Note 30 — SECTION V. THE VALUE OF HIS DISCOVERIES.
Reading edition
The illuminating apparatus at Dungeness is one of what is termed the sixth order, 300 millimetres (about 12 inches) in diameter. Mr. Chance constructed one for Souter Point of the third order, one metre (nearly 40 inches) in diameter, with special arrangements for giving artificial divergence to the beam in a vertical direction, in order to obviate the danger arising from the luminous point not being always precisely in the same spot. It has also additional contrivances for utilizing the back light. Similar arrangements were made for the South Foreland lights, which are also of the third order; and every portion of the machinery and apparatus is in duplicate in case of accident, and the double force can be employed in times of fog.