p^s gram of substance absorbs pa gram of the gas and 100 grams of substance would absorb (100 × pa)/(p^s) grams. The specific gravities of the gases employed are calculated from the tables given by Landolt and Börnstein in “Physical and Chemical Tables,” page 5. The specific gravity of the quartz sand employed was 2.639; of the quartz powder, 2.622; of the kaolin, 2.503; of the humus, 1.462; of the iron hydroxid, 3.728; and of the calcium carbonate, 2.678. One liter of ammonia, at a pressure of 760 millimeters of mercury and a temperature of 0°, weighs 0.7616 gram; one liter of carbon dioxid, 1.9781 grams; one liter of aqueous vapor, 0.8064 gram; and one liter of dried air, 1.2931 grams. At a pressure of 720 millimeters, and at 20° temperature, a liter of air saturated with aqueous vapor at 0° weighs 1.1383 grams; saturated at 8.6°, 1.1362 grams; saturated at 10°, 1.1358 grams; saturated at 14°, 1.1340 grams; saturated at 18.2°, 1.1330 grams; saturated at 20°, 1.1321 grams; saturated at 30°, 1.1313 grams. The general results of the experiments are as follows: ABSORPTION AT 0°. Aqueous vapor Ammonia. Carbon dioxid. from saturated air. Grams. Cubic Grams. Cubic Grams. Cubic cm.[H] cm.[H] cm.[H] 100 grams quartz 0.159 197 0.107 145 0.023 12 „ „ kaolin 2.558 3,172 0.721 947 0.329 166 „ „ humus 15.904 19,722 18.452 24,228 2.501 1,263 „ „ Fe₂(OH)₆ 15.512 19,236 4.004 5,275 6.975 3,526 „ „ CaCO₃ 0.224 278 0.256 320 0.028 14 Footnote H: Reduced to 0° and 760 millimeters pressure mercury. The foregoing methods will suffice to show the procedures to be followed in estimating the maximum amount of any common gas or vapor a given quantity of soil may be made to absorb. We pass next to consider the quantities of gases or vapor soils _in situ_ may hold. =284. Method of Boussingault and Lewey.=[184]—This method is the oldest and most simple procedure for estimating the nature of the gases held in a soil _in situ_. For the purpose of collecting the sample of gas from the soil a hole, thirty to forty centimeters in depth, is dug, and a tube placed in it in a vertical position, having on its lower extremity a bulb perforated with fine holes. The hole is filled and the earth closely packed around the tube which is left for twenty-four hours. At the end of that time the tube is slowly aspirated until a volume of gas approaching from five to ten liters is obtained. _Estimation of Carbon Dioxid._—The carbon dioxid in the sample of gas is estimated by allowing it to bubble through a solution of barium hydroxid.