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. 26.-"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 both the Standard and Century dictionaries as 

 (1) a bed derived from rock decay in situ, (2) high gravelly land, and (3) 

 gravel or drift. The term gruss, although advocated by some American 

 authorities, is of old German origin and open to the same objection. 



"^ Bull. 52, U. S. Geol. Survey and Ann, Eep. IT, S. Geol. Survey, 1884-85. 

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