450 EXPERIMENT STATION RECORD. 



machine at the same speed a second time. Thus freed from the finer grades it is 

 transferred with a little clear water to a weighed dish and is dried and weighed as 

 coarse silt. The muddy water from this elutriation is run through the machine at 

 such speed of centrifuge and water current as will effect the separation of the next 

 size of particles, 0.00316 mm., namely, 95.73 cc. and 1,148 revolutions per minute. 

 The sediment is shaken up once and run through at the same speed, then collected 

 and weighed as medium silt. 



In a similar manner separation is made at the required speed of the fine silt, 0.001 

 mm. particles. The material remaining in suspension at the end of the process is pre- 

 cipitated by the addition of a solution of sodium chlorid (50 cc. of saturated brine to 

 1 liter < >f the water containing suspended material ) . After standing 4 hours, or better 

 over night, the water is siphoned off, the sediment collected, dried, and weighed, and 

 the salt in it determined volumetrically with silver nitrate solution (1 cc. equivalent 

 toO.Olgm. NaCl). 



From the results of a series of tests of the apparatus under a variety of conditions 

 the conclusion is drawn that "the advantages which the writer thinks should com- 

 mend this new machine for the mechanical analysis of soils are the rapidity with 

 which separations can be completed and the small sizes of grains which can be 

 separated and estimated. Very great accuracy is not claimed for the method, and 

 indeed such can hardly be claimed for any method yet proposed. It is the opinion 

 of the writer that very great refinement in the determinations of the several grades 

 of soil particles has but little value above that in determinations which are accurate 

 within one or two per cent." 



The effect of soil sterilization upon the development of plants, C. Schulzk 

 (Jahresber. Ver. Vertreter Angew. Bol, 1 (1903), pp. 37-44; abs. in Bot. Centbl, 95 

 (1904), No. 22, p. 586). — On account of the fact that many experiments are carried 

 on in soil sterilized by heat, the author has investigated the effect of high tempera- 

 tures on the soil compounds. It was found that a sterilizing temperature affects the 

 decomposition products of some soils in a way that is detrimental to plant growth, 

 in some of the experiments the plants proving exceedingly sensitive to the changes 

 produced. On the other hand, sterilization of soil by fi^at results in the liberation 

 of soil compounds, especially the insoluble nitrogen compounds, resulting in a greatly 

 increased growth of the plant when compared with plants grown in normal soils. 



An artificial root for inducing capillary movement of soil moisture, L. J. 

 Briggs and A. G. McCall (Science, n.ser., 20 (1904), No. 513, pp. 566-569) .—The 

 apparatus here described was devised for the purpose of studying the rate at which a 

 plant is able to secure water from a soil. It consists of a Pasteur-Chamberland filter 

 tube connected by means of a short piece of lead tubing to a 2-liter bottle exhausted 

 to pressure equal to the vapor pressure of water. The filter tube is buried in the soil 

 which is to be studied, but preparatory to doing this "a core of soil is removed by 

 means of a tube, the external diameter of which is equal to that of the smaller end 

 of the porcelain tube. The filter tube is slightly conical in form, so that when it is 

 forced into this hole a good capillary connection is established between the walls of 

 the tube and the soil." 



In the investigations reported "the apparatus was usually allowed to stand for 

 about 24 hours, when the exhausted bottle was detached and the water which had 

 been drawn into the apparatus removed and measured. The porcelain tube was not 

 disturbed in removing the water, which was drawn into a small flask by suction 

 through a fine tube extending to the bottom of the porcelain tube. The apparatus 

 was then immediately put together again and exhausted by means of an aspirator. 



"The water thus removed not only represents the amount of water which the soil 

 has supplied to the tube during the preceding period of 24 hours, but it appears to 

 be identical in concentration and composition with the soil solution from which the 

 plant obtains its food. Therefore, the determination of the amount and composition 



