282 R. T. HILL PELE AND THE WINDWARD ARCHIPELAGO 



the earth's interior. As a result, and opposed to the crustal theories of 

 origin of volcanoes* these new ideas are focusing around the belief that 

 volcanoes and their products are manifestations of forces and material 

 existing within the interior of the earth itself, held by some to be neither 

 liquid nor solid, but gaseous, and which by expansion has the power to 

 ascend through the earth's crust and to produce by differentiation under 

 different physical conditions of pressure and cooling all the known sub- 

 stances accompanying volcanic phenomena — rocks, metals, gases, and 

 water. 



• These theories have recently been strengthened by four distinct lines 

 of research, to wit, physical studies bearing upon the conditions of the 

 earth's interior; practical researches in deep mines by various eminent 

 geologists in relations to the origin of ore deposits; Professor Suess' conclu- 

 sions as to the interior origin of atmospheric waters; Sir William Ramsey's 

 investigation of gases exhaled by the earth. The writer's own personal 

 unpublished investigations of the geologic history of the West Indian 

 and Central American and Mexican volcanoes have at least led him to 

 believe that the interior theories are much nearer the true explanation 

 of vulcanism than those of the crustalists. 



In America interest as to the nature of the earth's interior has been 

 principally kept alive by a practical, rather than the merely theoretical, 

 line of research. Mining methods have advanced beyond the old axiom 

 of " follow the ore " to the scientific stage where the modern miner em- 

 ploys geologists to explain and " hunt the ore " by studying laws of 

 origin and occurrence of mineral deposits. The widespread scientific 

 study of the origin of ore deposits has resulted in views concerning the 

 earth's interior far in advance of those maintained by the purely aca- 

 demic geologist. Men like Kemp, Lindgren, Weed, familiar with deep 

 mines as well as theoretical geology, whose researches the writer could 

 largety supplement by his personal observations of the great mines, 

 realized the intimate relation of metallic ore bodies to the great interior 

 processes of the earth. 



Arrhenius* theory of a gaseous center. — In a volume published by the 

 Institute of Mining Engineers on the subject of ore deposits a few years 

 ago Vogtf quoted some paragraphs from the writings of Professor Arr- 

 henius, the eminent Swedish physicist, who presented for the first time 

 in this country an intelligible hypothesis of the conditions of the earth's 

 interior and its contributions to the crust, which alike satisfied the re- 



* Even the crustalis-ts like Dana admit that "igneous action has its origin almost exclusively 

 within the earth's interior," p. 556, while it is generally acknowledged that deep-seated rocks on 

 account of their high temperature are in a potentially plastic or even gaseous condition, which 

 may become plastic on the relief of pressure. 



f Transactions American Institute of Mining Engineers, vol. 18. 



