88 BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 
light than now seems desirable, although not enough to develop ex- 
cessive temperatures. In contrast, there are also presented the re- 
sults of nine tests on coarse granitic gravels, from depths of 1 to 3 
feet, containing minimum amounts of humus and clay. The wilting 
coefficients were determined in the same manner as the other group, 
and at almost the same time. 
Table 2. 
Capillary moisture, moisture equivalent, and ivilting coefficient of 19 
soils. (Wilting coefficients determined synchronously.) 
Sample No. 
Capil- 
lary 
moist- 
ure 
(G). 
Moist- 
ure 
equiva- 
lent 
(100-G). 
Mean 
wilting 
coeffi- 
cient 
(spruce 
and 
fir).i 
Humus 
by ig- 
nition. 
Clay. 
Water 2 
soluble 
matter. 
Ratio mean 
wilting coeffi- 
cient. 
To 
capil- 
larity 
To 
mois- 
ture 
equiva- 
lent. 
Ratio final 
' wilting coeffi 
cient. 
Final * j 
wilting j 
coeffi- ' 
cient. 1 To 
capil- 
larity. 
To 
mois- 
ture 
equiva- 
lent. 
539. 
555. 
534. 
547. 
545. 
549. 
544. 
526. 
546. 
538. 
Per 
cent. 
17.07 
20.29 
24.06 
29.34 
33.77 
36.16 
41.56 
49.92 
60.00 
89.05 
Per 
cent. 
11.68 
11.72 
14.45 
20.32 
22.02 
19.95 
26.30 
29.84 
42.72 
73.50 
Per 
cent. 
3.17 
3.00 
3.90 
6.01 
6.02 
7.04 
8.68 
8.60 
20.46 
21.71 
Per 
cent. 
3.29 
3.52 
3.00 
6.56 
7.09 
6.04 
11.64 
9.75 
21. 10 
27. 00| 
Per 
cent. 
4.5 
0.4 
2.2 
6.7 
3.6 
4.2 
Parts 
per 
million. 
305 
275 
465 
270 
845 
555 
1,030 
530 
200 
1,250 
0. 
.148 
.162 
.205 
.178 
.195 
.209 
.172 
.341 
.244 
0.271 
.256 
.270 
.295 
.273 
.353 
.330 
.288 
.479 
.295 
Group averages, granitic loams. 
.204 
,311 
Per 
cent. 
2.56 
2.52 
3.301 
5.261 
5. 18 
6.101 
7.831 
6. 95] 
11. 171 
13. 89 1 
0.150 
.124 
.137 
.179 
.153 
.169 
.188 
.139 
.186 
.156 
0.219 
.215 
.228 
.259 
.235 
.306 
.298 
.233 
.262 
1 58 
244 
292. 
37.. 
235. 
36.. 
11.02 
5.04 
2.73 
1.02 
1.5 
11.46 
3.53 
2.00 
1.33 
0.2 
12.00 
5.06 
3.09 
2.09 
3.1 
12.95 
4.35 
2.47 
1.74 
2.7 
12.96 
5.62 
2.93 
1.79 
1.5 
13. 18 
4.86 
2.27 
1.85 
1.9 
13.61 
5.19 
2.76 
1.76 
2.5 
15.30 
5.57 
2.54 
1.92 
2.1 
15.65 
5.03 
2.54 
1.31 
3.7 
Group averages, granitic gravels . 
Grand averages 
Mean variation of single values. . 
Percentage of mean variation 
Probable error in average 
,248 
.174 
,257 
.191 
.226 
.172 
.203 
.166 
.162 
,542 
,567 
,611 
,568 
,521 
.467 
,532 
,456 
.506 
.200 
.202 
.0333 
16.5 
.0066 
.530 
.415 
.1157 
35.9 
.0230 
1.79 
1. 18| 
2.25! 
1.641 
2.06! 
1.85! 
1.76 
1.62| 
1.621 
.162 
.103 
.188 
.127 
. 159 
.140 
.129 
.106 
.104 
355 
334 
445 
377 
367 
381 
339 
291 
322 
.135 
.147 
. 0228 
15.5 
.0045 
.357 
.298 
.0607 
20.4 
.0121 
1 In these tests spruce and fir gave almost the same figures, on the average. 
2 200 grams soil leached on filter, with 1 liter water, through 24-hour period. For the gravel group re 
suits are approximations, on account of lack of sensitive scale. 
3 Average of the moistures existing fcr last tree of each species. 
To avoid duplication of tables later there are also inserted here 
the moisture equivalents of the same soils. 
The comparison of capillary moisture and wilting coefficients 
given in Table 2 brings out the following facts : 
1. An examination of the column headed " Ratio of mean wilting 
coefficient to capillarity " shows that there is considerable variation 
in the individual results. In the first group the two results which 
are appreciably higher than the average are those for samples of the 
highest capillarity, resulting from unusual quantities of humus. 
