. Lighthouse construction and illumination; . ount of the Neapolitan earthquake of1857, found that the maximum amplitude of the wave, oramount of shove in a horizontal du^ection, did not exceedthree or four inches. The observed effects, as is well known, vary from a meretremor to such a violent disturbance as to result in the over-throw of whole cities; and, as may be readily imagined, evenin comparatively slight shocks the delicate apparatus in a 232 LIGHTHOUSE ILLUMINATION. lighthouse is peculiarly liable to derangement, and instancesare recorded in which the lamp glasses have been shaken of
. Lighthouse construction and illumination; . ount of the Neapolitan earthquake of1857, found that the maximum amplitude of the wave, oramount of shove in a horizontal du^ection, did not exceedthree or four inches. The observed effects, as is well known, vary from a meretremor to such a violent disturbance as to result in the over-throw of whole cities; and, as may be readily imagined, evenin comparatively slight shocks the delicate apparatus in a 232 LIGHTHOUSE ILLUMINATION. lighthouse is peculiarly liable to derangement, and instancesare recorded in which the lamp glasses have been shaken offand the lamps extinguished. In 1867, the Board of Trade asked Messrs. Stevenson toadvise as to establishing a lightliouse system on the coasts ofJapan, which being a country peculiarly subject to earthquakes,they requested them specially to consider in what way theanticipated injury to the apparatus could be mitigated. Tomeet the difficulty thus raised, Mr. David Stevenson devisedan Aseismatic-joint in the table supporting the apparatus and. Fig. 135. machine, so contrived as to admit of a certain amount ofhorizontal movement taking place in the building withoutaffecting the table on wliich the apparatus rests, the ideabeing that in some horizontal plane the connection betweenthe apparatus and the building should be cut through andseparated, so that the sudden motion of the lower part shouldnot be directly communicated to the superincumbent 135 is a section in which the upper table bearing the mSCELLANEOUS SUBJECTS. 233 holophotal reflectors is sliowu in hatched lines. This tablerests on spherical bell metal balls, contained in cups formedin the upper and lower tables, and Fig. 136 is a plan of thelower table, showing the three points of support. The same
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
