M. Girard on Navigable Canals. 117 
as a basis for the distribution of the lifts of any number of 
paren locks on a canal. 
Since the expense of water, from any basin, necessary for 
a double passage of boats in the lock which joins that basin, 
is always proportionate to the lift of the lock, when, accord- 
ing to the supposition generally adopted, the draft of water 
of the ascending boat is equal to that of the boat which de- 
scends, it is evident that, if we continue the same su posi- 
tion, the reciprocal condition of a proper distribution of the 
locks consists in adapting their lifts to the quantity of water 
that the adjoining reservoir destined to supply water, can 
furnish without i inconvenience, 
This principle established, let us admit that the highest 
lock of a canal i is CO constructed i in fase to it, itis clear 
_ aaee sone BF v 
oa sae oars Sie Sa: ae ert ped " Cle ome 
its locks should have < same dimensions as the first ; ; ie 
then the water drawn from the first level, would pass to the 
second, thence to the third, and soon ‘successively to the 
last and lowest. 
In case of a negative expenilinare; the same volume of 
‘water would ascend through all the locks in } succession; from 
pd ax ce atince st level.* _ 
moe length of orth the canal, would onl itive or 
negative expense of water necessary for eres 
ofitinse boats through any one of the locks. 
_ But the above supposition does not hold good in practice. 
ees level of a canal lose oses, Jaonnsain. én a certain 
level. el. The positive : 
when caused by th desea a oa, at e | er one when caused by 
asalready prari-oary 
Po into an erroneous pes 
