M. Girard on Navigable Canals. 105 
the Canal of Languedoc, attributes these formule to Mr. 
Clauzade, one of the engineers of that canal ; they were 
n such a manner as to give an easy mathud of icaaing 
in all cases, the quantity of water expended by the passage 
of one boat or more tire a system of locks, the falls of 
which are severally known 
But does there not exist a necessary relation between 
this fall, the quantity of water expended for the passage of 
boats, and the draft of wee of the boats which ascend or 
descend through the lock 
This is a question which, ee, its importance, 
has never yet been treated, and w propose to resolve. 
To reduce the question to its ae simple expression, we 
shall suppose ; Ist, that the boat is to pass from one level 
r by a single lock. 
” adly, That the boats are of a prismatic form, and that 
their dimensions are such that the interval which separates 
their sides from the sides of the lock, when compared with 
the space Ae by the boat, may be neglected without 
sensible e 
etS represent the horizontal section of the lock and the 
boat ; 
, ‘the lift of the lock, that is, wad difference of level be- 
tween the two basins which it unit 
ts the draft of water of a boat which ascends the Jock. 
, the draft of water of a boat which descends. — 
The manceuvre of passing a boat from a lower to a higher 
level consists in 
Ist, Drawing the boat into the — through the lower 
gate, which is closed sie — is 
2d, Introducing, by ni wll means, from the 
higher basin into the lock a > qaintiey of water sufficient to 
ee the two ee to the same level ; 
pening the upper gate of the lock, and pes ag 
boat ibeounted into the upper basin. 
Hence we see that, to effect this passage, an in order to 
raise the surface of the water in the lock to a sie with that 
in the upper basin, it is necessary to draw from that basin 
a prism of water = as =, Wiad is equal to the horizon 
Vou. IV.....No. 
eases 
