54 C. R. VAN HISE 



magma to within the crust or upon its surface is not a cause for 

 crustal corrugation in addition to that produced by the transfer 

 itself. 



Cementation. — Another cause which explains crustal corruga- 

 tion is cementation (see pp. 34-35). In this process material is 

 carried in a direction opposite to the transfers of vulcanism. 

 In the outer zone of disintegration and decomposition material 

 is everywhere taken into solution by underground waters, and 

 carried to the openings below, where a part of it is deposited. 

 Although the zone of solution which supplies the material at 

 any time is narrow, material never fails, because this outer zone 

 is ever migrating downward. Wherever at moderate depth 

 during the process of deformation openings form, unless they 

 are occupied by magma, they are gradually filled by water 

 deposits, and thus there is local lateral extension, as in the case 

 of vulcanism. The amount of material which thus migrates 

 downward by means of underground waters cannot be quanti- 

 tatively estimated, but it is certain that it is enormous. 1 In 

 many regions where much deformed, comparatively deep-seated 

 rocks have been brought to the surface, it is found that a mea- 

 surable, and in some cases a considerable percentage of the entire 

 space was once unoccupied and has been filled by cementation. 

 The cemented rocks thus become a unit, which may be later 

 deformed themselves, or transmit the thrusts to adjacent rocks, 

 which may be deformed. In either case the shortening of the 

 original material is compensated, at least in part, by the exten- 

 sion due to the cement, and thus the crustal corrugations are 

 partly explained by water transfers of material. 



Change of oblateness. — Peirce 2 and Darwin 3 have shown that as 

 a result of tidal retardation the speed of rotation of the earth is 

 decreasing, and that in the far distant past it rotated much more 



1 Earth movements, by C. R. Van Hise : Proc. Wis. Acad. Sci., Arts, and Letters, 

 Vol. XI, 1898, pp. 511-512. 



2 The contraction of the earth, by B. Peirce : Proc. Am. Acad. Arts and Sci., Vol. 

 VIII, 1873, pp. 106-108 : Reprinted in Nature, Vol. Ill, 1871, p. 315. 



3 On the precession of a viscous spheroid, and on the remote history of the earth, 

 by G. H. Darwin : Phil. Trans. Roy. Soc, Vol. CLXX, Pt. II, 1879, p. 535. 



