In figure 12, A, B and C show the general exterior and interior form of the instrument. The handle is hollow and made of iron gas pipe covered with leather. On the inside of this, in the middle, is fixed a wooden plug a, which leaves two compartments, one in each end for holding the brass plug bb,’ and the wicker lubricating wad cc.’ The stem of the auger a, is heavy and made of eight-sided steel and the under end is strengthened with a heavy casting fitting into the auger guide g g. The end of the auger I I′ is triangular and hardened. The auger guide g g, is made out of a single piece of drawn steel tubing. Above it is strengthened by a ring-shaped piece of iron or copper and its lower end is furnished with saw teeth as shown in K and is hardened. The fixing key e, is bent in the form of a hook and can be passed through the two holes o o, of the auger stem and through the one hole o′ in the strengthened part of the auger guide. It permits the auger guide to be fixed upon the auger stem in two different positions, higher and lower. On one end it is cut squarely across and on the other provided with a conical hole drilled into it. It fits on the one hand exactly in the auger guide and on the other loosely plays in the cavity of the handle at b, designed to hold it when not in use. The cap d′ is made of heavy sheet brass and is fastened upon the end of the handle at c c′ after the manner of a bayonet. The wicker cartridge is made of rolled and sewed wicker-work. At the upper end it is provided with a metallic button and before use it is saturated with paraffin oil. It fits on the one side firmly in the auger guide and on the other in the cavity, of the handle c where it is kept when not in use. The union h is made of a brass tube which below is closed with a piece of solid brass upon the inside of which a hole is bored. In this hole rests the end of the auger stem when the union is placed firmly upon the auger guide.

The auger is placed together as is shown in A B, the union h is taken off and it is driven with gentle blows, turning it back and forth, to the proper depth into the soil. After the key is loosened the auger is lifted high enough so that the second hole appears and then it is fixed in position by the key. Then the boring is continued, turning the auger to the right, by which the auger, eating its way with its saw teeth, presses deeper into the ground and withdraws the material for analysis. After the auger guide has been filled through any desired length, say five to ten centimeters with the sample of soil, the whole auger is drawn out of the soil, the key removed, the auger stem withdrawn from the auger guide, the apparatus opened by turning the bayonet fastening of the stopper on the handle, the brass plug placed in the end and then with the smooth part forward, from above, it is allowed to fall into the auger guide until it reaches the soil. The auger stem is then put back, the point of it fitting into the hole of the plug and the sample of soil shoved out of the auger guide. The auger guide is again fixed on the auger stem by the key and then the apparatus is ready for a second operation. When the borings cease the wicker cartridge is drawn out of the handle and shoved, the soft end forward, from above, into the auger guide and the brass plug after it and pushed through with the auger stem. By this process the wicker cartridge gives up a sufficient amount of paraffin oil to completely grease the inside of the auger guide and to protect it from rust. After use the instrument should be cleaned on the outside by means of a cloth, the plug and wicker wad replaced in their proper positions, the cap fixed on the handle and the union on the point of the instrument.

The length of the whole apparatus may reach one meter or more; the internal diameter sixteen millimeters. The apparatus weighs with a length of one meter, together with all its belongings, about two kilograms. For the investigation of peat and muck soils as well as sand, instead of the steel auger guide one of brass or copper can be used. For this purpose the length of the apparatus may reach three to four meters.

In comparison with other apparatus which are used for taking samples, it appears without doubt that with the one just described a better and less mixed portion of the soil can be obtained at great depths. The apparatus is said to have many advantages over a similar one known as Fraenkel’s, and is much more easy to clean. The advantages of the apparatus are said to be the following: The farmer with this piece of apparatus in a short time can go over his whole farm taking samples to the depth of ninety centimeters since a single boring does not take more than one minute. Geologists and others interested in the soil at greater depths can use an apparatus three to four meters in length and obtain unmixed samples from these lower depths. These are also interesting from a bacteriologic point of view. The entire apparatus is especially valuable for the investigation of the lower parts of peat and muck soils. The apparatus has been tried in the collection of samples for the laboratory of the Department of Agriculture and is too complicated to be recommended for ordinary use. When however samples are to be taken at great depths as in peat soils it is highly satisfactory.

78. Soil Sampling depends for its success more on the judgment and knowledge of the collector than on the method employed and the apparatus used. One skilled in the art and having correct knowledge of the purpose of the work will be able to get a fair sample with a splinter or a jack-knife while another with the most elaborate outfit might fail entirely in collecting anything of representative value.

There are some special kinds of soil sampling, however, which cannot be left to the method of the individual and it is believed that with the descriptions given above nearly all purposes for which samples are desired may be served.

For the study of nitrifying organisms, however, special precautions are required and these will be noted in a more appropriate place.

In taking samples for moisture determinations the method of Whitney is recommended as the best. For the general physical and chemical analytical work the standard methods are all essentially the same. The principles laid down by Hilgard will be found a sufficient guide in most cases.

TREATMENT OF SAMPLE IN THE LABORATORY.

79. The Sample, or mixed sample, taken by one of the methods above described, is placed on a hard smooth board, broken up by gentle pressure into as fine particles as possible and all pieces of stone and gravel carefully removed and weighed; all roots, particles of vegetable matter, worms, etc., are also to be weighed and thrown out. This can be done very well by using a sieve of from one to two millimeter mesh. Care should be taken that the soil be made to pass through, which can be accomplished by subjecting the lumps to renewed pressure with a rubber-tipped pestle. In the above operation the soil should be dry enough to prevent sticking. The relative weights of the pebbles, roots, etc., and the soil should be determined.

80. Order of Preliminary Examination.—Hilgard^[62] commences the examination of a soil sample by washing about ten grams of it into a beaker with a water current of definite velocity, stirring meanwhile actively the part carried into the vessel. The residue not carried by the current is examined macro- and microscopically to determine the minerals which may be present, and the condition in which the fragments exist—whether sharp or rounded edges, etc.

This examination will give some general idea of the parent rocks from which the sample has been derived and of the distance the particles have been transported. Next follows the hand test, viz., rubbing the soil between the thumb and fingers first in the dry state and afterwards kneading it with water and observing its plasticity. Following this should come a test of the relations of the sample to water, viz., its capacity for absorbing and retaining moisture. Finally the separation of the soil into particles of definite hydraulic value and a chemical examination of the different classes of soil concludes the analytical work.

81. Air Drying.—The sifted soil should be thoroughly mixed and about one kilogram spread on paper and left for several days exposed in a room with free circulation of air and without artificial heat. The part of the sample to be used for the determination of nitrates should be dried more quickly as described in another place. The sample is then placed in a clean, dry glass bottle, corked, sealed, and labeled. The label or note book should indicate the locality where the sample was taken, the kind of soil, the number of places sampled, and other information necessary to proper description and identification.

82. Caldwell^[63] directs that having taken the sample to the laboratory, the stones and larger pebbles should be separated from the finer parts by the hand, or by sifting with a very coarse sieve, and examined with reference to their mineralogical character, weight and size, making note, in this last respect, of the number that are as large as the fist or larger, the number as large as an egg, a walnut, hazel-nut, and pea, or give the percentage of each by weight.

Pulverize the air-dried soil in a mortar with a wooden pestle, and separate the fine earth by a sieve with meshes three millimeters wide; this sieve should have a tightly fitting cover of sheepskin stretched over a loop, and it should be covered in the same manner underneath, so that no dust can escape during the process of sifting.

Wash the pebbles and vegetable fibers remaining on the sieve with water, dry and weigh the residue; the water with which this gravel was washed should be evaporated to dryness at a temperature not exceeding 50° towards the close of the evaporation, and the residue mixed with what passed through the dry sieve.

The sifted fine earth is reserved for all the processes hereinafter described, and is kept in well-stoppered bottles, marked air-dried fine earth. The sieve mentioned above is too coarse for the more modern methods of analysis.

83. Wolff^[64] directs that the air-dried earth (in summer dried in thin layers at room temperature, in winter in ovens at 30° to 50°) be freed from all stones, the latter washed, dried, and weighed. The soil is next passed through a three millimeter mesh sieve, the residual pebbles and fiber washed, dried and weighed. The fine earth passing the sieve is used for all subsequent examinations. It is air-dried at moderate temperatures and preserved in stoppered glass vessels.

84. The French^[65] commission calls especial attention to the method of subsampling, and prescribes that the sample of earth which has been taken in the manner indicated, and of which the weight should be greater as the material is less homogeneous should not be analyzed as a whole. It should be divided into two parts. The first includes the finer particles constituting the earth, properly so-called, with the elements which alone enter into play in vegetable nutrition and on which it is necessary to carry out the analysis. The second embraces the coarser particles to which only a superficial examination should be given and which may have a certain importance from a physical point of view but which cannot take any part from a chemical point of view, in the nutrition of plants. It is, however, useful to examine its mineralogical constitution and to look for the useful elements such as lime, potash, etc., which it may be able to furnish to the earth, and in proportion as it is decomposed, finer particles which may be useful in plant nutrition.

How are we to distinguish between the fine and coarse elements? All grades of fineness are observed in the soil, from the particles of hydrated silica so small that with the largest magnifying power of the microscope it is scarcely possible to distinguish them, up to grains of sand which are of palpable size and visible to the naked eye, and extending to pebbles of varying sizes. All intermediate stages are found between these and if it should be asked what is the precise limit at which it is necessary to stop in distinguishing the fine from the coarse elements of the soil, the answer is that this can only be determined by a common understanding among analysts. In general, it may be said, that the mark of distinction should be the separation which can be secured with a sieve having ten meshes per centimeter.

85. Loose Soils.—Having agreed upon a sieve of the above size, the process of separation in loose soils is as follows: The earth is exposed to the air and when the touch shows that it is sufficiently dry the conglomerated particles should be simply divided without breaking the rocky material which exists in a state of undivided fragments. There are some special precautions to be taken. Rubbing in a mortar must be forbidden since it reduces the earth to particles which are unnatural in size, by securing the breaking up of the fragments consisting of the débris of rocks. When it is possible the earth should be rubbed simply in the hand and after having separated that which passes the sieve, the large particles which have not passed should be again rubbed with the hand, until all the particles which can be loosened by this simple treatment have passed the sieve. The separation should be as complete as possible in order that a sample of the particles passing the sieve should represent as nearly as possible, a correct sample of the fine particles of the soil.

In regard to the pebbles, they should be washed with water upon the sieve in order to carry through the last of the particles of earth adhering to them. They are then dried and their weight taken. The fine part of the earth is also weighed. On an aliquot part, say 100 grams, the moisture is determined and then by simple calculation the whole sample of the air-dry soil can be calculated to the dry state. The sample is then placed in a glass flask.

The pebbles are examined with a view of determining their mineralogical constitution; as for instance, on being touched with a little hydrochloric acid it can be determined whether or not they are carbonate of lime. The nature of the rock from which they have been derived is often to be determined by a simple inspection.

86. Compact Soils.—If the soils are not sufficiently loose to be treated as before described, it is necessary to have recourse to other means of division, which should not, however, be sufficiently energetic to reduce the rocky elements to fine particles. For this purpose the earth may be broken by means of a wooden mallet, striking it lightly and separating the fine elements from time to time by sifting. A wooden roller may also be used with a little pressure, for breaking up the particles or a roller made out of a large glass bottle. These methods will permit of a sufficiently fine division of the soil without breaking up any of the pebbles. Sometimes, however, a soil can not be broken up by such treatment. It is then necessary to have recourse to the following process: The soil is thoroughly moistened and afterwards rubbed up with water. The paste which is thus formed, is poured upon the sieve and washed with a stream of water until all the fine particles are removed. The wash water and the fine particles are left standing until the silt is thoroughly deposited when the supernatant water is poured off and the deposited moist earth is transferred into a large dish and dried on a sand or water-bath. In this way a firm paste is formed which can be worked up with the hand until rendered homogeneous and afterwards an aliquot portion be taken to determine moisture.

87. Method of Peligot.—The method recommended by Peligot^[66] for the preparatory treatment of the sample is essentially that already described. The sample is at first dried in the air and then in an oven at 120°. When dry and friable 100 grams are placed in a mortar and rubbed with a wooden pestle. It is then passed through a sieve of ten meshes per centimeter. The largest particles which remain in the sieve should have about the dimensions of a pin’s head. The stones are separated by hand. They should be shaken with water in order to detach any pulverulent particles adhering thereto. The turbid water resulting from this treatment is added to that which is used in separating the sand from the impalpable part of the soil.

88. Wahnschaffe prescribes^[67] in the further preparation of the sample for analysis that the coarse pieces up to the size of a walnut be separated in the field where the sample is taken and their relative weight and mineralogical character determined. The soil sample is then to be placed in linen or strong paper bags and carefully labelled. In order to avoid any danger of loss of label the description or number of the sample should be put on the cloth or paper directly.

The sample when brought to the laboratory should be spread out to dry, in a room free of dust. In the winter the room should be heated to the usual temperature. The air drying should continue until there is no sensible loss of weight. The samples then are to be placed in dry, glass-stoppered glass bottles where they are kept until ready for examination. This method of keeping the samples avoids contact with ammonia or acid fumes with which a laboratory is often contaminated.

89. The Swedish chemists^[68] direct that samples which are to be used for chemical examination in the manner described below, are most conveniently brought to such a condition of looseness and humidity that the soil feels moist when pressed between the fingers without, however, sticking to the skin. To prepare the sample in this manner, spread it in a large porcelain dish or on a glass plate in a place where it is not reached by the laboratory atmosphere; stir it frequently till it assumes the mentioned humidity (if the sample when sent is too dry, moisten it with distilled water till its condition is as indicated); then pulverize carefully between the fingers and finally sift through a sieve with five millimeter holes. In this way free the sample from stones, undecayed roots and similar parts of plants, pieces of wood, and other matter strange to the soil, which remain on the sieve; mix the sample carefully and put it into a glass bottle provided with a stopper well ground in; keep it in a cool place. Samples prepared in this way will usually contain 20–30 per cent moisture; boggy soils 60–80 per cent and peat soils 50 per cent.

90. Petermann^[69] follows the method below in preparing samples of soil for analysis.

The soil is gently broken up by a soft pestle and all débris if of organic nature, cut fine with scissors. About 2500 grams of this soil are passed through a one millimeter mesh sieve. The organic débris is removed by forceps, washed free of adhering earth dried at 120° and weighed. The nature of the organic débris should be noted as carefully as possible.

The pebbles and mineral débris not passing the sieve are worked in a large quantity of water by decantation. They are also dried at 120° and weighed. This débris is examined mineralogically and thus some idea of the origin of the soil obtained.

91. The various methods for the preliminary treatment as practiced by the best authorities have been somewhat fully set forth in the foregoing résumé. The common object of all these procedures is to get the soil into a proper shape for further physical and chemical examination and to determine the comparative weights of foreign bodies contained therein.

The essential conditions to be observed are the proper sifting of the material and avoidance of mechanical communition of the solid particles too large to pass the meshes of the sieve. If possible the material should be passed through a sieve of one millimeter mesh. In cases where this is impracticable a larger mesh may be used, but as small as will secure the necessary separation. Before final chemical analysis a half millimeter mesh sieve should be employed if the soil be of a nature which will permit its use. Over-heating of the sample should be avoided. Rapid drying is advisable when the samples are to be examined for nitrates.

The method recommended by the French commissions seems well adapted to the general treatment of samples, but the analyst must be guided by circumstances in any particular soil.

AUTHORITIES CITED IN PART SECOND.