216 EXPEEIMENT STATION EECOED. 



one of eliminating the uncertainty of tlie rainfall as a factor in decomposing 

 the buried green material, include the possibility of applying the fermented 

 manure at the best rate per acre and at the best time for producing its optimum 

 manurial effect ; at the same time it is not necessary to grow the green manure 

 crop on the land which is to carry the . . . crop intended to benefit by its 

 manurial effect." 



Brief reference is made to a modified method of biological analysis of soil in 

 which the biological activities are studied with large samples (400 to 1,200 gm.) 

 of soils instead of with 1 gm. samples as is the method commonly employed. 



Experiments on the lateral percolation of contamination in soil, O. Bail 

 and P. Breinl (Arch. Hw-, 82 (1914), No. 1, pp. 33-56, figs. 7).— Experiments 

 on the lateral percolation of contaminated liquids in soils of different mechanical 

 and physical structures are reported. 



Percolation was more or less influenced by the soil structure as regards size 

 .,of soil grain, pore space, permeability, nature of stratification, and moisture 

 content. In tests of both short and long duration, using small and large ap- 

 paratus and correspondingly large and small soil samples, the soil section being 

 dampened assumed the shape of a more or less iri'egular triangle, whose base 

 was the wall at the entrance of the liquid to the soil, and whose apex was the 

 most distant point of lateral percolation. Where downward infiltration was 

 unhindered the lateral percolation attributed to the pressure head was small, 

 but when constantly hindered by an impervious layer a horizontal sheet of 

 contaminated liquid was formed. With increasing depth of downward infiltra- 

 tion, due to gravity, the lateral spread of the contaminated surface due to 

 capillarity was very marked. Contaminated liquids were purified to a limited 

 degree through filtration and absorption by soils. 



It is concluded that if downward infiltration is unhindered the danger of 

 pollution of the ground water lies in the resulting lateral spread of the con- 

 taminated surface due to capillarity. 



The effect of hydroxyl ions on clay and clay soils in marling, J. G. Masch- 

 HAUPT {Landw. Vers. Stat., 83 {1914), No. 5-6, pp. 467-470, pi. i).— The author 

 maintains that the flocculating effect of calcium hydroxid on clay suspensions 

 is due principally to the calcium ion rather than to the hydroxyl ion. He 

 found that both sodium hydroxid and sodium carbonate solutions had a floc- 

 culating effect on clay suspensions only in strong concentrations and when very 

 dilute had a stabilizing effect, while calcium hydroxid had a flocculating effect 

 when both dilute and concentrated. He concludes, therefore, that the flocculat- 

 ing effect of calcium hydroxid and sodium hydroxid can not be attributed 

 entirely to the same causes. 



Studies of plant growth in heated soil, G. W. Wilson (Biochem. Bui., 3 

 (1914), No. 10, pp. 202-209, pis. 3). — Pot experiments with buckwheat, wheat, 

 rye, and barley, using a very poor loam soil which had previously been heated 

 to 95, 135, and 175° C, are reported. 



The growth and vigor of all the crops, particularly the buckwheat, were accel- 

 erated on soil which had been heated to 95°, but were retarded on soils heated 

 to 135 or 175°, especially the latter. Plants grown on heated soil were more 

 susceptible to attack by parasitic fungi than those grown on uuheated soil, and 

 soil fungi grew more abundantly on soils which had been subjected to high 

 temperatures. 



It is concluded that " the effect of heating soils upon the crop grown varies 

 with the temperature to which the soil is subjected, the kind of soil used, and 

 the nature of the crop grown upon it." 



See also a previous note by Bouyoucos (E. S. R., 29, p. 618). 



