Tides in the North American Lakes. 25 
' The tabular diagram C, is intended to illustrate the observa- 
tions embodied in table B, referred to a system of rectangular 
ordinates. re ¥ 
The scale comprehends 40 parts in altitude to 1 inch, or 1 part 
=,'; inch; and 4 parts or 4 hours in longitude to linch, or 1 
hour=4 inch. As the observations. are referred to a superior 
plane, as zero, the proper algebraical sign would be minus ;. bit 
I have used the sign minus to represent depression, and plus ele- 
vation, indicating the relation in which they succeed each other. 
_ Example 1—Sept. 29th, at 2 o’clock, P. M. 28 inches, wind 
8. W. high, and at 9 o’clock, P.M. 314 inches, wind 8. mid- 
dling, = —34 inches, time 7 hours. . 
~ Sept. 30th, at 4 o'clock, A. M. 25 inches, wind S. high, = +63 
inches, time 7 hours; at 64 o’clock, A. M. 30 inches, wind S. W. 
high, =-—5 inches, time 23 hours; at 12 M. 21 inches, wind 
N. E. high, =+-9 inches, time 54 hours. 
' Result, 2 elevations, 154 inches, and 2 depressions of 84 inch- 
es, in 22 hours. 
Ex. IL—Oct. 2nd, 3 A. M. 33 inches, wind S. high; 6 A. M. 
25 inches, wind S. W. high, =+8 inches, time 3 hours. 
- At 11 A. M. 344 inches, wind N. W. high, = —94 inches, time 
5 hours; at 7 P. M. 25 inches, wind W. middling, = +9 inches, 
time 8 hours; at 10 P. M. 35} inches, wind S. W. middling, 
=~ 10 inches, time 3 hours. 
Result, 2 elevations +-8+9=17 inches, and 2 depressions = 94 
—10=~— 194 inches, in 19 hours. 
Ex. Il.—Oct. Ath, 1 A. M. 13 inches, wind N. high, and at 6 
A.M. 30 inches, wind N. high, = —17 inches, time 5 hours. 
At 113 A.M. 0 in., wind N. strong, =+30 inches, time 54 
hours; at 5 P, M. 32 inches, = —32 inches, wind N. W.- high, 
time 54 hours; and at 11 P.M. 14 inches, wind N. W. high, 
=-+14 inches, time 6 hours. 
Result, 2 elevations +30+14=44 inches, and 2 depressions 
~17 -32= ~ 49 inches, time 22 hours. 
‘tis believed that these examples illustrate the principles in- 
volved, in such a manner as to induce continued and minute in- 
vestigation, and the employment of instruments to comprehend 
lof the elements entering into the calculation. 
_ Colonel Whiting remarks, that “in speculating on the supposed 
tides of the North American lakes, it has been natural to regard 
Vol. xxv, No. 1,—April-June, 1843. 4 
