8 
Research Bulletin No. 3 
REVIEW OF PREVIOUS WORK. 
OLDER VIEW OF THE IMPORTANCE OF THE HYGROSCOPICITY OF SOILS. 
Davy considered that the hygroscopic power of soils enabled 
them to render the water of the atmosphere available to plants 
and that the relative hygrosopicity of a soil served as an index 
of the productiveness of land. "The power of soils to absorb 
water from air is much connected with fertility. When this 
power is great the plant is supplied with moisture in dry seasons, 
and the effect of evaporation in the day is counteracted by the 
absorption of aqueous vapor from the atmosphere, by the interior 
parts of the soil during the day, and by both the exterior and 
interior during the night." 1 "I have compared the absorbent 
power of many soils with respect to atmospheric moisture, and 
T have always found it greatest in the most fertile soils so that it 
affords one method of judging of the productiveness of land." 2 
Schubler. 3 who was the first to determine the maximum 
amount of moisture absorbed by various soils when exposed to 
an atmosphere almost saturated with water vapor, agreed in the 
main with Davy's view but pointed out that the power of absorp- 
tion, considered alone, might be very deceptive as he had found 
that "a pure, infertile clay absorbs in twelve hours * * * 
more than a very fertile garden soil." 
Liebig 4 accepted Davy's view as to the value of the moisture 
absorbed from the air. "When in the hot summer the surface of 
the ground is dry, and there is no replacement of moisture by 
capillary attraction from the deeper strata, the powerful attrac- 
tion of the soil for the vapors of water in the air provides the 
means for supporting vegetation." 
Sachs 5 in 1859 distinguished experimentally between the 
available and the nonavailable Avater. He grew tobacco plants in 
three different soils. — a vegetable mold, a loam, and a quartz 
sand — and found that they wilted permanently, while 12.3, 8.0, 
and 1.5 per cent respectively of water remained in the soil. The 
maximum water capacities of the three soils were 46, 52.1, and 
20.8 per cent. He made no determination of the relative hygro- 
scopicity of the soils. The considerations leading up to these 
experiments he stated 6 as follows: 
"If one wishes to learn to know the relation of the plant to 
1 Daw. Sir Humphrey. Agricultural Chemistry, Second Edition, 1814, 
p. 183. 
2 Ibid., p. 184. 
s Schiibler, G. Grundsatze der Asrikulturchemie, 1830, vol. 2, p. 82 
4 Liebig, J. Letters on Modern Agriculture, 1859, p. 48. 
5 Sachs, J. Leber den Einfluss der chemischen und physikalischen Be- 
schaffenheit des Bodens auf die Transpiration der Pflanzen. Landwirth- 
schaftlichen Versuchs-Stationen, 1859, vol. 1, p. 235. 
6 Ibid., p. 234. The writer is responsible for the translation. 
