. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. SEDENTARY MATERIALS: RESIDUARY DEPOSITS 289. ondary rocks, since those of drift origin are but derived from sedentary materials through the transporting agencies of air and water. They may be conveniently divided into two classes, (1) residuaP and (2) cumulose. (1) Residuary Deposits. — Under this name, then, are included all those products of rock degenera- tion which are to-day found occupying the sites of the rock masses from which they were derived, and immediately overlying such portions as have as yet escaped destructio
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. SEDENTARY MATERIALS: RESIDUARY DEPOSITS 289. ondary rocks, since those of drift origin are but derived from sedentary materials through the transporting agencies of air and water. They may be conveniently divided into two classes, (1) residuaP and (2) cumulose. (1) Residuary Deposits. — Under this name, then, are included all those products of rock degenera- tion which are to-day found occupying the sites of the rock masses from which they were derived, and immediately overlying such portions as have as yet escaped destruction. The name is peculiarly ap- Fig. ;Sliowing angular outlines of re- propriate, since they are siduary particles from decomposed gneiss. actually residues, left be- ^^ ^^'^' ^' ^'^^'^^'' ^' ^^^^^'- hind while the more soluble portions have been leached away by meteoric waters. The residual deposits of North America reach their maximum development in the portion of the United States east of the Mississippi and south of the southern margin of the ice sheet of the Glacial epoch. Their mode of accumulation and general characteristics have been very thoroughly discussed by Professors Eussell, Chamberlin, and Salisbury,^ on whose papers we shall draw for some of the facts given here. ^ Various names liave from time to time "been proposed for deposits of this nature, but obviously it is impossible to include under a single lithological term materials so widely variable. The term saproUte (from tlie Greek (rairpos, rotten, recently suggested by G. F. Becker, 16tli Ann. Rep. U. S. Geol. Survey, Part III, p. 289) is objectionable as conveying tlie idea of putridity. Moreover although resulting from the rotting of rocks the soil cannot, in itself be considered as rotten. The old provincial term geest adopted by De Luc, and recently endorsed by McGee (11th Ann. Eep. IT. S. Geol. Survey, 1889-90, p. 279), has lost whatever precise meaning it may have had, being defined in bo
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