122 M . Girard on Navigable Canals. 
pers ” are broken up in Paris, and the materials of 
ich they are constructed sold under the name of boat 
w 
a find be superfluous to adduce any further proofs in 
support of this opinion. It is easy to conceive that the 
- boats which should arrive at Paris from the most elevated 
points of the department of the Ardennes, or of the depart~ 
ment of the Coéte-d’Or would not return with so weighty 
cargoes as those they should have brought. e may there- 
fore consider it as an established principle that, in a well 
regulated system of internal navigation, the total weight of 
articles which descend the canals will always be much 
greater than that of the objects which ascend them 
This principle once admitted, the volume of water neces- 
sary for the navigation of canals will be greatly reduced ; 
and the difficulty of sven ae it in sufficient quantity on 
the summit levels of those SS be no ungee an 
passage of boats, and even in case of need, the ey may be 
made to raise a certain volume from the lowest to the high- 
est level of the canal. 
To give an example of this manner of proceeding, let us 
suppose that the draft of water of the boats which descend 
a canal be 1" 20°=(3 feet 10} inches nearly,) and that of 
the boats which ascend 30 centinueter (11 4 inches) only. 
Let us suppose forthier, that the expenditure of water in 
the canal cannot exceed } of the wee t of the boats which 
pore the locks in asian arene substituting these numer- 
plyin Upon daficienty of water which might in some instanees 
prevent the opening of useful canals ; but other, and not 
less important advantages will naturally accrue from the es- 
