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National Geographic : 1897 Apr
Contents
GEOGRAPHIC LITERATURE A Treatise on Rocks, Rock- Weathering, and Soils. By George P. Merrill, Curator of Geology in the National Museum, etc. Pp. xx + 411, with numerous illustrations. New York: The Macmillan Company. 1897. $4.00, net. During the present generation a score of students in this and other countries have turned attention to the soil; and, while it may be ques tioned whether they have yet succeeded in organizing a science of the soil, it may be affirmed that they have made substantial contributions toward such a science. Hitherto most of the publications pertaining to the subject have been technical or at least special, and confined to official documents; but now comes Professor Merrill, already favorably known through professorial work and genePal writing, with a popular work on soils adapted to both class work and general reading. His apology for the publication-" It is believed that no apology is necessary even in this day of many books for bringing out the present work "-emphasizes the importance of the subject: Human life and the ancillary animal and vege tal life of the land depends on the soil; the fullness of the earth is its wealth in soil; and the worthiest science-albeit in very infancy yet-is that pertaining to this richest of all natural resources. Every student, every teacher, every citizen, every statesman, ought to welcome such a contribution to human progress as this useful treatise. The work is arranged in five parts, each divided into several chapter lets. In the first part rocks are discussed as to their constituents, their physical and chemical properties, and their modes of occurrence, and in the second they are classified as (1) igneous, (2) aqueous, (3) aeolian, and (4) metamorphic; thus this part of the work deals with rock-making, and sets forth the laws involved in the development of the fundamental constituents of the external earth. The next two parts are devoted, re spectively, to the weathering of rocks and to the transportation and redeposition of rock debris, and in them the unmaking and remaking of rocks are admirably though briefly expounded. Part V, in which the originality of the work is concentrated, is entitled "The Regolith;" under this new term (derived from Greek words for blanket and stone) the unconsolidated material mantling the hard rocks is discussed in detail. The warrant for introducing a new word for the soils, subsoils, and other superficial materials of the earth arises in daily need; several terms have already been employed-" soil," "earth," etc., in general, "drift," "dilu vium," "alluvium," etc., for transported material, and " residua," " terra rossa," " gruss," "geest," "saprodite," etc., for the products of rock de cay-among laymen and scholars, but none has thus far proved satisfac tory. Merrill's suggestion is better than any that has gone before, but it remains to be seen whether his term will survive or fall into the ever yawning grave of desuetude. The author proceeds to classify the regolith as (1) sedentary and (2) transported; the former is subclassed as (a) re sidual deposits and (b) cumulose deposits, while the latter is divided into (a) colluvial deposits, (b) alluvial deposits, (c) aeolian deposits, and (d) glacial deposits. In addition, the soil proper is described, as a product rather than a deposit, with respect to chemical composition, mineral con stitution, and physical condition, as well as with respect to weight, color,
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