Grams. Weight of pyknometer 13.4789 „ „ pyknometer full of distilled water at 20° 62.8934 „ „ water in pyknometer 49.4145 „ „ dry soil taken 10.0000 „ „ pyknometer + dry soil + filled with water at 20° 67.9834 „ „ soil and water 54.5045 „ „ water 44.5045 „ „ water displaced by ten grams soil 4.9100 Then specific gravity = 10.000 ÷ 4.9100 = 2.04. =98. Specific Gravity of Undried Soils.=—It is often desirable to determine the specific gravity of an undried portion of the soil. For this purpose a portion of the sample is dried at 100° to determine its percentage of moisture. The specific gravity is then determined on a ten gram sample of the undried soil as just given. The actual weight of soil taken is calculated from the percentage of moisture obtained in the first instance. In the case given if the percentage of moisture at 100° be ten then the actual weight of dry soil taken is nine grams. This number is therefore used in making the calculations. In all statements of specific gravity taken in the manner described the temperature at which the pyknometer is calibrated should be stated and all weighings where water is involved made at that degree. =99. Volume of Soil.=—If it be desired to calculate the volume occupied by a soil it is easily done by dividing the weight of water displaced by the weight of one cubic centimeter of water of the temperature at which the determination took place. In the case given one cubic centimeter of water at 20° weighs 0.998259. Then 4.9100 ÷ 0.998259 = 4.9186 cubic centimeters = volume occupied by ten grams of dry soil excluding interstitial spaces between particles. =100. Volumetric Methods.=—The water displaced by a given weight of soil may also be measured volumetrically by the method of Knop.[72] Place 200 grams of the soil in a flask of from three to five hundred cubic centimeters capacity. Add a measured quantity of water, and shake thoroughly to eliminate air, and fill up to the mark from a burette. The quantity of water required to complete the volume subtracted from the number expressing the volume of the flask will give the volume of water displaced by the earth.