Papers on the Comparative Merits of the Catoptric and Dioptric or Catadioptric Systems of Light-House Illumination; And Other Subjects Relating to AIDS to Navigation
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1861 edition. Excerpt: ...to present the photometric results obtained from different lenses of the four orders of dioptric apparatus. Lenticular apparatus of the first order. (A.)--First order lenticular apparatus for a fixed light, with accessory catoptric part Lustre or brilliancy of the dioptric drum =360 burners. Mean brilliancy of mirrors--7 upper zone8=80) fc 4 lower zones = 40 j Total amount of brilliancy=480" Calculation of the useful effect. 1st. The dioptric drum illuminating equally the whole of the horizon, (except about 26, being computed the amount of space occupied by the frames of the apparatus, and that of the lantern, )=360 burners X 20,000' = 7,200,000 2d. 7 zones of upper mirrors =80 burners X 20,000'= 1,600,000 3d. 4 zones of lower mirrors, omitted for one-eighth of the circumference, for the necessary passage of the keepers, =40 burners X 17,500'= 700,000 Total of useful effect 9,500,000 ., t 9,500,000 Economical effect = =----_ 750 gramines= 12,667. 0 Notwithstanding the decided advantages which the catadioptric zones present, compared to the mirrors, we may, by reason of their economy, prefer, under some circumstances, the second combination to the first for lenticular apparatus of the first order. If the apparatus illuminate only three-fourths of the circumference of the horizon, the useful effect will be reduced to 7,200,000 To which must be added the effect of the reflector occupying the vacant space in the dioptric drum, one-fifth (360 burners X 5,000'= 360,000 Useful effect of the apparatus, for 270= 7,560,000 j + A. i - 7,560,000 1st order, economical ettect =--, n Aon 750 grammes=10,080 (a1)--First order lenticular apparatus for a fixed UqJd, with accessory catadioptric part. Lustre or brilliancy of the dioptric drum...
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