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. 
The scale comprehends 40 parts in altitude to 1 inch, or 1 part 
=,/; inch; and 4 parts or 4 hours. in longitude to l inch, or 1 
hour=4 inch. As the observations are referred to a superior 
plane, as zero, the proper algebraical sign would be minus ; but 
I have used the sign minus to represent depression, and plus ele- 
vation, indicating the relation in which they succeed each other. | 
Example L—Sept. 29th, at 2 o’clock, P. M. 28 inches, wind 
S. W. high, and at 9 o’clock, P. M. 314 inches, wind S. mid- 
dling, = —34 inches, time 7 hours. 
Sept. 30th, at 4o’clock, A. M. 25 inches, wind 8. high, = +63 
inches, time 7 hours; at 64 o’clock, A. M. 30 inches, wind 8. W. 
high, = —5 inches, time 24 hours; at 12 M. 21 inches, wind 
N. E. high, =+-9 inches, time 53 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. 353 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. U1.—Oct. 4th, 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. Oin., wind N. strong, =+30 inches, time 53 
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= —A9 inches, time 22 hours. 
It is 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 
all of 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. xty, No. 1.—April-June, 1843. 4 
