468 Notices of Memoirs — British Association — 



conjunction with the water shut up in or circulating through a rock. 

 If we understand how these factors operate and produce the results 

 we see in cases of contact - metamorphism, we shall not fail to 

 understand their action in a case of dynamic-metamorphism. 



These observations also apply to regional metamorphism ; that 

 is to say, to metamorphism produced in rocks at great depth, by 

 being brought within the influence of the interior heat of the earth. 

 The action of heat in increasing molecular motion and kinetic energy 

 is well understood nowadays, and so long as we get heat it seems 

 to me immaterial how heat is generated in rocks subject to meta- 

 morphic action. 



In the above sketch I have intentionally omitted to enter into 

 the details of chemical action that has brought about individual 

 cases of metamorphic change. Volumes would be required to do 

 justice to so complex a subject, and the details would, in an opening 

 address, be out of place. 



In conclusion, I have, I trust, shown how important a part water 

 plays as an agent of metamorphism, not only at and near the surface 

 of the earth, but at plutonic depths. We have seen that the molten 

 granite of the Satlej Valley, which was given as an illustration of 

 a fluid igneous magma, contained a considerable proportion of water 

 held in solution at considerably above red heat, and that the fluidity 

 of the magma was due to its presence. We also saw that the great 

 heat to which the magma was raised increased the potential energy 

 of the contained water; a relief of pressure then opened the way 

 for the intrusion of the molten magma into neighbouring rocks. 

 We also saw that this water was I'endered by heat a powerful 

 solvent, and that it carried with it into the adjoining rocks the 

 mineral matter of the granite in solution. We also saw that heat 

 increased the porosity of minerals, facilitated the passage of liquids 

 laden with mineral matter through their pores, and increased the 

 potency of chemical action. 



II. — List of Titles of Papers read before the British 

 Association for the Advancement of Science, Belfast, 

 Sept. 10-17, 1902, in the Geological and other Sections 

 bearing upon Geology. 



Section A (Mathematical and Physical Science). 



Br. Isaac Roberts, F.B.S. — Illustrations obtained by Photography of 



the Evolution of Stellar Systems. 

 Major S. G. Burrard, B.M—On the Figure of the Earth. 

 J. Milne, F.B.S. — Observations on Earthquakes. 

 Report of the Seismological Committee. 



Section B (Chemistry). 

 Dr. J. H. Gladstone. — On Fluorescent and Phosphorescent Diamonds. 



Section C (Geology). 

 Lieut.-Gen. C. A. McMahon, F.B.S., F.G.S., Presidenf.— President's 

 Address — Eock Metamorphism. (See p. 458.) 



