ST. ALBANS AND ITS NEIGHBOURHOOD. 
217 
except that which is evaporated or absorbed by vegetation, 
sinking into it and partialty saturating it down to the under¬ 
lying impermeable G-ault. Rivers on the Chalk are therefore 
not usually fed by surface-water as are those on impermeable 
Rainfall, Percolation, and Evaporation at Rothamsted 
for the 39 Years April 1871, to March, 1910. 
Year. 
Kainfall. 
Percolation. 
Evaporation. 
Summer. 
Winter. 
Year. 
Summer. 
Winter. 
Year. 
Summer. 
Winter. 
Year. 
1871-72 
17*22 
11 *52 
28-74 
3*25 
5*60 
8-85 
13*97 
5*92 
19*89 
72-73 
I 4 'I 3 
19-99 
34*12 
i *57 
11-64 
I 3 - 2 I 
12-56 
8*35 
20*91 
73-74 
n-68 
9*83 
21-51 
•58 
3 *i 6 
3*74 
ii-io 
6-67 
17-77 
74-75 
13-10 
13-40 
26-50 
•79 
6-21 
7-00 
12-31 
7-19 
19-50 
75-76 
17*39 
1928 
36-67 
4*59 
12-97 
17*56 
12-80 
6-31 
I 9 -II 
76-77 
14*92 
21-36 
36-28 
3*82 
15*31 
19-13 
ii-io 
6-05 
17*15 
77-78 
14*43 
13-92 
28*35 
3*06 
8*75 
11 *81 
ii *37 
5 *i 7 
16-54 
78-79 
18-66 
16-97 
35*63 
5*99 
13*25 
19-24 
12-67 
3*72 
16-39 
79-80 
25*75 
7*03 
32-78 
11-94 
5-82 
15*76 
13*81 
3*21 
17*02 
1880-81 
17-06 
19-32 
36*38 
5*54 
i 5 *i 5 
20-69 
11-52 
4-17 
15-69 
81-82 
13-76 
16-06 
29-82 
3*03 
10*20 
13*23 
10-73 
5*86 
16-59 
82-83 
16*37 
21-77 
38-14 
3*82 
17*09 
20-91 
12-55 
4*68 
17*23 
83-84 
14-64 
12-81 
27*45 
3*55 
8-41 
11-96 
11*09 
4 * 4 ° 
15*49 
84-85 
ii*i 5 
14-11 
25-26 
2*59 
9*58 
12-17 
8-56 
4*53 
13-09 
85-86 
14*88 
i 5*56 
30*44 
4*54 
12*57 
17-11 
10-34 
2*99 
13*33 
86-87 
12-58 
1602 
28-60 
2-76 
11*00 
13-76 
9-82 
5*02 
14-84 
87-88 
9 *i 9 
n-86 
21-05 
•90 
9-02 
9-92 
8*29 
2-84 
n*i 3 
88-89 
16-56 
12-36 
28-92 
5*55 
8*io 
13*65 
II *OI 
4-26 
15-27 
89-90 
i 9' I 4 
12-83 
3 i *97 
6*77 
9-28 
16-05 
12-37 
3*55 
15-92 
1890-91 
13*36 
8-99 
22-35 
2-94 
5*8o 
8-74 
10-42 
3 *i 9 
13-61 
91-92 
14-61 
16-85 
31*46 
3*95 
i 3 * 5 o 
17*45 
io-66 
3*35 
14 01 
92-93 
13*90 
13*77 
27-67 
3*74 
9 37 
13-11 
10-16 
4*40 
14-56 
93-94 
8-99 
16-54 
25*53 
•06 
11-72 
11-78 
8-93 
4-82 
13*75 
94-95 
14-09 
14-94 
29*03 
3*05 
ii *75 
14-80 
11*04 
3 *i 9 
14-23 
95-96 
12-84 
15*45 
28-29 
3*92 
9*94 
13-86 
8*92 
5 * 5 i 
14*43 
96-97 
15*94 
19-09 
35*03 
6-69 
15*07 
21-76 
9*25 
4*02 
13-27 
97-98 
12-51 
8-47 
20-98 
2-24 
4*53 
6-77 
10-27 
3*94 
14-21 
98-99 
9-20 
14-61 
23-81 
1-07 
10-16 
11*23 
8-13 
4*45 
12-58 
99-1900 
n *94 
18-46 
30-40 
2-48 
15-28 
1776 
9*46 
3 *i 8 
12-64 
1900-01 
io-94 
13*87 
24-81 
i *59 
9*50 
11-09 
9*35 
4-37 
13-72 
01-02 
io -95 
10-78 
21-73 
2-56 
6-73 
9*29 
8-39 
4*05 
12-44 
02-03 
12-18 
12-30 
24-48 
2-90 
7*63 
IO *53 
9-28 
4*67 
13*95 
03-04 
20-67 
19-47 
40-14 
10-52 
16-29 
26-81 
10-15 
3 *i 8 
13*33 
04-05 
io-88 
11*38 
22-26 
i*3o 
6-84 
8*14 
9*58 
4*54 
14-12 
05-06 
11-95 
14-06 
26-01 
4*05 
9 * 5 i 
13*56 
7*90 
4*55 
12*45 
06-07 
8*59 
16-34 
24*93 
i *75 
11-00 
12-75 
6-84 
5*34 
12" l8 
07-08 
12-64 
17*04 
29-68 
1-48 
11-70 
13-18 
1 i-i6 
5*34 
16-50 
08-09 
13*85 
10-29 
24-14 
4-01 
6-78 
1079 
9-84 
3 * 5 i 
13*35 
09-10 
15-01 
17*05 
32-06 
3*84 
13*34 
17-18 
ii*i7 
3 * 7 i 
1488 
Mean 
14-04 
14-76 
H 
28-80 
3*56 
10-19 
13*75 
10-48 
4*57 
15*05 
formations, but by springs which rise in their beds. The 
presence of a spring indicates that the Chalk is saturated up 
to at least a little above the spring; were it not saturated up to 
the bed of the river, water would sink out of the river into the 
