================================+============+=========+======== | “ROTTEN | SUBSOIL | SOIL |LIMESTONE.” |(YELLOW).|(BLACK). --------------------------------+------------+---------+-------- FINE EARTH. |Depth 12 ft.| 2-3 ft. |15 ins. Chemical analysis of fine earth.| | | --------------------------------+------------+---------+-------- Insoluble matter | 10.90 | 71.54 | 78.29 Soluble silica | | | Potash (K₂O) | .25 | .54 | .33 Soda (Na₂O) | .32 | .23 | .08 Lime (CaO) | 45.79 | 1.08 | 1.37 Magnesia (MgO) | .88 | .77 | .36 Br. Ox., of Manganese (Mn₃O₄) | | .05 | .14 Peroxide of Iron (FeO) | 1.42 | 5.42 | } Alumina (Al₂O₃) | 1.96 | 13.15 | } 14.22 Phosphoric Acid (P₂O₅) | | .05 | .10 Sulfuric Acid (SO₃) | | .04 | .03 Carbonic Acid (CO₂) | 35.73 | | Water and Organic matter | 2.84 | 6.99 | 5.75 | ------ | ----- | ------ Total | 100.09 | 99.86 | 100.67 | | | Humus | | | 1.93 “ Ash | | | 4.38 Hygroscopic moisture | | 10.35 | 12.82 absorbed at °C | | 19° | 19° --------------------------------+------------+---------+-------- It appears from the above table that in the change from the original limestone to the soil mass as found at three feet depth, 81.5% of the lime carbonate has been eliminated by leaching, leaving behind somewhat less than one fifth of the original mass. Taking the average depth of the soil mass at 8 feet, this thickness of material has required about 45 feet of the rotten limestone. Considering that notwithstanding the tenacity of the clay soil, some of it must in the course of time have been washed away, we may safely assume that the original rock surface was from 50 to 60 feet higher than at present.