A NEW EVAPORATION FORMULA 
39 
maps at points 3, 4, 5 and 6, at 8 a. m. and 8 p. m., 75th meridian time by inter- 
polation between the isobars are shown in Table 15. la the last two columns of 
this table are shown the pressure differences, (3-6) and (4-5) in the units used in 
equations (10) to (12) and (14) to (16) inclusive, pages 20-21. 
Table 15— 
Barometric "pressures arm 
ml Lake Michigan-Huron 
Barometric pressure in inches of mercury at 
In units o 
f 0.01 inch 
point — 
Date 
Hour 
3 
4 
5 
6 
Diff. (4-5) 
DifT. (3-6) 
1910 
Aug. 24 
8 p.m. 
29.75 
29.68 
29.87 
29.81 
— 19 
— 6 
25 
8 a.m. 
29.69 
29.60 
29.80 
29 . 74 
— 20 
— 5 
25 
8 p.m. 
29.70 
30.01 
29.64 
30.00 
+ 37 
— 24 
20 
8 a.m. 
30.08 
30.21 
30.11 
30.23 
+ 10 
-15 
20 
8 p.m. 
8 a.m. 
8 p.m. 
8 a.m. 
8 p.m. 
8 a.m. 
8 p.m. 
8 a.m. 
8 p.m. 
8 a.m. 
30.02 
30.05 
30.10 
30.22 
30.25 
30.36 
30.30 
30.00 
29.90 
30.23 
30.11 
30.12 
30.08 
30.16 
30.18 
30.25 
30.12 
29.92 
29.98 
30.20 
30.15 
30.16 
30.13 
30.18 
30.21 
30.33 
30.30 
30.21 
29.99 
30.20 
30.21 
30.24 
30.14 
30.13 
30.10 
30.21 
30.12 
30.05 
30.01 
30.12 
- 4 
- 4 
- 5 
- 2 
- 3 
- 8 
-24 
-29 
- 1 

-19 
-19 
- 4 
+ 9 
+ 9 
+ 15 
+ 18 
- 5 
-11 
+ 11 
27 
27 
28 
28 
29 
29 
30 
30 
31 
31 
8 p.m. 
8 a.m. 
30.27 
30.32 
30.20 
30.30 
30.17 
30.19 
30.13 
30.20 
+ 3 
+ 11 
+ 2 
— 10 
-16 
+ 3 
+ 14 
+ 12 
+ 9 
+ 3 
- 4 
- 7 
Sept. 1 
1 
8 p.m. 
8 a.m. 
8 p.m. 
8 a.m. 
30.23 
30.19 
29.83 
29.70 
30.18 
30.13 
29.80 
29.76 
30.16 
30.23 
29.96 
29.73 
30.14 
30.10 
29.87 
29.77 
2 
2 
3 
3 
8 p.m. 
29.85 
29.82 
29.74 
29.80 
+ 8 
+ 5 
4 
8 a.m. 
29.90 
29.85 
29.95 
29.85 
-10 
+ 5 
4 
8 p.m. 
8 a.m. 
29.93 
29.92 
29.83 
29.77 
29.95 
29.91 
29.84 
29.77 
-12 
-14 
+ 9 
+ 15 
5 
5 
8 p.m. 
29.89 
29.78 
29.89 
29.80 
-11 
+ 9 

8 a.m. 
8 p.m. 
29.70 
29 . 93 
29.78 
30.03 
29.80 
29 . 90 
29.88 
30.04 
- 2 
+ 13 
-18 
-11 

7 
8 a.m. 
8 p.m. 
30.19 
30.02 
30.15 
30.04 
30.13 
30.18 
30.23 
30.10 
+ 2 
-14 
- 4 
-14 
7 
8 
8 a.m. 
8 p.m. 
8 a.m. 
8 p.m. 
29.90 
29.99 
30.20 
30.13 
29.94 
30.08 
30.28 
30.18 
30.11 
29.89 
30.03 
30.13 
30.09 
29.99 
30.21 
30.23 
-17 
+ 19 
+25 
+ 5 
-19 

- 1 
-10 
8 
9 
9 
10 
8 a.m. 
30.12 
30.18 
30.24 
30.26 
- 6 
-14 
10 
8 p.m. 
30.03 
29 . 99 
30.14 
30.09 
-15 
— 
11 
8 a.m. 
30.02 
30.02 
30.20 
30.12 
— 18 
-10 
11 
8 p.m. 
30.03 
29.95 
30.10 
29 . 99 
-15 
+ 4 
12 
8 a.m. 
30.21 
30.22 
30.12 
30.04 
+ 10 
+ 17 
12 
8 p.m. 
30.37 
30.34 
30.21 
30.22 
+ 13 
+ 15 
13 
8 a.m. 
30.45 
30.44 
30.34 
30 . 37 
+ 10 
+ 8 
13 
8 p.m. 
30.31 
30.36 
30.30 
30.32 
+ 6 
- 1 
14 
8 a.m. 
30.30 
30.40 
30.33 
30.41 
+ 7 
-11 
14 
8 p.m. 
30.28 
30.31 
30.29 
30.35 
+ 2 
- 7 
15 
8 a.m. 
30.30 
30.35 
30.36 
30.40 
- 1 
-10 
15 
8 p.m. 
30.21 
30.26 
30.34 
30.31 
- 8 
-10 
The computation of the hourly barometric effects for September 5, 1910, is 
shown in Table 16. The barometric pressures at 8 a. m. and 8 p. m. there shown in 
columns 2 to 5 inclusive are taken directly from Table 15. In columns 6 and 7, at 
8 a. m. and 8 p. m. are recorded the differences in pressure between the actual 
