As Hilgard has pointed out, if a soil can be practically freed from alkali by underdrainage connected with a thorough saturation by irrigation, it may be centuries before the alkali will accumulate in that soil again when ordinary irrigation only is practiced. It may thus become possible to reclaim large extents of alkaline soil little by little by treating them with an excess of irrigation water in connection with thorough underdrainage. The composition of the alkali on the surface of the soil due to the causes above set forth is thoroughly illustrated by the analyses of Hilgard and Weber, which follow: TABLE SHOWING COMPOSITION OF ALKALI SALTS IN SAN JOAQUIN VALLEY. ═════════════╤════════════════════════════════════════════ │ FRESNO COUNTY. ─────────────┼──────────────────────────────────────────── │ Sections 13 and 24 T. 14 S. R. 19 E., 4 │ miles S. W. from Fresno. │ ─────────────┼────────┬─────────────────────────────────── │ Alkali │ Alkali Spot, 1889. │ soil, │ │ 1888. │ ─────────────┼────────┼────────┬────────┬────────┬──────── │ „ │ 1 inch │ 18 │ 26 │ 42 │ │surface.│ inches │ inches │ inches │ │ │ bel. │ bel. │hardpan. │ │ │surface.│surface.│ ─────────────┼────────┼────────┼────────┼────────┼──────── Soluble salts│ │ 0.76 │ 0.20 │ 0.18 │ 0.16 in 100 │ │ │ │ │ parts soil │ │ │ │ │ Potassium │ │ │ │ │ sulfate │ │ │ │ │ [D]Potassium │ │ │ │ │ nitrate │ │ │ │ │ Potassium │ │ │ │ │ carbonate │ │ │ │ │ (Saleratus)│ │ │ │ │ Sodium │ large │ small │ small │ very │ very sulfate │ │ │ │ slight │ slight (Glauber’s │ │ │ │ │ salt) │ │ │ │ │ Sodium │ very │ large │ small │ large │ large carbonate │ slight │ │ │ │ (Sal-soda) │ │ │ │ │ Sodium │chiefly │moderate│chiefly │moderate│moderate chlorid │ │ │ │ │ (Common │ │ │ │ │ salt) │ │ │ │ │ [D]Sodium │ │ │ │ │ phosphate │ │ │ │ │ Calcium │moderate│ small │ very │ very │ very sulfate │ │ │ slight │ slight │ slight (Gypsum) │ │ │ │ │ Magnesium │ │ │ │ │ sulfate │ │ │ │ │