A HISTORY OF SCIENCE 



sive force of the lower strata of dilated crystalline 

 matter, was augmented, it acted upon the upper and 

 more liquefied strata. These being prevented from 

 yielding outwardly by the tenacity and weight of the 

 solid involucrum of precipitated and sedimental de- 

 posits which overspread them, sustained a pressure out 

 of proportion to their expansive force, and were in 

 consequence proportionately condensed, and by the 

 continuance of the process, where the overlying strata 

 were sufficiently resistant, finally consolidated. 



"This process of consolidation must have pro- 

 gressed from above downward, with the increase of the 

 expansive force in the lower strata, commencing from 

 the upper surface, which, its temperature being lowest, 

 offered the least resistance to the force of compres- 

 sion. 



" By this process the upper zone of crystalline matter, 

 which had intumesced so far as to allow of the escape 

 of its aqueous vapor and of much of its mica and 

 quartz, was resolidified, the component crystals ar- 

 ranging themselves in planes perpendicular to the 

 direction of the pressure by which the mass was 

 consolidated that is, to the radius of the globe. 

 The gneiss formation, as already observed, was the 

 result. 



" The inferior zone of barely disintegrated granite, 

 from which only a part of the steam and quartz and 

 none of the mica had escaped, reconsolidated in a con- 

 fused or granitoidal manner; but exhibits marks of the 

 process it had undergone in its broken crystals of fel- 

 spar and mica, its rounded and superficially dissolved 

 grains of quartz, its imbedded fragments (broken from 



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