1889.] on Beacon Lights and Fog Signals. 431 



but of larger dimensions, as suggested by the late Mr. Thomas 

 Stevenson, for obtaining greater efficiency with the larger flamed 

 luminaries recently adopted. The apparatus is provided with two 

 Trinity House imj)roved mineral oil burners, and Las a minimum 

 intensity for clear weather of about 80,000 candle units, and a maxi- 

 mum intensity for thick weather of about 513,000 candle units. The 

 character of the light is Double Flashing, showing two flashes, each 

 of four seconds duration, in quick succession at periods of one minute. 

 The flashes of this light, and those of a light lately completed at 

 about eight nautical miles from it, on Round Island, are the most 

 intense yet attained with oil flames for beacon lights ; and it may be 

 stated that, with no other illuminant at present known to science, 

 could these results be carried out within the space available at 

 the Bishop rock, and under the circumstances attending that work. 

 The fog signal recently adopted at this station, in lieu of the bell, is 

 by the electrical explosion of four-ounce charges of gun-cotton, at 

 intervals of five minutes. The apparatus provided for this form of 

 fog signal is shown on the diagram. It consists of a wrought-iron 

 crane (attached to the lantern) which is raised and lowered by a worm 

 wheel and pinion. When the crane is lowered, its end reaches near 

 the gallery, where the lightkeeper suspends the charge of gun-cotton, 

 with its detonator attached, to the electric cable, which is carried 

 along the crane and through the roof of the lantern to a dynamo 

 electric firing machine. Aiter suspending the charge, the jib of the 

 crane is raised to its upper position, when the charge is fired nearly 

 vertically over the glazing of the lantern, and thus without causing 

 damage to it. 



The large and heavy optical apparatus is rotated automatically 

 by compressed air, which is stored in two vertical steel reservoirs, 

 fixed at the centre of the tower. The air is comj^ressed by a small 

 Davey Safety Motor. A winch, worked by the compressed air, is 

 fixed on the lantern gallery for landing the lightkeepers, stores, &c. 



The numerous outlying shoals surrounding the shores of this 

 country, particularly ofl:' the east coast, were an early cause of anxiety 

 to those responsible for the guidance of mariners. And in addition 

 to buoys as sea marks by day, floating lights, as guides by night, 

 were found to be a necessity. The first light-vessel was moored at 

 the Nore Sand in 1732, and another near the Dudgeon Shoal in 1736. 

 We have here a model of the latter vessel, from which we may judge 

 of the pluck and hardihood of the crews who manned them ; especi- 

 ally when we remember that there were no chain cables in those 

 days ; the vessel having to be moored with a cable of hemp, which, 

 owing to the constant chafing, occasionally parted during winter 

 storms, when, to save their lives, the crew had to put out another 

 anchor if possible, or set such storm canvas as they could, to keep her 

 off a lee shore, and endeavour to reach a place of safety. The illumi- 

 nating apparatus of these vessels consisted of a small lantern, and 



