3338 DYNAMICAL GEOLOGY. - [Boox IIL — 
istic layer occurs on a limited scale over the chalk of the south-east — 
of England, where, with its abundant flints, it lies as the undissolved 
ferruginous residue of the chalk that has been removed to a depth of 
many yards. It occurs likewise in swallow-holes and other passages 
dissolved out of calcareous masses, and forms the well-known red- 
earth of bone caves. In south-eastern Europe it plays an important 

Fic. 91.—Tue “ KerrLe anp Pans,” St. Mary, Scitiy, CAVITIES WEATHERED OUT 
oF GRANITE (B.). 
part among superficial deposits, being extensively developed over the 
limestone districts, especially in Istria and Dalmatia, where it is 
known as the ferruginous red earth or ¢erra rossa.* 
Other remarkable examples of similar subaerial waste have 
been specially noticed among crystalline schists and eruptive rocks. 
In South America, it has been remarked with astonishment that 
the rocks are sometimes decayed to a depth of more than 300 feet.” 
In the southern portions of North America and in Central Asia the 
same fact has been observed. Pumpelly has specially drawn atten- | 
tion to the geological importance of this prolonged disintegration — 
in sitt, He points out that as masses of decomposed rock may be 
observed to a depth of over 100 feet, the surface of the still solid 
rock underneath presents ridges and hollows, succeeding each other 
according to varying durability under the influence of percolating 
carbonated water. In this kind of weathering, where erosion does 
not come into play, it is evident that the resulting topography must, 
in some important respects, differ from that of an ordinary surface of 
superficial denudation. In particular, as Pumpelly shows, rock basins 
may be gradually eaten out of the solid rock. These will remain full 
of the decomposed material, but any subsequent action, such as that 
of glacier iee which could scoop out the detritus, would leave the 
basins and their intervening ridges exposed.? 
1 On the origin of “ Terra rossa,” see M. Neumayr, Verhandl. Geol. Reichsanst. 1875, 
p. 50. Th. Fuchs, op. cit. p. 194. EK. von Mojsisovics, Jahrb. Geol. Reichsanst. xxx. 
(1880), p. 210. It is included among the ferruginous deposits by Stoppani (“ Corso 
di Geologia,” iii. p. 554). 
2 Liais, “ Géologie du Brésil,” p. 2. Ann. des Mines, 7me scr. viii. p. 628, 
* Pumpelly, Amer. Journ. Sci. 3rd ser. xviii, 1386; also postea, p. 416. 

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