. 
=. 
294 M. P. S. Girard on Navigable Canais. 
Bu ee | SR 
“++ Tipsy )=h-2+e( B73) ; 
making; this height equal to the draft of water ¢,, or ¢, of the 
boats which ascend and descend, or 
B n 
h—x+ (gy) ah, « 
we shall have 
and therefore 
n=log. (t,+x—h) 
oH 
B 
B+S. 
This is the number of double passages after which the 
height of water in the level B_wili have become precisely 
equal to the draft of water of the boats, and_ will therefore 
cease to be navigable, if it has received no new supply © 
log. 
Let #’, 
the levels B, B, B,,, B,, &c. by the descent of the first boat 
through all the locks ; 
uu, w",,, wy &e, the increased height of the same 
levels by the descent of the second boat; he 
ua", ww", &e., the increase by the descent oft 
third, &c. 4 
So that the upper index will designate the numerical vd 
der of the boat in the series, and the lower one the ra? h 
the lock in the canal, counting from the summit level; ¢2¢ 
of thes: quantities 
