‘50 _ TECHNOLOGY. 
projected in the year 1660 by Francois Andreossy, and commenced in 1666 
by Peter Paul Riquet, on the upper Garonne. 
This canal runs across the isthmus which connects the peninsula of Spain 
with France, and which is inclosed between the Pyrenees and the moun- 
tains of the Rhone. It commences in the river Garonne, on the west side 
of the city of Toulouse, and after rising through eight locks reaches the 
river Lers, along which it ascends through thirteen locks to Villefranche. 
From this point, after crossing the Lers by an aqueduct, it reaches the 
summit level by means of five additional locks. These 26 locks make a rise 
of about 220 feet above the level of the Garonne, in a distance of 22 miles. 
I'rom the summit level, after crossing six streams, the canal descends 
through 87 locks to the river Aube; continuing northwards from the city 
of Trebes, it arrives at the main level near Olangac, by another descent 
through 22 locks, after having crossed five other streams, which have their 
sources in the Montagne Noire. The main level continues along the sides 
of the mountains, in many places with aqueducts, crosses two streams, and 
after considerable winding around the Ecurene mountain cuts through a 
ridge of the Malpas hills with a tunnel 575 feet long, which ends with a 
chain of eight locks. Here the canal descends to the plateau of Fonse- 
ranne, whence continuing southwards, it crosses the rivers Orbe, Libron, and 
Agde, and makes its final descent into the Mediterranean. In its approach 
to the latter it crosses a small lake, through which for about four miles it is 
carried between two embankments, the level of the canal being higher than 
that of the lake. 
From the summit level to the Mediterranean the distance is about 114 
miles and the descent 658 feet. The canal has in all 102 locks (one of 
which is circular, with 95 feet diameter, pl. 10, jig. 18), 55 aqueducts, 
numerous dams and dykes, one tunnel, and 92 bridges, in a distance of 
about 136 miles. The lift of the locks is from five to twelve feet. The 
width of the canal is generally 36 feet at bottom and 68 feet at the water- 
line ; the depth is seven feet. The boats used upon it are 90 feet long, from 
18 to 20 feet wide, draw 5 feet 6 inches of water, and carry 100 tons. The 
first trip was made in June, 1681. 
For the supply of water at the summit level feeders were constructed, 
which deserve some attention. Eight small streams of the Black Moun- 
tain (Montagne Notre) were brought together by means of ditches and 
excavations in the rocks into one channel, which was blasted out of the 
rock for a distance of five miles along the mountain, and then carried 
through it by a tunnel 420 feet long and 94 feet wide. At this point it 
is joined by another feeder, the two forming a larger one, which, continu- 
ing its course along the mountains, enters the great reservoir of St. Ferreol. 
From here it takes the direction to the river Gorge, and entering the basin 
of this river, the combined waters are carried by the great feeder to the 
reservoir of the summit level which supplies the whole chain of locks. 
The whole length of these feeders is about 37 miles, although in a direct 
line the distance is not over 16 miles. 
The most important structure on this canal is undoubtedly the great 
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