A NEW EVAPORATION FORMULA 
41 
17. The other two values in parentheses in that column were computed in the 
same manner. 
The change in barometric correction from day to day, shown in the second 
column of Table 17, was computed by equation (15), and is illustrated in Table 18. 
In this table the values in columns 2 to 9 inclusive which are not enclosed in paren- 
theses are the values of b„ , b wi , . . . b„, as defined on page 21, and as computed 
from the pressure differences shown in Table 15. The values in parentheses at the 
heads of these columns are the constants of equation (15). These should be con- 
sidered as repeated down the column. The sum of the products of the constants 
into the values of b„ , 6«i, K, ....... b nt gives the change in barometric correc- 
Table 17 — Example of compulation of daily barometric correction, Harbor Beach 
Date 
Barometric correction 
Elevation of water surface 
Change in 
correction 
Based directly on 
computed values 
To conform 
to values 
computed by 
step (1) 
Final 
Observed 
Corrected 
for 
barometric 
effect 
1910 
Aug. 26 
Ut.) 
(ft.) 
(-0.124) 
+ .026 
+ .024 
+ .067 
+ .196 
+ .015 
- .012 
+ .080 
+ .029 
+ .048 
+ .121 (+0.095) 
+ .040 
- .016 
+ .083 
- .101 
+ .039 
+ .129 
- .006 
+ .056 
- .041 
- .004 (+ .006) 
(ft.) 
0.000 
- .003 
- .005 
- .008 
- .010 
- .013 
- .016 
- .018 
- .021 
- .023 
.000 
+ .001 
+ .002 
+ .003 
+ .004 
+ .005 
+ .006 
+ .007 
+ .008 
+ .009 
.000 
(ft.) 
- 0.12 
+ .02 
+ .02 
+ .06 
+ .19 
.00 
- .03 
+ .06 
+ .01 
+ .02 
+ .10 
+ .04 
- .01 
+ .09 
- .10 
+ .04 
+ -14 
.00 
- .05 
- .03 
+ .01 
579+/*. 
579+//. 
27 
+0.150 
- .002 
+ .043 
+ .129 
- .181 
- .027 
+ .092 
- .051 
+ .019 
+ .073 
- .055 
- .056 
+ .099 
- .184 
+ .140 
+ .090 
- .135 
- .050 
+ .015 
+ .037 
28 
29 
30 
31 
Sept. 1 
2 
1.24 
1.19 
1.26 
1.15 
1.17 
1.30 
1.20 
1.28 
1.25 
1.21 
3 
4 
5 
6 
7 
8 
1.34 
1.55 
1.34 
1.27 
1.30 
1.34 
1.31 
1.27 
1.43 
1.45 
1.38 
1.41 
1.30 
1.29 
1.28 
1.28 
9 
10 
11 
12 
13 
14 
15 
tion from the preceding to the current day shown in the last column of Table 18. 
Thus +0.150 foot is the change in the barometric correction from August 26 to 
August 27, 1910. This means that to the observed rise in the water surface at that 
gage between the dates stated, one must add 0.150 foot to get the true rise in the 
mean surface of the whole lake, in so far as it can be determined from readings on 
this gage alone, and corrected for only barometric effects. 
In the preceding paragraph there has been illustrated step (2), page 22. 
Referring to Table 17, step (3) consists in applying, one by one, the change in 
barometric correction from day to day shown in column 2, to the computed cor- 
rection for the selected day, shown in parentheses in column 3. This gives the 
values in column 3 not in parentheses. Thus, beginning with the first selected day 
shown, August 26, the values +0.150, —0.002, . . . are applied successively to 
(—0.124), obtaining +0.026, +0.024 .... At the second selected day, Septem- 
