Note 35 — GENERAL SUMMARY AND CONCLUSIONS.

Soil samples were taken from the plain about 3 kilometers north of Ghardaia from an area where the vegetation is relatively good (see p. 40). The surface of the soil at the place is slightly depressed. Soil samples from the depressed area and samples from portions of the plain adjacent to it were settled under water, with the result that the proportion of fine soil was found to be less in the depressed area. Samples of the soil from the lower area were placed in air-tight cans and the moisture content determined subsequently. The soil was found to contain 0.8 per cent water. Through the kindness of the Bureau of Soils, U. S. Department of Agriculture, the critical moisture-content of the same soil was determined, which was 5 per cent. The critical moisture-content of mesa soil, taken from the creosote-bush slope at the foot of Tumamoc Hill, Desert Laboratory, as determined by the Bureau of Soils, is 10.5 per cent, which forms an interesting comparison of nearly similar situations.