American Geographical Society

Introduction À L'étude de la Latéritisation et des Latérites du Centre Africain by G.WaegemansReview by: Robert L. PendletonGeographical Review, Vol. 42, No. 2 (Apr., 1952), p. 321Published by: American Geographical SocietyStable URL: http://www.jstor.org/stable/211400 .

Accessed: 09/05/2014 01:13

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

American Geographical Society is collaborating with JSTOR to digitize, preserve and extend access toGeographical Review.

http://www.jstor.org

This content downloaded from 169.229.32.137 on Fri, 9 May 2014 01:13:40 AMAll use subject to JSTOR Terms and Conditions

GEOGRAPHICAL REVIEWS 321

important as maize or beans. There are various races with distinctive geographical distri- butions, and the uses of some of the grain amaranths are unusual. They are embedded in ritual and include such special preparations as popping. The distribution of the Mexican and Peruvian races in Southeast Asia in the hands of the primitive hill people from Szechuan through Tibet and India poses again the problem of very early pre-Columbian contacts with America. The American grain amaranths are today known in Szechuan by a name applied to amaranths in this same area as early as A.D. 950. Sauer is cautious. His evidence is not conclusive, but his data strongly suggest important early Asiatic-American contacts. -GEORGE F. CARTER

INTRODUCTION A L'ETUDE DE LA LATERITISATION ET DES LATERITES DU CENTRE AFRICAIN. By G. WAEGEMANS. Map, diagrs., ills., bibliogr. Btull. 4gric. dti Conigo Belge, Vol. 42, I95I, pp. I3-56.

To emphasize the divergent and often strongly conflicting definitions of laterite and the hypotheses as to what the process or processes of laterization really are, Waegemans in this work endeavors to state briefly the bewilderingly different points of view of many writers. Significantly, he concludes that the use of the silica, sesquioxide or similar ratios or the presence of free alumina in the soil is not of importance in estimating the degree of "lateritization" or in determining whether or not a soil should be called a "laterite." The well-documented discussion of the main groups of clay minerals and where and how they are formed leads the author to propose a new hypothesis: that the origin of the clay minerals is to be found where the primary parent rocks are weathering under conditions of permanent saturation. Observations in the Belgian Congo, in Madagascar, and in Brazil suggest that kaolin in quartz-rich sediments does not change under climatic action; on the other hand, soils weathered especially from mafic igneous rocks are especially profoundly "lateritized." North of Matadi, in the Lower Congo, Waegemans sampled and analyzed a profile I7 meters deep, down through a strongly laterized soil to the igneous parent rock. (The reviewer has seen this soil and agrees that it is a laterite.) Thermal analyses of the clay in all the samples showed conclusively that kaolin forms directly from the parent rock; 23 of the curves are reproduced. The author concludes that "lateriti- zation" of soils should not be considered as a mineralization of the clay fraction but as a phenomenon affecting the secondary constituents of the soil other than the clay minerals of the kaolinite type. Thus Vine (H. Vine: Nigerian Soils in Relation to Parent Materials, Proc. First Cotttmnonwealth Cotnference on Tropical and Stub-Tropical Soils, 1948 [Comnmon- wvealth Buir. of Soil Sci. Tech. Commttnication No. 46], p. 22) is correct in believing that there is not a progressive decomposition of silicates and accumulation of sesquioxides while silica is washed away, and that the more highly sesquioxidic "laterites" do not represent a more advanced stage of the process than do the "lateritic earths."-ROBERT L. PENDLETON

THE SEA AROUND US. By RACHEL L. CARSON. vii and 230 PP.; maps, diagrs., bibliogr., index. Oxford University Press, New York, i19I. $3.50. 81 x 512 inches.

That readability, artistic merit, and scientific worth are not mutually exclusive attributes of popular science writing has been amply demonstrated by such writers as Gamow in physics and Bell in mathematics. Such works are not only entertaining reading for the

This content downloaded from 169.229.32.137 on Fri, 9 May 2014 01:13:40 AMAll use subject to JSTOR Terms and Conditions