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origin. A very interesting table showing the chemical composition 

 of the ancient igneous rocks of Maryland accompanies this paper. 



With regard to the pegmatites, evidence is presented for the belief 

 that very many of them are eruptive ; though it is not thought that all 

 will be found to have had that origin. The evidence that they are 

 eruptive is based upon the agreement in composition between the 

 granites and the pegmatites, the greater abundance of the latter near 

 granite masses, their independence as regards the character of the 

 rocks they cross, their relations to the adjoining rock, and the fact 

 that as a rule these pegmatites are neither drusy nor symmetrically 

 banded. The fact that in spite of the essential identity between the 

 composition of the pegmatites and the granites there are certain dif- 

 ferences, is interpreted as pointing to somewhat different conditions 

 of formation, in which there was a greater activity of the mineralizing 

 agencies. 



The author agreed closely with De Beaumont, Lehmann, and 

 Brogger in his conception of the process of the origin of these peg- 

 matites. They are interpreted " as the products of the residual, and 

 therefore most acid, portion of a granite magma highly charged with 

 water and other mineralizing agents, in a state intermediate between 

 fusion and solution, interjected into fissures and there crystallized in 

 very coarse-grained aggregates, not necessarily throug):i any great 

 slowness of this process, but rather in virtue of the aid to crystalliza- 

 tion afforded by the abundance of mineralizers present." 



H. F. Bain. 



Sketch of the Geology of the San Francisco Peninsula, by Andrew C. 

 Lawson. Fifteenth Ann. Rep. U. S. Geol. Surv., pp. 399- 

 476. Pis. V-XII. 



This paper is a valuable contribution to the literature of the Pacific 

 coast. The area considered lies between the Pacific Ocean and San 

 Francisco Bay, and extends from the Golden Gate southward about 

 twenty-one miles. 



The work done reveals seven formations which, in their geological 

 order, are : (i) Crystalline limestone; (2) Montara granite ; (3) The 

 Franciscan series ; (4) Sandstone of Tejon(?)age; (5) The Monterey 

 series ; (6) The Merced series ; (7) The Terrace formations. 



The Montara granite is exposed along the Pacific shore about one 



