142 Barrell — Growth of Knowledge of Earth Structure, 



Thus between mashing, injection, and assimilation the 

 genetic relationships of a batholith to its surroundings 

 are in many instances obscure. Nevertheless, attention 

 to the larger relations shows that the molten magma orig- 

 inated at great depths in the earth's crust, far below the 

 bottoms of geosynclines, and consists of primary igneous 

 material, not of fused sediments. From those depths it 

 has ascended by various processes into the outer crust, 

 where it crystallized into granite masses, to be later 

 exposed by erosion. The amount of material which can 

 be dissolved and assimilated must be small in compari- 

 son with the whole body of the magma. The original 

 composition of the magma was probably basic, nearer 

 that of a basalt than that of a granite. Differentiation 

 of the molten mass is thought to cause the upper and 

 lower parts of the chamber to become unlike, the lighter 

 and more acidic portion giving rise to the great bodies of 

 granite. With the exception of certain border zones the 

 whole, however, is regarded as igneous rock risen from 

 the depths. 



The complex border relations, but more particularly 

 certain academic hypotheses, led to a period of misunder- 

 standing and retrogression in regard to the nature of 

 granites. It constitutes an interesting illustration of 

 the possibility of a wrong theory leading interpretation 

 astray, chiefly through the magnification of minor into 

 major factors. This history illustrates the dangers of 

 qualitative science as compared to quantitative, of a 

 single hypothesis as matched against the method of mul- 

 tiple working hypothesis. This flux of opinion in regard 

 to the nature of granites may be traced through the vol- 

 umes of the Journal. 



E. Hitchcock in 1824 (6, 12) noted that in places gran- 

 ite appeared bedded, but in other places existed in veins 

 which cut obliquely across the strata. Silliman, although 

 careful not to deny the aqueous origin of some basalts, 

 yet held that the field evidence of New England indicates 

 for that region the igneous or Huttonian origin of trap 

 and granite (7, 238, 1824). 



In 1832 the following article by Hitchcock appeared in 

 the Journal (22, 1, 70) : 



Report on the Geology of Massachusetts ; examined under the 

 direction of the Government of that State, during the years 



