Morgan. — Water in Rock-magmas. 405 



water present is pln^sically a gas, either held in sohition by pressure alone 

 or actually segregated in the form of gas-bubbles. 



2. The presence of water induces or aids the differentiation of a magma 

 into two or more layers differing in chemical composition. 



3. The presence or absence of water has much to do with the distribu- 

 tion and formation of magma in the upper layers of the earth's crust. 



4. The escajie of water, as well as cooling, is a determining cause in the 

 consolidation of aqueo-igneous magmas. 



5. Some plutonic rocks, more especially granites, may represent sedi- 

 mentary rocks fused by aqueo-igneous action. 



6. Differentiation in consolidating aqueo-igneous magma is partly ex- 

 plained . 



7. A fairly efficient h}^othesis of volcanic action and magmatic differen- 

 tiation in connection therewith can be evolved. 



8. Hot springs may precede as well as follow a period of volcanic 

 activity. In the latter case their water is probably not magmatic. 



By varying the permissible assumptions in connection with water in 

 rock-magmas a great variety of hypothetical results may be obtained. The 

 necessity for eliminating false assumptions by such experimental research 

 as is possible therefore becomes obvious. Though experimental work in 

 geo-physics is difficult and expensive, and in some respects can never be 

 conclusive, much may be done in a properly equipped laboratory. Hence 

 there is reason for hoping that in a few years' time our knowledge of the 

 earth's interior may be greatly increased, and placed on a much more 

 satisfactory basis. 



Literature. 



1. Posepny, F. ; Vogt, J. H. L. ; Kemp, J. P.; and others: "Genesis 



of Ore-deposits.' Published by American Institute of Mining 

 Engineers. Second edition. New York, 1902. 



2. Preston, Thomas : " Theory of Heat." Second edition, revised bv 



J. Rogerson Cotter, 1904. 



3. Chamberlin, T. C, and Salisbury, R. D. : " Geologv." Vol. 1, first 



edition, 1905. 



4. Arrhenius, Svante : " Worlds in the Making." Translated by H Barus 



1908. 



5. Journal of Chemical Society, December, 1909. Abstracts, ii, p. 985. 



Reference to Andreas Smits and J. P. Wuite in Proc. k. Akad. 

 Wetensch. Amsterdam, xii, 1909, pp. 244-57. 



6. Harker, Alfred : " The Natural History of Igneous Rocks." 1909. 



7. Moir, James : Inaugural Address in Journal of the Chemical, Metal- 



lurgical, and Mining Society of South Africa, vol. 11, No 1 July 

 1910. 



8. Clarke, F. W. : " Data of Geo-chemistry." Second edition U S G S 



Bulletin No. 491, 1911. 



9. Brun, Albert : " Recherches sur I'Exhalaison Volcanique." Geneva, 



1911. See also " The New Vulcanology," by E. B. Bailey in GeoL 

 Mag., dec. 5, vol. 8, 1911, pp. 268-73 and 311-16 ; and " Brun's 

 New Data on Vulcanism," by Alex. N. Winchell, in Economic Geology, 

 vol. 7, No. 1, January, 1912, pp. 1-14. 

 10. Daly, Reginald A.: "The Nature of Volcanic Action." Proc. Amei. 

 Acad. Arts and Sci., vol. 47, No. 3, June, 1911, pp. 47-122. Sum- 

 mary m Journal of Geology, vol. 20, No. 5, July- Aug., 1912, pp. 471-75. 



