DO PHYSICAL GEOGEAPHY OF THE SEA. 



reckoned among the seven wonders of the world, and its several 

 stories, rising on marble columns to the height of 400 feet, 

 must have presented an imposing spectacle, but I strongly 

 suspect that the rude brazier on the summit of the majestic 

 pile bore the same proportion to the lighthouse lanterns of our 

 time as the wretched coasting-craft of the ancient Greeks to the 

 ocean steamers of the present day. Among the names of those 

 who have contributed most effectually to the progress of marine 

 illumination Argand, Borda, and Fresnel are conspicuous. The 

 hollow cylindrical wick of the first was a sudden and immense ad- 

 vance in the art of economical and effective illumination. The 

 second, by his invention of tLe parabolic mirror, multiplied the 

 effect of the unassisted flame by 450, and the refracting lens of 

 Fresnel so admirably concentrates the light as to project its warn- 

 ing beams to the wonderful distance of thirty or thirty-five miles 



In former ages the efforts of man to provide a refuge to the 

 mariner from the fury of the raging gale were feeble and in- 

 significant. Content with the harbours that nature had provided, 

 it was then thought quite sufficient to line a river-bank with 

 quays or to enclose a natural pond by walls. The idea of raising 

 colossal breakwaters by casting whole quarries into the deep, or 

 of extending artificial promontories far into the bosom of the 

 ocean, is of modern date, and would have appeared chimerical 

 not only to the ancients but to our fathers not a century ago. 

 The first great work of this description is the famous break- 

 water planned by De Cessart in 1783, and terminated in 

 1853, which has converted the open roadstead of Cherbourg 

 into a land-locked harbour. Eising from a depth of 40 feet 

 at low spring tides, on a coast where the floods attain a height 

 of 19 feet, it opposes a front of 12,700 feet to the fury of the 

 storm, and carries 250 pieces of the heaviest cannon on its for- 

 midable brow. 



It far surpasses in extent and boldness of construction the 

 breakwater at Plymouth, nor will it be eclipsed by the moles now 

 forming at Portland, Holyhead, and Alderney; but although 

 it is a more impressive spectacle to see man struggling with the 

 ocean and producing calmness and shelter in the midst of the 

 raging storm, than to contemplate his operations where he has 

 no such adversaries to subdue, still such buildings as those just 

 described are neither the largest nor the most expensive works 



