90 The Ohio Journal of Science [Vol. XVII, No. 3, 



substance is heavy. With long continued and wide-spread 

 study of vulcanism, seismology, and the igneous and meta- 

 morphic rocks themselves, we ought some day to answer some 

 of the questions asked by the laity, even if we still fail to answer 

 our own interrogations. 



On the question of the nature of the interior of the earth, 

 Chemist, Physicist, Mathematician and Geologist must each 

 work for some time. I confess that we do not yet seem to 

 know how to attack the problem. I think it is certain, however, 

 that much study of vulcanism, diastrophism and seismology 

 for a long time over the whole earth, and of the first two through 

 the remote geologic past, will make great contributions to our 

 interpretative theories of the earth's interior. Physicists and 

 Chemists must help before the problem will yield, and it seems 

 evident, even with these several scientific cohorts in siege, 

 that the secrets will be only slowly and reluctantly surrendered. 



7. With these problems comes that of the origin and nature 

 of both igneous and metamorphic rocks. Three recent enlight- 

 ening books on igneous rocks leave us not far, relatively, from 

 where we were before their authors wrote, and this not because 

 they wrote so little, but because they do not yet get together 

 and because their data are still quite insufficient. Rock and 

 mineral analyses are now on record by the tens of thousands, 

 but there are not enough. Nearly all have come from rocks 

 collected between latitudes 25° and 55^^ North and on but two 

 continents. The rest of the earth has its contribution to make. 



Daly* estimates that the sedimentary rocks, if spread 

 uniformly over the earth, would make a layer one-half mile 

 thick. The metamorphics would probably not be more than 

 two or three times as much. It is assumed then that the rest 

 of the earth to the center is of igneous rocks. "The final 

 philosophy of earth history will therefore be founded on igneous 

 rock geology."! But with essentially all the earth consisting 

 of igneous rocks it is evident that our meager scratching on 

 but 10-15 per cent of the surface of the earth cannot give us 

 more than an introduction to the problem of Igneous Rocks. 

 Daly adds, page 42: "The data for a quantitative study of the 

 visible igneous matter in the earth fall far short of being com- 

 plete enough for the ultimate needs of petrogeny. " And 



*Daly, R. A., Igneous Rocks and their Origin, Page 1. 

 fDaly loc. cit. 



