The table below indicates the effect of the three substances mentioned in increasing moisture absorption as compared with a very sandy soil from the pine woods of Mississippi, and a gray silt or “dust” soil from Washington, very fine-grained but poor both in humus and ferric hydrate. (For details of the physical composition of the Mississippi soils see table in chapt. 6, p. 93). A highly ferruginous soil from Oahu shows plainly the effect of that substance. TABLE SHOWING INFLUENCE OF SILT, SAND, CLAY, FERRIC HYDRATE, AND HUMUS ON MOISTURE ABSORPTION. ================================+======+======+=====+========= | 248 | 79 | 238 | 230 | | | | |Miss. |Wash’n|Miss.| Miss. |Pine | Dust |White|Flatwoods |Hills | Soil.|Pipe | Clay |Sandy | |Clay.| Soil. |Loam. | | | | | | | | % | % | % | % --------------------------------+------+------+-----+--------- Hygr. Moisture | 2.48| 4.92| 9.09| 9.33 Clay | 2.94| 1.27|74.65| 25.48 Ferric Hydrate | 1.64| | .15| Humus | .55| .44| 0.00| .50 Finest Silts (.01-.0250 mm.) | 60.10| 45.04|23.15| 68.60 Sands, f. and c. (.0250-.50 mm.)| 31.20| 42.40| .20| 4.70 --------------------------------+------+------+-----+--------- ================================+===========+===========+=====+===== | 246 | | 220 | 215 | | | | | Misc. | Oahu |Miss.|Miss. |Ferruginous|Ferruginous|Marsh|Marsh | Clay | Laterite. |Muck.|Soil. | Soil. | | | | | | | | | | | | % | % | % | % --------------------------------+-----------+-----------+-----+----- Hygr. Moisture | 18.60 | 19.66 |21.00|15.40 Clay | 28.15 | ? | Tr. | Tr. Ferric Hydrate | 12.10 | 41.00 | | Humus | little | 3.33 |66.10|19.83 Finest Silts (.01-.0250 mm.) | 40.33 | } 45.66 |33.94| 8.70 Sands, f. and c. (.0250-.50 mm.)| 15.61 | } | |70.18