ISLAND. 



perfect lens in the centre, surrounded by successively 

 diminishing segments of larger lenses. Square mir- 

 rors are placed both above and below, in many rows, 

 at such angles as shall reflect the light upon the sur- 

 face of the sea. 



The whole combination of refraction and reflection 

 has the effect of producing a most intense glare, when 

 the eye of the beholder is immediately opposite the 

 centre of any one of the lenses. The power of the 

 light, indeed, may be imagined, from the fact that it 

 shines with a strong and vivid glare at Ilfracombe, 

 which is twenty-two miles distant. But this inten- 

 sity of light is only momentary : by means of wheel- 

 work, the motive power of which is a weight-and- 

 chain pulley, like that of a clock, the eight-sided 

 frame revolves around the light, with a uniform mo- 

 tion, performing the complete circle in sixteen minutes. 

 Thus a period of two minutes elapses from one mo- 

 ment of greatest intensity to the next ; the interval 

 being occupied by a gradual diminution of the appa- 

 rent light, till the dimmest point is attained ; and 

 then a gradual increase to the brightest. At a great 

 distance there occurs an interval of total obscurity ; 

 but this is only because the rays are too feeble to be 

 appreciable so far. Within a circle of a few miles 

 the light never quite disappears. 



The fatality which the lanterns of lighthouses occa- 

 sion to birds has been often mentioned ; it is, how- 

 ever, a curious circumstance. Lundy Light, it appears, 

 is responsible for its full share of these casualties. 



