120 Some Account of the Northern Light-houses. 



ni^ht of terror, when its commerce was ruined, and its ships 

 were disabled, even if we did not know the fact, we should con- 

 clude that it was unlikely that any attention would be paid to the 

 improvementof the French light-houses. Accordingly, only about 

 ten or twelve years since, when the Corps Royal des Pouts et 

 Chaussees, et des Mines, under which the light-houses and har- 

 bours of France are placed, began to improve their lights, they 

 resolved upon laying aside the very imperfect and insignificant 

 reflectors then in use. They adopted a modification of the fa- 

 mous Buffon's burning-glass, as prepared by the late celebrated 

 M. Fresnel, and which we believe to be similar or identical with 

 the burning-glass of Dr (now Sir David) Brewster, who, in 

 1811 or 1812, had described a lens of this description, in the 

 Edinburgh Encyclopaedia. In the application of this instrument 

 to light-houses, Fresnel, with that liberality of character which 

 greatly endeared him to all who knew him, disclaims any merit 

 as the first who had suggested its application to light-house pur- 

 poses. Such a proposal had been made by an optician of Lon- 

 don to Mr Smeaton in 1759, as mentioned in his Narrative, 

 page 156, for illuminating the Eddystone light-house, but was 

 not adopted by that eminent engineer. M. Fresnel mentions 

 that lenses had been used in England so far back as 1789, in 

 the lower light-room at Portland Island, but, from whatever 

 cause, they have since been laid aside. In the year 1820, in the 

 course of some investigations connected with the Trigonome- 

 trical Survey of Great Britain, and conducted by a deputation 

 of persons eminent in science from London and Paris, M. Fres- 

 nel, from the French side of the Channel, exhibited, by means 

 of his lens and a large lamp, a powerful light, which was ob- 

 served by the English across the Channel. 



The brilliancy of this light so struck Lieut.-Colonel Colby 

 of the Royal Engineers, who was engaged in these observations, 

 that, with his usual kindness, and zeal for the advancement of 

 science, he immediately corresponded with Mr Stevenson, en- 

 gineer for the Northern Light-houses, as to its probable use 

 upon the Scottish coast. Mr Stevenson, no less zealous for im- 

 provement, communicated with Mr Adie, the principal optician 

 in Edinburgh, and with Dr Brewster, then engaged in optical 

 researches, but without coming to any practical result. In 



