SOILS — FERTILIZERS. 27 



this requirement. Of course seasonal variations make close approximations 

 in this respect impossible, but the actual differences due to this factor are 

 thought to be comparatively small. 



A report on the phosphate fields of South Carolina, W. H. Waggaman 

 (U. S. Dept. Agr. Bui. 18, pp. 12, pis. S, fig. i).— The history of these deposits 

 is briefly reviewed and their location, extent, character, and exploitation are 

 described. "The phosphate region lies along the coast in a belt extending 

 from the Wando River, in Charleston County, to the Broad River, in Beaufort 

 County. The rock is of Tertiary age and is usually divided into two classes, 

 namely, the land deposits and the river deposits. These classes, however, are 

 practically identical, the latter being merely the former washed into the river 

 beds. . . . 



" With the exhaustion of the more accessible deposits and the discovery of 

 higher grade phosphates in Florida and Tennessee, the output from South 

 Carolina has fallen off considerably. River mining has entirely ceased, and 

 only two companies are mining the land rock. The total output in 1911 was 

 169,156 tons. . . . 



" The general opinion has been that the phosphates of South Carolina are 

 practically exhausted. This is far from being the case. There are thousands 

 of acres of rich phosphate land still practically untouched. Although the 

 phosphate on much of this property is covered by a heavy overburden, more 

 efficient mining methods and improved market and transportation conditions 

 would render it all available." 



Thomas slag, its preparation and use, J. P. Wagneb (Monatsher. Gesell. 

 Ford. Wiss., Ackerb. u. Kiinste Unter-Elsass, lf( {191S), No. S, pp. 126-168, 

 figs. 27). — The process of manufacture of Thomas slag is described in some 

 detail, and its use as a fertilizer is discussed. 



Analyses of Thomas slag from different sources, H. von Feilitzen and 

 I. LuGNER iChem. Ztg., 57 {191S), No. 68, pp. 689, 650).— Analyses of a number 

 of samples of Thomas slag are reported, showing a much smaller content of 

 free lime than is indicated by the older anlyses. There was no great variation 

 in the composition of slag from different sources. 



Kelp and other sources of potash, F. K. Cameron {Jour. Franklin Inst., 

 116 (1918), No. 4, pp. S41f-S8S, figs. i5).— This article discusses briefly other 

 sources of potash, but deals in detail with the utilization of the Pacific coast 

 kelps for this purpose. The more important species of kelps from the ferti- 

 lizer standpoint, the location and extent of the kelp groves, the composition and 

 fertilizing value of kelp, and methods of harvesting and handling the material 

 are described. Data are also given as to the present status and future possi- 

 bilities of the kelp industry on the Pacific coast. 



Lime, B. H. Hite {West Virginia Sta. Circ. 6, pp. 16, figs. S). — This circular 

 discusses in a popular way the effects of lime on the soil and gives Information 

 as to how it may be obtained and used. 



On the influence of the ratio of lime to magnesia on plants, O. Loew {Jour. 

 Indus, and Engin. Chem., 5 {1918), No. 11, pp. 959, 560).— This is a reply to an 

 article by Gile and Ageton already noted (E. S. R., 28, p. 812). 



Is silica an indispensable constituent of plant food? M. Lundie {So. 

 African Jour. Sci., 9 {1913), No. 10, pp. 265-268).— Earlier investigations on 

 this subject are briefly reviewed and water culture experiments by the author 

 are reported. The results of the latter indicated that silica is not essential as 

 a plant food, but suggested that when deposited in the cell membrane and in the 

 epidermis of the plant it might afford a certain protection against fungus 

 disease (rust). 



