A mark is placed upon the projecting tube at the lower end of the percolator, and the tube at this point may be drawn out sufficiently to decrease the width of meniscus to one-eighth inch. Into the percolator is first introduced a small disk of wire gauze or perforated porcelain, with heavy wire pendant in the tube. Through the rubber stopper a small glass tube is passed and its lower end pressed firmly upon the wire or porcelain disk, its upper end being curved and supplied with a pinch-cock. Into the percolator is now poured one inch of fine shot (No. 20) and then one inch of fine sand which has been previously digested with hydrochloric acid and well cleaned of dust by washing. _The zero._—After the shot and sand have been shaken even, the burette is filled with water and raised above the level of the sand, wetting the percolator for four inches of its length. The burette is lowered and the shot and sand bed allowed to drain by opening the pinch-cock of the inner tube. The burette is raised and the shot-sand flooded repeatedly until, by lowering the burette until the zero mark of the percolator tube is reached, a uniform reading on the burette is secured. Thus the shot-sand bed is completely charged with water. The water level is now made zero on the percolator stem, the burette filled to its zero mark and the apparatus is prepared for introduction of the soil. _The Determination._—From 100 to 200 grams of soil, previously dried free of moisture, are weighed, the burette raised until the water level is three inches above the sand, and the soil gently dropped through a funnel into the water. When the soil has been introduced and wetted completely the water level is raised above the soil and allowed to remain thus two hours. The burette is then lowered and the water allowed to drain from the wetted soil. Four to six hours are usually given the draining, the reading taken on the burette after establishing the zero on the percolator stem, the volume of absorbed water thus ascertained and divided by the weight of soil multiplied by 100; the result expresses the water absorbed per hundred of soil. Example: Water required to saturate disk, etc. 0.50 cubic centimeter. Weight of air-dried soil taken 20.00 grams. Moisture at 105° therein 14.25 per cent. Weight water in soil 2.85 grams. Reading of burette after saturation 10.75 cubic centimeters. Less water required for disk, etc 9.25 „ „ Temperature 20°.00 Weight of 9.25 cubic centimeters H₂O at 20° 9.22 grams. Total weight of water retained by soil 12.07 „ Per cent water retained by soil 60.35 per cent. For general analytical work the correction for variations in the weight of water for different temperatures is of no practical importance.