﻿ANNIVERSARY ADDRESS OF THE PRESIDENT. 



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operation was, with greater probability, the slow continuous effect of 

 thousands of years of chemical action under enormous pressure. 



M. Delesse has very recently presented us with another work in 

 which the larger subject is treated of with great minuteness of detail, 

 and in which he has brought to bear his extensive observations, his 

 mineralogical knowledge, and his skill and experience in chemical 

 analysis. He has been so obliging as to send me an unpublished 

 copy of his memoir, which, consisting of 90 quarto pages, will form 

 a part of a forthcoming volume of the ' Memoires de l'Institut de 

 France.' In this work he by no means confines the term metamor- 

 phism to those rocks to which it was originally applied by Lyell, 

 and to which it is restricted by many geologists, but gives it a very 

 wide range. He says at the very outset, " Toutes les roches qui 

 entrent dans la composition de l'ecorce terrestre ont pu etre modifiees 

 par le metamorphisme general " (p. 129) ; that " il est bien con- 

 state maintenant que les roches metamorphiques se sont formees k 

 toutes les epoques geologiques " (p. 152). He speaks of " roches 

 metamorphiques appartenant a tous les terrains, depuis le silurien 

 jusqu'au nummuhtique" (p. 155). He considers that the for- 

 mation of coal in all its varieties, from lignite to anthracite, is the 

 result of general metamorphism : " Le metamorphisme general subi 

 par les combustibles est identique a celui qui est eprouve au contact 

 de roches non-volcaniques " (p. 160). It is evident, therefore, that 

 metamorphic action, in the sense in which it is used by M. Delesse 

 in this memoir, becomes nothing more than a general term for that 

 agency or variety of agencies by which mineral substances have un- 

 dergone alterations from their original state throughout all geological 

 periods, and is the abandonment of a very convenient technical desig- 

 nation for a particular class of rocks — those inferior basic rocks which 

 have been held to have been for the most part transformed from a 

 prior condition of sedimentary deposits. 



On the 30th of last June, the Academy of Sciences of Paris awarded 

 to M. Daubree the Bordin Prize for an essay entitled " Etudes et 

 Experiences synthetiques sur le Metamorphisme et sur la formation 

 des roches cristallines," which has since been published. He com- 

 mences with the following remarks : — " One of the most important 

 questions which geology is called upon to solve, is to settle the parts 

 in the formation of the solid envelopment of the globe which are to 

 be ascribed respectively to aqueous and igneous action. Although it 

 has been long debated, it has as yet received no definite solution ; it 

 has even become complicated, since by a more rigorous examination 

 of different rocks we have discovered evidence of a twofold origin. 

 Was it at the very moment of their formation that these ambiguous 

 rocks received this double character, or was the one consecutive on 

 the other ? and, in the latter case, how can we account for such a 

 succession of effects ? These are subjects the study of which con- 

 stitutes what in their more extended and general sense we term 

 metamorphism." He gives a historical sketch of the gradual de- 

 velopment of those observations on the structure of rocks by some of 

 his predecessors which have led the way to the views now generally 



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