R. A. Daly — Abyssal Igneous Injection. 199 



somewhat compressible but almost perfectly elastic, the same 

 reasoning may possibly apply to an anhydrous substratum.* 

 Again, the recently developed view that the great nucleal 

 mass of the earth is composed of true gas immensely com- 

 pressed, must also be reckoned with in the attempt to prove- 

 rigidity by the oceanic tides. 



Purpose of the present paper ; acknowledgments. — While 

 the question as to how much of the earth is fluid is now quite 

 open, the hypothesis of crust and fluid substratum has many 

 special points of advantage. Many writers have shown how it 

 agrees with essential observations on the structure and history 

 of the rocks accessible at the earth's surface. It appears, how- 

 ever, that important consequences of the hypothesis, conse- 

 quences involved in the correlation of subsurface tensions 

 with igneous intrusion, surface deformation and mountain- 

 building, have, so far as known to the writer, never been 

 systematically deduced. This paper is intended to form a 

 brief and but qualitative treatment of the subject.f 



The writer has pleasure in acknowledging the great courtesy 

 of Professor F. D. Adams, who afforded much help in discuss- 

 ing such physical constants of rocks as form data required in 

 the following hypothesis. Special thanks are due to Dr. A. C. 

 Lane, who has, by correspondence, discussed anew the relation 

 between subsurface tensions and the gases evolved from the 

 earth's interior; also to the Rev. O. Fisher and to Professor 

 L. V. Pirsson, who, similarly by correspondence, have offered 

 valued suggestions. But, in justice to these investigators, it 

 may be added that they should be clearly absolved from all 

 responsibility in launching this new hypothesis on the sea of 

 discussion, which has borne whole fleets of older hypotheses of 

 mountain-building, has sunk many of them, and still floats 

 the more or less battered but more seaworthy hypotheses. 

 The ribs of this new vessel are few — assumptions which them- 

 selves may long have to remain in the workshop of geological 

 opinion ; to these the planks of argument have been fastened 

 and again there is a chance that the vessel is neither tight nor 

 trim. Each postulate and almost every argument of the 

 hypothesis well merits a whole article to itself, but their elabo- 

 ration or destruction may wisely be left to more skilful hands. 

 This paper is little more than the barest statement of a sugges- 

 tion which is offered expressly for criticism. The necessary 

 brevity of treatment forbids that constant, explicit reference 



*Lord Kelvin states that crystals and glasses probably possess elasticity of 

 volume "to perfection" — art. "Elasticity" in the Encyclopaedia Britan- 

 nica, 3d paragraph. 



f The relative merits of the planetesimal and nebular hypothesis of the 

 earth's origin are not discussed, but the older hypothesis may be regarded as 

 basal to the argument. 



