104 M. Girard on Navigable Canals. 
from the lower locks to the upper ones, by means of the 
steam engine, the water which has been expended by the 
passage of the boats. 
It would then be rendering an eminent service, and hasten 
the developement of a general system of inland navigation 
in France, if we could point out any means by which the 
expense of water could be diminished, without changing the 
common mode of construction of the Joc , which is found- 
ed on so simple a law of Hydrostatics that we must perhaps 
despair of ever being able to substitute any thing more per- 
fect in its stea 
rom the first period of the invention of locks and gates, 
it was easy to calculate the quantity of water necessary to be 
drawn from an upper level or reservoir, to raise or lower a 
boat, when once the difference of levels between two con- 
tiguous locks or basins was given. 
Subsequently, the French engincers agitated the question 
of determining i in Fare manner the oR ha of water from the 
reservoir ibe 
ced it immediate st :cession fter another. The dif- 
ferent suppositions ‘that were eda: by changing the state 
of the question, gave rise to many aiforonr opinions, of 
which Mr. Gauthey first rendered an account, in a memoir 
published i in 1783, among the memoirs of the Academy of 
- Dijon, and which is also inserted in the 3d Vol. of his 
ks 
The engineers of the canal of Languedoc, who were 
deeply interested in the exact appreciation of the expence 
the dividing reservoirs of thatcanal, and who had every 
facility for repeating the experiments, in the two hypotheses. 
of single locks, and of several locks contiguous to each oth- 
er, occupied themselves specially with the ebieth an gave 
divers solutions of the problems, as ma a me- 
moir of Mr. Ducros, inspector general Pe Chi E neering 
(Ponts et Tae BI blished in the year Engines 
having pointed out, as fee a ch Gauthey had done before 
the order in which the boats which ascend and descend a 
eanal, should succeed oan other in order to occasion ne 
useless waste of water, Mr. Ducros gave some formule to 
‘xpress the expense of water on the passage of ats boat, = 
er in ascending or descending through any n 
joining locks ; General Audekegey, author of the he History of 
