No. 6. DEPARTMENT OF AGRICUL.TURE. 318 



I, is used. It consists of a circular plate of copper, six inclies in 

 diameter, in the centre of wliich is a circular hole, one and a fourth 

 inches in diameter, from which rises at right angles to the plate a 

 copper tube of the same diameter and twelve inches long. The 

 ground where the boring is to be made is cleared of all vegetation 

 and the copper plate set firmly and held in place by both feet. 

 The auger is then inserted into the copper tube, which should stand 

 vertical to the ground surface, and the auger turned until the re- 

 quired depth is reached, as determined by graduations on the stem of 

 the auger. The auger is then drawn gently from the ground and 

 into the copper tube until the core of earth is enclosed in the latter, 

 and thus kept intact. The earth is then emptied on a sheet of clean 

 paper. 



In getting an average sample for an entire field, borings should be 

 taken along two intersecting lines diagonally across a field at in- 

 tervals of ten or twenty feet according to the size of the plot. These 

 separate borings are emptied into a clean box until the work is fin- 

 ished. The collected soil is then sifted through a No. 10 sieve, reduc- 

 ing the lumps but discarding stones and gravel. The sifted soil is 

 then very thoroughly mixed, and from this a sample of about two 

 pounds is taken to the laboratory. 



The latter sample is lifted through a brass sieve of a one-milli- 

 meter mesh, and any lumps or coarse particles are reduced in a mor- 

 tar until the entire sample has been made to pass the meshes of the 

 sieve. The whole is then very thoroughly mixed and from this a 

 small sample of about twenty grams is taken. This is then sifted 

 through a 0.5 millimeter brass sieve which has been made sterile in 

 a bath of boiling water, and dried over the bare flame of a bunsen 

 burner. Any lumps or coarse particles which do not readily pass the 

 sieve are rubbed in a sterile mortar until the last portion has passed. 

 The sittings are then thoroughly mixed, transferred to a sterile test- 

 tube and tightly corked. 



^. Making the analysis. In a weighed glass-stoppered weighing- 

 bottle approximately 0.5 a gram of the sample is placed, and the 

 exact weight determined. The soil sample is transferred to a small 

 sterile mortar and with a small quantity of sterile water rubbed to 

 a fine mud, after which the last trace of soil in the weighing-bottle 

 is transferred to the mortar by washing with sterile water. 



The supernatant muddy water in the mortar is then transferred to 

 a 100 c. c. flask containing sterile water; more water is added and 

 the residue triturated; again transferred to the flask, and the opera- 

 tion continued until all of the soil in a finely divided state has been 

 washed into the flask. The latter is then filled to the 100 c. c. mark 

 with sterile water, and the contents vigorously shaken for exactly 

 two minutes. One c. c. of this turbid water is then transferred to a 



