COAST DIKES. 403 
Draining of Lincolashire Fens. 
The draining of the Lincolnshire fens in England, which 
has converted about 400,000 acres of marsh, pool, and tide- 
washed flat into ploughland and pasturage, is a work, or rather 
series of works, of great magnitude, and it possesses much eco- 
nomical, and, indeed, no trifling geographical, importance. Its 
plans and methods were, at least in part, borrowed from the 
example of like improvements in Holland, and it is, in difii- 
culty and extent, inferior to works executed for the same pur- 
pose on the opposite coast of the North Sea, by Dutch, Frisie, 
and Low German engineers. The space I can devote to such 
operations will be better employed in describing the latter, and 
I content myself with the simple statement I have already made 
of the quantity of worthless and even pestilential land which 
has been rendered both productive and salubrious in Lincoln- 
subsidiary works of great extent, has a cutting half amile long, 1,000 feet wide, 
and from 150 to 200 feet deep.—Horrmann, Hncyclopedie, 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 Hrnst-August-Stollen, 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 
métres, or about 100,000,000 cubic yards, and those of the Ganges Canal, which, 
with its branches, had 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 pyra- 
mid. 
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. . 
In an article on recent internal improvements in England, in the London 
Quarterly Review for January, 1858, it is stated that in a single rock-cutting on 
the Liverpool and Manchester railway, 480,000 cubic yards of stone were 
