196 HOLLAND: CIIAHNOCKITE SERIES. 



along certain lines, but may be observed more or less distinctly 

 throughout the rocks. Where it occurs there is neither saussurite nor 

 uralite— although the granulation of the pyroxene may be carried 

 so far that only the smallest remnants of the original individuals 

 remain." From this, as part of the evidence, he concludes that 

 " these movements probably took place when the rock was still so far 

 beneath the surface of the earth and so weighted down by the 

 overlying rocks that breaking and shearing with the movement 

 of the resulting masses was impossible. Such a motion would 

 present certain resemblances to that of a very tough pasty mass 



... while the rock was still very hot and perhaps even near 



its melting point. This would explain why pyroxene, which, 

 according to the experiments of Fouque and Michel-Levy, represents 

 the stable form at a high temperature, is not changed into amphibole 

 which represents the more stable form at a low temperature. 1 " 



All these remarks are applicable too to the charnockite 

 series, and with regard to the last point it is not unlikely that the 

 great prevalence of pyroxenic rocks in these old protaxes, like 

 Canada and Madras, where denudation has proceeded uninterruptedly 

 for such long ages, is due to the exposure of relatively low portions 

 of the earth's crust, lower portions comparatively than those which 

 have been protected by sedimentary coats, and low enough to 

 permit such a regional rise of temperature that the pyroxenes, for 

 instance, are crushed without amphibolization. 



The prevalence of garnets in some members of the charnoc- 

 kite series which show no signs of dynamo-metamorphism, suggests 

 that although the pyroxene is the stable form near fusion point 

 and hornblende the stable form of the same compound at low 

 temperatures, there is an intermediate, but high, temperature, 

 short of fusion, at which either hornblende or pyroxene breaks 



1 Adams. " Report on the Geology of a portion of the Laurentian area lying to the nortli 

 of the Island of Montreal." Annual Report of the Gejl. Surv. Canada, Vol. VIII (1896), 

 part J, pp. 114 and 115. There are many interesting points of resemblance between the old 

 Canadian protaxis which has been exposed to continuous denudation since Potsdam days and 

 that of Madras. 



( 78 ) 



