HARBOR AND COAST IMPROVEMEITTS. 391 



CTiniary expenditure, than would now be required for the building 

 of the tomb of Cheops. It is computed that the great pyramid, 

 the solid contents of which when complete were about 3,000,000 

 cubic yards, could be erected for a million of pounds sterling. The 

 breakwater at Cherbourg, founded in rough water sixty feet deep, 

 at an average distance of more than two miles from the shore, 

 contains double the mass of the pyramid, and many a compara- 

 tively unimportant canal has been constructed at twice the cost 

 which would now build that stupendous monument. 



The description of works of harbor and coast improvement 

 which have only an economical value, not a true geographical 

 importance, does not come within the plan of the present volume, 

 and in treating this branch of my subject, I shall confine myself 

 to such as are designed either to gain new soil by excluding the 

 waters from grounds which they had permanently or occasionally 

 covered, or to resist new encroachments of the sea upon the land.* 



* Some notice of great works executed by man in foreign lands, and prob- 

 ably not generally familiar to my readers, may, however, prove not uninter- 

 esting. 



The deaaguadero, or canal constructed by the Viceroy Revillagigedo to pre- 

 vent the inundation of the City of Mexico by the lakes in its vicinity, besides 

 subsidiary works of great extent, has a cutting half a mile long, 1,000 feet 

 wide, and from 150 to 200 feet deep. — Hoffman, En^ydopwdie, art. Mexico. 



The adit which drains the mines of Gwennap in Cornwall, with its branches, 

 is thirty miles long. Those of the silver mines of Saxony are scarcely less 

 extensive, and the Ernst-August-StolUn, or great drain of the mines of the 

 Harz, is fifteen miles long. 



The excavations for the Suez Canal were computed at 75,000,000 cubic 

 metres, or about 100,000,000 cubic yards, and those of the Ganges Canal, 

 which, with its branches, has a length of 3,000 miles, amount to nearly the 

 same quantity. 



The quarries at Maestricht have undermined a space of sixteen miles by 

 six, or more than two American townships, and the catacombs of Rome, in 

 part at least originally quarries, have a lineal extent of five hundred and 

 fifty miles. The catacombs of Paris required the excavation of 13,000,000 

 cubic yards of stone, or more than four times the volume of the great pyramid. 



The excavations for the Mt. Cenis tunnel, eight miles in length, wholly 

 through solid rock, amounted to more than 900,000 cubic yards, and 16,000,- 

 000 of brick were employed for the lining and backing. The St. Gothard tim- 

 nel, now (1882) just completed, is a still more surprising monument of human 

 enterprise and perseverance. For cost and other details connected with this 

 ■stupendous work, see the admirable Reports published by the Swiss Govern- 

 ment during its construction. 



In an article on recent internal improvements in England, in the London 



