onlyBCD are paraboloidal strips for act-ing on the waves of sound producedby the anterior half of the whistle, orother radiant placed in the focus. EF G are similar strips for parallelis-ing the waves proceeding from theposterior half of the radiant. H Hare hollow cones for reflecting forwardthe rays parallelised by E F G. Fig. 144 represents the holophonewhich reflects the
. Lighthouse construction and illumination; . Fiff. 142. Fig. Fig. 144. understood on looking at the 142 and 143 are elevation andsection of reflectors, which, parallelisethe rays in the vertical plane onlyBCD are paraboloidal strips for act-ing on the waves of sound producedby the anterior half of the whistle, orother radiant placed in the focus. EF G are similar strips for parallelis-ing the waves proceeding from theposterior half of the radiant. H Hare hollow cones for reflecting forwardthe rays parallelised by E F G. Fig. 144 represents the holophonewhich reflects the sound in every plane,and H H are the side reflectors, whichin this case, instead of being conicalare plane, and placed at an angle of45° with the lateral beams of sound. FOG-SIGNALS. 261 A is the whistle, bell, siren, or whatever radiant is to be whistle may either be placed vertically, as shown in the dramngs,or horizontally, should that position be found preferable. In order toreduce the loss of sound passing off by the vibrations of the metalitse
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
