=219. Taking Samples of Soil in Sterilized Tubes.=—Brass tubes are prepared twenty centimeters in length and one and a half in diameter. One end is ground to a beveled edge and compressed in a mold so as to make the cutting edge slightly smaller in diameter than the internal diameter of the tube. It is then ground or filed until smooth and sharp. The blunt end of the tube is stoppered loosely with cotton and it is then sterilized by heating for an hour to 150°. Rubber caps are provided and each one has placed at the bottom a rubber ball to prevent the rubber from being cut by the edges of the brass tube. The caps should be of two distinct colors. Half of the rubber caps are sterilized by being boiled for an hour in water for three successive days. The caps cannot be heated to 150° dry heat with safety. On removing the brass tube from the sterilizing oven as soon as it is cool enough to handle, a sterilized rubber cap is slipped over its cutting end. An unsterilized cap is then slipped over the other end containing the cotton plug. Inasmuch as the cotton plug is never removed it is not necessary to sterilize the cap covering it. Large numbers of the tubes can thus be prepared for use and they can be safely transmitted to a distance by express or mail. For convenience, each tube is encased in a small cloth bag, which is tied with a cord carrying a tag on which the necessary data can be recorded at the time of taking the sample. The tubes and their rubber caps thus carefully sterilized should not be removed from their cloth envelopes until the moment of taking each sample. After the sample has been taken and the cap replaced on the tube the latter should be immediately enclosed in the cloth sack and labeled with one of the tags therewith enclosed. The sample should be taken in two kinds of soil, in one instance in a cultivated soil, which is most characteristic of the locality, and in the second place a virgin soil of the same type. The virgin soil may be either soil which has been covered with grass or in forest. The spots at which the samples are to be taken having been previously selected, the tags for each tube should be prepared beforehand so as to avoid delay at the time of sampling. A pit with straight walls should be dug, the sides of which are at least two feet wide and even three feet would be better. The pit should be about forty-two inches deep. One of the sides having been made perfectly smooth and without allowing the loose fragments from the top to fall down and adhere to the walls below, the spots at which the samples are to be taken should be marked with a tape line at the following points; _viz._, three, fifteen, twenty-seven, and thirty-nine inches, respectively, below the surface. Beginning at the bottom point, carefully scrape off the surface of the wall over an area slightly larger than that of the end of the sample tube by means of a spatula, which, just previous to use, has been held for a moment