168 A CENTURY OF SCIENCE 



up through Paleozoic time until gradual subsidence had 

 permitted it to be buried beneath 30,000 feet of sedi- 

 ments. 5 



It may seem to the present day reader that such a mis- 

 interpretation, doing violence to fundamental geologic 

 knowledge as now recognized, was inexcusable; but in 

 the light of the history of geology as here detailed it is 

 seen to have been the interpretation natural to that time. 

 It is true that a careful examination of the facts of that 

 very field would have proved the post-Paleozoic and in- 

 trusive nature of that great granite body now known 

 as the Little Cottonwood batholith, but Emmons has 

 explained the rapid and partial nature of the observa- 

 tions which they were compelled to make in order to keep 

 up to their schedule of progress (16, 139, 1903). 



Whitney had found some years earlier that the gran- 

 ites of the Sierra Nevada were igneous rocks intrusive 

 into the Triassic and Jurassic strata. The Lake Supe- 

 rior geologists began to show in the eighties that granite 

 was there an intrusive igneous rock. R. D. Irving and 

 "Wadsworth noted these relations. Lawson in 1887 

 pointed out emphatically (33, 473) that the granites of 

 the Rainy Lake region, although basal, were younger 

 than the schists which lay above them. The granite- 

 gneisses he held were of clearly the same igneous origin 

 as the granites and neither gave any field evidence of 

 being fused and displaced sediments. From this time 

 forward the truly igneous nature of granite became 

 increasingly accepted until now the notion of its being 

 made of sedimentary rocks softened and recrystallized by 

 the rise of the isogeotherms through deep burial is as 

 obsolete as the still older doctrine of the Neptunists that 

 granite was laid down as a crystalline precipitate on the 

 floor of the primitive ocean. 



The recognition of the truly igneous nature of granites 

 has been followed in the present generation by a series 

 of studies on their structural relations and mode of 

 genesis. A number of important initial articles on vari- 

 ous aspects of structure and contact relations have 

 appeared in the Journal, but this sketch of the history of 

 the subject may well stop with the introduction to this 

 modern period. 



