M. Girard on Navigable Canals. 123 
iablishment of the relation here assigned between the draft 
of water of the boats and the lift of tlie canal-locks. By aug- 
menting that draft of water, and by diminishing that lift, it 
will be possible to transport the same quantity of goods on 
narrower canals; the ground occupied by the canals will 
therefore be less, and consequently cost less- purchase 
money,* while the loss of water by evaporation will dimin- 
ish in the same proportion. 
The manceuvreing of the gates will be much easier, and 
may be confided to the boatmen, as is practised on the small 
canals in England, by which means the wages and lodgment 
of the Lock-keepers may he saved. 
The pressure of water on the sides and bottoms of the, 
locks being much less will cause less damage, and conse- 
quently render the repairs less frequent and costly. By 
this means canal navigation willbe no longer exposed to 
those frequent and long interruptions which have heretofore 
been necessary for the purpose of repairs. 
Finally, narrower boats with a greater draft of water, 
will offer less resistance when tracked,* and as they may 
be decked, their cargoes will be more secure than in ordi- 
nary flat-bottomed boats. 
In a future memoir I shall develope more fully the Jast 
advantages which I have here pointed out. In concluding 
this, I shall only remark that the discovery of lock naviga- 
tion is still a recent discovery, which has been less appre- 
ciated by the general results of its application to water com- 
munications, than by its visible result of a difficulty over- 
come. ‘The mind requires some reflection to seize the ad- 
vantages of a system of small locks placed one after another 
at greater or less intervals, while the imagination is forcibly 
struck by the manceuvreing ofa lock ofa considerable lift. 
In the fourteenth century, when artillery was first invent- 
ed, they began by making cannons to throw balls of two to 
three hundred pounds weight. Notwithstanding their pro- 
digious effect, their unwieldly mass soon compelled the 
abandonment of their use. There now remain none of 
* Perhaps this advantage will be counterbalanced by the extra cost of ex- 
cayation.— Translator. es 
* This proposition does not yet appear to be clearly demonstrated, and 
before giving it entire credence, I am disposed to wait the further illustra- 
tions of the author.—Translator. 
