102 M . Girard on Navigable Cunais. 
or the other, according as you wish to turn to the one side or 
the other. 
I have not thought it worth while to protract this article, 
already extended to a tedious length, by specifying the ma- 
ny little practical matters, which will occur, in the construc- 
tion of my engine ; such as the mode of supplying the pails 
with oil, of casing the cylinder, so as to exclude it from the 
water of the wheel, &c. 
It scarcely needs to be added, that I have secured this in- 
vention by patent. 
References to the figure, Pi. Ul. 
a—piston-rod. 
bb—cylinders. 
cecc—water-wheel. 
dd—adjacent parts of the boat. 
e & f{—parts of the centre piece. 
g—gudgeon of the cylinder. 
h—neck on which the water-wheel turns. 
i & k—beginning and end of the induction tube. 
I] & m—same of eduction tube. 
n—stationary part of the cocks. 
o—moveable part of the same. 
p—cross-piece attached to the piston-rod. 
q—gudgeon of same. 
rrrr—arms of water-wheel. 
ss—steps for rods playing through steps in cylinder. 
tttt-—rods. , 
uuu—steps. 
Arr. XL—Memoir on Navigable Canals, considered in re- 
lation to the rise and fall, and the distribution of their 
Locks: by M. P. S. Girarp. | 
[Translated from the French as published in the “ Annales de Chimie’’— 
July, 1820: by J. Doolittle. ] 
The expense of. water in a navigable canal, during a giv- 
en time, is composed : 
Ist. Of a certain volume of water, evaporated from the 
surface : 
