422 EXPERIMENT STATION RECORD. 



to be absorbed or dissolved, and in which the quantities of nitrogen in a state 

 of solution or abs()ri)tion were observed when (1) with a constant quantity 

 of nitrogen and of absorption medium the quantity of solution medium was 

 varied, and (2) with a constant quantity of nitrogen and of solution medium 

 the quantity of absorption medium was varied. 



The results obtained were found by the author to conform, within the limits 

 of error, to the mathematical law for absorption / (X—x)=C—k.B, where X 

 is the maximum of absorbable nitrogen, x the salt absorbed at the time by the 

 mass of soil B, and C and 1c arc constants, and to the mathematical law for 

 solution f ii/ — «) = / (Y—a) — c.B, In which y denotes the salts in solution in 

 the given quantity of water with the existing mass of earth B, and Y, a, and c 

 are constants. Since every law holds good only with constant temperature 

 regardless of its degree, these laws are designated as absoiTition or solution 

 isotherms. 



In the author's opinion these equations afford an insight into the varying 

 interaction between plant foods and water and soil, owing to the fact that they 

 reveal the extent to which salts are reversibly or irreversibly dissolved or ab- 

 sorbed and thus disclose the maximum soluble and absorbable quantities and 

 the saturation concentration of the solution under given constant conditions. 



The effect of carbon dioxid on plant growth and soil formation, G. 

 Mettler (Ztschr. Sauerst. u. Sticlcst. Indus., No. 5 {1913), p. 193; abs. in 

 Chcm. Ztg., 37 {1913), No. IO4, Report., p. 469; Chem. Ahs., 8 {191.',), No. 22, 

 p. 3101). — The effect of carbon dioxid in the soil in promoting plant growth is 

 attributed to the formation of the necessary carbon, nitrogen, and organic salts 

 resulting from the increased activation of oxygen by the carbon dioxid. The 

 author suggests the formation of carbon pernitrid, CN*, as a probable cause of 

 the spontaneous combustion of coal beds. 



The effect on plant growth of saturating a soil with carbon dioxid, H. A. 

 NoYES {Science, n. scr., 40 {191.',), No. 1039, p. 792).— It was found that this 

 treatment was injurious to tomato and corn plants. "A carbon dioxid satu- 

 rated soil upset the growth of these plants but did not change the soil so that 

 the plant could not grow after its application was discontinued."' 



The proof of the origin of smoke acids in rain water flowing down tree 

 trunks by means of an automatic separator and the influence of these acid 

 waters on the soil, U. Gerlach {Samml. Ahhandl. Abgasc u. RduchschUdcn, 

 No. 9 {1914), PP- -Hy P^s. 6). — The author reports experiments with his so-called 

 smoke and water separator in different localities Avith reference to the smoke 

 content of the air; and also cropping experiments and soil investigations to 

 determine the effect of rain water containing smoke acids on soil and vegetation. 



The smoke and water separator is designed primarily to catch the rain water 

 which runs down the trunks of trees, but may also be used in the open. The 

 amount of flow of rain water down tree trunks was found to be large in many 

 cases and varied according to the size and shape of the tree. For trees in leaf 

 it averaged only about one-third of that for bare trees. The apparatus per- 

 mitted the collection of rain waters from different smoke sections separately, 

 the determination of the extent of their acidity by means of litmus paper and 

 chemical analysis, and .their separation according to the sources of the smoke. 



In the cropping experiments the so-called smoke sickness of soil was first 

 evidenced in a retardation of germination, particularly of fruit trees and the 

 legumes vetch and beans. The legumes developed more slowly and sparsely 

 and lived a shorter period in smoke-^ick than in normal soils, while in the fii'st 

 year there was no api)areut difference in the development of pine and fir ever- 

 greens. On discontinuing the use of water containing smoke acids and making 



