958 EXPERIMENT STATION RECORD. 



products of weathering mainly because the extraction of silica is incomplete. This 

 can be obtained by alternate extraction with acids and with alkali solutions. The 

 author's method involves in general successive treatment with hydrochloric acid 

 (3 to5 gin. of soil with 50 to 100 cc. of acid), increasing in strength from 1.035 to 1.2 

 sp. gr. at temperatures rising from 55° C. to boiling for periods varying from 5 minutes 

 to 1 hour, followed by 2 extractions for 5 minutes at . r i5° C. and I hour at boiling 

 temperature, respectively, with sodium or potassium hydroxid solution of 1.04 sp. gr., 

 and finally in some cases heating with concentrated sulphuric acid (5 to 10 cc. ) until 

 the larger part of the acid is evaporated. In case of very basic soil the treatment 

 with alkali precedes that with acid and is continued for a longer time than that given 

 above. The insoluble residue is examined microscopically. 



This method has been used in a study extending over many years of the clay soils 

 of the recent alluvium of the Netherlands and of the volcanic soils of Sumatra and 

 Java, in which the author has attempted to ascertain the relation between silica and 

 alumina, their chemical combination in products of weathering, and whether they 

 have a definite solubility in acids and alkalis; to determine whether products of 

 weathering contain alkaline bases; and whether the iron oxid of soils is free, or 

 absorptively, or chemically combined. 



The results of studies of a large number of alluvial plastic clays, soils of volcanic 

 origin, and laterite soils, which are summarized, show that the ratio of alumina to 

 silica is not constant. With the ordinary alluvial clays the results indicated that the 

 weathering had taken place in a single stage, while with the volcanic and laterite soils 

 there were various stages of weathering resulting in a mixture of silicates. The 

 progress of weathering was best shown in the laterites, the final product being 

 hydrargillit. Alkaline and alkaline earth bases were present in varying amounts, 

 diminishing with the progress of weathering. The ordinary clays contained much 

 loosely combined water — lost at 15° 0. over concentrated sulphuric acid — and about 

 2 molecules of water which was lost at higher temperatures. The laterites examined 

 apparently contained little loosely held water and more than 2 molecules of firmly 

 fixed water only when hydrargillit was present. The more basic the products of 

 weathering the more readily they dissolve. The iron oxid of the soils examined 

 contained a little more than i molecule of water at ordinary temperature and a little 

 less at 100° C. 



The importance of a fixed relation between amount, strength, and temperature of 

 solvent, and the amount of soil, etc., is emphasized. The constitution of the prod- 

 ucts of weathering as well as the process itself are discussed. 



Index to the mineral resources of Alabama, E. A. Smith and H. McCalley 

 {University, Ala.: Geological Survey of Alabama, 1004, pp. 79, pis. 6, map 1). — "This 

 document is intended rather to direct the attention of those interested to the various 

 natural resources of the State which are considered capable of being profitably util- 

 ized, and to the sources from which more detailed information may be derived, than 

 to be a complete or adequate presentation of the subject." 



The mineral products noted are classified under (1) materials used in the manu- 

 facture of iron, (2) clays and cements, (3) miscellaneous, the latter including among 

 other materials the following, which are of special interest from an agricultural stand- 

 point: Niter, phosphates (silurian, cretaceous, and tertiary), building stones, road 

 and ballast materials, and soils. 



"For convenience in the discussion of its soils, the State may be divided into two 

 parts, approximately coextensive with the mineral district and the agricultural dis- 

 trict, respectively. 



" In the first the soils are in the main residual, i. e., they have been derived from 

 the rocks upon which they now rest, and show, therefore, more or less close relation- 

 ship to them. In the second, the Coastal Plain or agricultural district, the creta- 

 ceous and tertiary formations have been overspread with a mantle of sandy loam 



