M. P. S. Girard on Navigable Canals. 313 
serious inconveniencies into which men have been led from 
an ignorance of the true principles. | 
hese inconveniences exist in the canal de Briare, the 
oldest canal in France and the most generally known. 
The number of boats which descended this canal in 1819 
was 3380. These boats were of different dimensions ; but 
we can suppose as a mean term that, loaded, their draft of 
water was 0.66 metres (261 inches;) they are 24 metres 
(79 feet) long, and 3.50 metres (i123 feet) wide. © 
The mean cargo of one of these boats, is consequently 
about fifty tons. 
The whole weight of articles brought to Paris, on this 
canal, during the year 1819, was, therefore, about 170,000 
tons. 
The far greater portion of these boats were demolished 
at Paris, and those that ascend the canal go empty. At all 
events it is certain that the goods transported from the 
Seine to the Loire, do not weigh one hundredth part so 
much as those which come from the Loire to the Seine. 
The whole length of the canal de Briare, from the di- 
viding point to the River Loing, is 34582 metres (6934.4 
rods, or 21.67 miles); its descent, which-is 78.74 metres 
(258.4 feet,) is surmounted by 27 locks, the lift of some of 
which is near 4 metres (1325 feet). 4 
It is a long time since it’ has been observed that there 
was a great loss of water, occasioned by the passage 
through the locks where the lift and fall was 80 considera- 
, and so disproportionate to the draft of water of the 
boats destined to pass through them. But, such is the state 
of things : in order to appreciate the consequences, let us 
first determine what quantity of water would be absolutely 
eae for the circulation of 170,000 tons of merchan- 
nal de re. 
Now it isevident thatif the number of locks had been quad- 
Tupled, their mean lift would have been reduced to about 75 
centimetres, (2;4°, feet ;) and if the draft of water of the 
‘oaded boats had been carried to 1,5,°, metres (4,;°2, feet,) 
it is also evident that in consequence of the diminution in 
the lift, and the augmentation of the draft of the’ boats, the 
1350 boats, which together would carry as much as the 
3380 boats which descended to the Seine in 1819, that is 
to say, which would displace the same quantity of 170.000 
tons of water, would elevate, by their descent, the half of 
Vou. VII.—No. 2. 40 
