I 357 I 
CASE II. 
But if at any inftant of time, whilft the wind was 
blowing, it was obferved, that when the water flood at e, 
the top of the tube out of which it is forced, it was de- 
preiTed in the other tube to fome given level bf, the al- 
titude at which it would have flood in each, had it im- - 
mediately fubfided, may be found in the following man- - 
ner ; 
Let /^=AB or EF. Then it is evident, that the column i 
DB is equal to the difference of the columns ef, gf. But - 
the difference of thefe columns is as d^b-d^x. Therefore . 
d^h 
c'x-d''b~d'-x% and confequently, x--^-^: 
For the cafes when the wind blows in at the narrow 
leg of the inflrument. 
Let EG or ad=^, gf = db=a’, and the dia- - 
meters eh, ca, refpedlively -d^ c, as before. Then it is 
evident, that the column ad is to the column gf as 
to d"'x» But thefe columns are equal. Therefore,, 
and confequently, x.:^-j,' This anfwers to 
CASE I. 
It is alfo evident, that the column ad is equal to the ; 
difference of the columns ab, db. But the difference of 
thefe columns is as bd^~rx. Therefore, d^x~bc"'-€-x, . 
Whence we get x~-J^.^' This correfponds to case ii. 
' ; As there is always a calculation to be macle for every ’ 
i ‘ 6 expe— - 
