CANAL 



1145 



CANAL 



the delays and dangers experienced in journey- 

 ing over rough trails and roadways and across 

 deserts and mountains by means of animal 

 power, led to the building of canals for naviga- 

 tion many hundreds of years before railroads 

 solved the problem of rapid transportation. 

 This article discusses only the canal for navi- 

 gation. Drainage and irrigation channels are 

 described under the headings DRAINAGE and 

 IRRIGATION. The Chicago Drainage Canal (see 

 CHICAGO DRAINAGE CANAL) is an important 

 example of a channel excavated for the purpose 

 of carrying away the sewage of a city. 



In Egypt, Assyria, India and China naviga- 

 tion canals were in operation long before the 

 Christian Era, and Nebuchadnezzar, the great 

 Babylonian ruler of the sixth century B. c., 

 restored a canal that classic writers say was 

 originally built eleven centuries before his time. 

 This was the royal canal of Babylon, connect- 

 ing the Tigris and the Euphrates rivers. It is 

 an interesting tradition that a predecessor of 

 the present Suez Canal (which see), joining the 

 Nile River to the Red Sea, was begun about 

 600 B. c. by an Egyptian king ; this is said to 

 have been destroyed in A. D. 767 by a Moham- 

 medan caliph. In the thirteenth century the 

 Chinese constructed the most important work 

 of its kind after the beginning of the Christian 

 Era the Grand Canal, connecting the Yang- 

 tse-kiang and the Pei-ho. This canal is 650 

 miles long and from five to six feet deep. 



In comparison, canal building in Europe 

 developed somewhat tardily, the present mag- 

 nificent systems dating from about the twelfth 

 century. The invention of the canal lock, 

 however, in 1481, the honor of which is claimed 

 both by Italy and Holland, gave new impetus to 

 the construction of artificial watercourses, and 

 Europe has a canal mileage at the present time 

 of about 13,300. The total for the world is 

 about 26,000, representing an expenditure of 

 over two billion dollars, and over half of this 

 is in a few countries of the continent of Europe. 

 Statistics for the world's important canals may 

 be found in the table at the end of this article. 



Details of Construction. In railroad build- 

 ing the track may run up or down grade, but 

 the course of a canal must consist of one or 

 more level sections, or reaches. The Cape Cod 

 Canal, which cuts through a narrow strip of 

 land where the Cape and the Massachusetts 

 mainland join, is an example of a waterway 

 which connects two points on a single water 

 level (see CAPE COD CANAL). Canals built 

 over a route of different levels, like the Erie, 



consist of several reaches, the adjoining ex- 

 tremities of which are usually connected by 

 locks. A lock is a chamber with stone or con- 

 crete side walls and water-tight gates at each 

 end. In passing from a lower to a higher level 

 a vessel goes through the gates at the lower 

 end, and floats into the chamber. The lower 

 gates are then closed and the valves in the 

 sides or bottom of the lock are opened, allow- 

 ing the water from the higher level to flow in. 

 When the water in the lock has reached the 

 level of that above the upper gates, these gates 

 are opened and the boat continues its journey. 



The dimensions of a canal are determined by 

 the size of the vessels which are expected to use 

 it. It must be wide enough at the surface 

 and bottom to permit any two boats to pass 

 without touching each other, and the depth 

 should be at least one and one-half feet greater 

 than the draft of the largest vessels that navi- 

 gate it. The canal bed is always made flat. 

 When the channel is excavated through soft 

 earth the sides slope outward from the bottom, 

 and the harder the material the steeper the 

 banks. It is customary to cut the banks per- 

 pendicular, or nearly so, when the canal runs 

 through rocks. Power drills and explosives are 

 used to break up rock. 



Embankments or aqueducts are built to carry 

 canals across valleys; culverts are provided to 

 carry streams beneath them, and these water- 

 ways are crossed by bridges wherever they are 

 intercepted by ordinary traffic routes. The 

 aqueduct usually takes the form of a masonry- 

 arch bridge, the top of which is made into a 

 channel or trough to conduct the water. Steel 

 is now used to some extent in constructing 

 these troughs. 



Canals of the United States. The advan- 

 tages that would result from building canals 

 in a new and sparsely-settled country were fore- 

 seen by George Washington and other states- 

 men of the early national period. A canal 

 ' around the rapids of the Connecticut River, at 

 South Hadley, Mass., the first artificial water- 

 way built in America, was completed in 1793, 

 but the first important work of this kind was 

 the Erie Canal, across New York state, begun 

 in 1817. Its completion in 1825 was a signifi- 

 cant event in the economic history of the 

 country ; it made a city of the town of Buffalo, 

 at its western terminus, and was largely re- 

 sponsible for the early commercial supremacy 

 of New York City. The subsequent improve- 

 ments made on this canal and on other canals 

 constructed later in New York state are fully 



