282 STUDIES IN BIRD-MIGRATION 



Brethren, and I took up my residence on the Eddy- 

 stone on 1 8th September 1901, and remained there until 

 19th October. 



The Eddystone rocks consist of three contiguous 

 reefs, which He 14 miles south-west of Plymouth, and 

 are 10 miles from the nearest point of the mainland. 

 The central reef is the most extensive, its exposed 

 length at low water being some 150 yards, while its 

 jagged crest then rises about 1 5 feet above the sea. 

 At high water all the rocks are either submerged or 

 have their highest points awash. The lighthouse stands 

 isolated at the northern extremity of the main reef, and 

 is a massive structure, 168 feet in height. On the 

 adjacent reef to the north, and about 40 yards distant, 

 stands the basal portion of Smeaton's historic tower, 

 completed in 1758 and in use down to 1882, a fitting 

 monument to the genius of the founder of the science 

 of modern lighthouse-engineering. The gallery, which 

 was the scene of my vigils, and my perambulations too, for 

 the base of the tower is submerged at all states of the 

 tide, is 130 feet above the sea. The illuminating 

 apparatus consists of a double series of dioptric lenses, 

 one placed above the other, each furnished with a six- 

 wick lamp, and develops the enormous power of 80,000 

 candles. In clear weather, however, only one lamp is 

 used. The lisjht is concentrated into twelve brilliant 

 beams, arranged in pairs, which revolve slowly, taking 

 three minutes to make a complete circuit. 



Landing on the rock is somewhat exciting work for 

 a novice, and is effected from a surf-boat towed out by 

 the relief steamer for the purpose. This boat approaches 

 the rock at low water, and anchors as near the base of 

 the tower as the surf which eddies around it will permit. 



