260 A. C. LANE — GEOLOGIC ACTIVITY OF THE EARTH's GASES. 



may not be out of place. I claim no such originality. It is true the 

 main outlines of this theory of igneous phenomena came into my con- 

 sciousness as the result apparently of my own thinking when, in college 

 days, I was convinced by Darwin's paper in Thomson's and Tait's 

 " Natural Philosophy "that the earth must be regarded as rigid ; but in 

 the intervening years I found in reading along the suggested lines that 

 almost every point had been thought out before me. Meanwhile the 

 facts have been marshalling themselves in my mind around this theory, 

 and in this connection I must acknowledge obligation to Neumayr's 

 " Erdgeschichte " and to writings and conversations with numerous 

 teachers and friends. 



Nearly five years ago there was published Reyer's " Theorische 

 Geologic," which occupies very much the same position in very many 

 points as this paper. Directly to this book I owe but little. In fact, 

 the argument of this paper was written and shown to Dr Wadsworth 

 many months ago and before I had seen the book, to which I would 

 refer, however, as a magazine of facts in support of the ideas here 

 advanced. He also gives references to previous authors to whom the 

 first thoughts are really due. 



I have said little about these ideas during these ten years, partly for 

 fear of hardening them by controversy from a hypothesis to a theory in 

 ni}^ mind and partly because I was bothered to see how the fissures 

 which the theory requires could penetrate the lower regions under the 

 hydrostatic pressure and plasticity which there exist. The conception 

 that the occluded gases might counteract this hydrostatic pressure is the 

 most original point in the paper, so far as my reading has yet gone. 

 Minor divergencies in the point of view from previous writers may also 

 be remarked, as might be expected in largely independent work, and I 

 flatter myself that I have marshalled several lines of facts in support of 

 the theory whose bearing in that direction has hitherto escaped notice. 

 The interwelding of Tschermak's theory as to the escape of occluded 

 gases with Durocher's theory, slightly modified, as to the composition 

 of the earth seems to me to add mutual strength. The parallelism be- 

 tween volcanic and blast-furnace reactions, already remarked by Bell, 

 thus developed will lead to a fruitful line of inquiry. The tendency to 

 obliterate the line between plutonic and volcanic rocks may be checked, 

 and the harmonizing of igneous phenomena with those which point to a 

 solid earth will be another stumbling block removed. 



In order to reduce to a minimum the labor and library required to 

 verify the facts referred to, I have just gone over the paper and Avhenever 

 possible changed the references to the 1893 edition of Geikie's Text-book 

 of Geology, just out, in which further details and references to the origi- 

 nal papers may be found. 



