148 
Journal of Agricultural Research 
Vol. XI, No. 4 
ure absorbed at x° C., x being the temperature at which the absorption 
boxes had been exposed. The conception of making such a determina¬ 
tion did not originate with Hilgard, but with Schiibler as early as 1830. 
The method (27, p. 80) of the latter, however, did not insure the absorp¬ 
tion of the maximum amount of moisture, too thick a layer of soil being 
exposed. Hilgard’s method is a refinement of that of Schiibler, provid¬ 
ing for a higher humidity of the atmosphere, a shallower layer of soil, 
thus permitting a more rapid saturation, and lastly the avoidance of 
fluctuations in temperature, which cause a precipitation of dew upon 
the soil. 
The hygroscopic coefficient of soils has been but rarely determined 
during the past 40 years, although during the previous four or five 
decades it had received considerable recognition. In the early days of 
soil investigation undue importance was attached to the relative absorb¬ 
ent powers of soils with respect to atmospheric moisture, it being sup¬ 
posed that it served to some extent as an index of fertility. Thus, 
Davy (9, p. 184) states: 
I have compared the absorbent power of many soils with respect to atmospheric 
moisture, and I have always found it greatest in the most fertile soils: so that it affords 
one method of judging of the productiveness of land. 
He also considered that in the case of soils with a high hygroscopic 
coefficient plants were supplied with moisture in periods of drouth, the 
hygroscopic power of the soil enabling it to render the water of the atmos¬ 
phere available to the plants (9, p. 183). Schiibler accepted the second 
of Davy's views but not the first, mentioning (27, p. 82) that he had 
found that a 
pure, infertile clay absorbs in 12 hours . . . more than the very fertile garden 
soil.—Translation. 
Liebig (17. p. 48) also accepted Davy's view as to the value of the moist¬ 
ure absorbed from the air, and it continued to be indorsed by the fore¬ 
most investigators until 1875, when the work of Sachs, Wilhelm, Reisler, 
Heinrich, and Mayer finally proved the falsity of it. The reaction from 
the old view carried to the opposite extreme, and it became almost 
universally accepted that a knowledge of the hygroscopic power of 
different soils is practically valueless. Apparently the question of the 
usefulness of a knowledge of the relative hygroscopicity of a soil was 
confused with the distinct question of the usefulness to plants of the 
hygroscopic moisture. Mayer appears largely responsible for this con¬ 
fusion. In 1871 (21, p. 130) he fully indorsed the older view: 
The absorptive power of the soil for water ... is under all circumstances a useful 
soil property , as it becomes active only when there is an actual scarcity of water in the 
soil and so acts as a regulator . . . The water thus condensed in porous solid bodies 
conducts itself exactly like other capillary held water and can, for example, when a 
field soil has in this way condensed water, be taken up by a plant’s roots just like that 
