698 CLARENCE N. FENNER 



in which he describes certain contact rocks formed by the action of 

 a granite bathohth upon schists: 



The characteristic of the contact phenomena of this type consists essen- 

 tially in the addition of volatile or transportable materials, emanating from the 

 magma and modifying generally in a manner more or less profound the chemical 

 and mineralogical constitution of the sediments traversed 



In the regions which form the object of this study, and in many others, the 

 disposition of the sedimentary beds in relation to the granite, the existence in 

 the midst of the latter of sedimentary fragments which, in spite of their trans- 

 formation, have preserved the same orientation as the peripheral schists and 

 limestones to which they belong, finally the absence of important dislocations 

 at the immediate contacts, tend to show that the granitic magma has been 

 brought to its position in a slow and progressive fashion by imbibition and dis- 

 solution of the sediments for which it has been substituted. 



In proportion as the granitic magma appeared in the sedimentary beds 

 it was preceded and accompanied there by its cortege of transforming emana- 

 tions, and what it had to dissolve to make place for itself was no longer normal 

 sediments, but transfused rocks, transformed or in process of transformation 

 by fixation of the emanations which had gone out from its own mass. 



The most intense modifications undergone by the schists metamorphosed 

 into leptynolites consist essentially in the development of a large quantity of 

 feldspars, quartz, biotite, etc. The limit toward which these leptynolites, 

 which are often comparable from a mineralogical standpoint with gneisses, 

 tend is the mineralogical composition of granite itself. 



In a recent article Sederholm' describes contact-effects of a 

 rapakivi granite upon older hornblende-schists, with introduction 

 of typical minerals from the rapakivi. He is able to trace out the 

 transitional changes in the minerals of the schist by absorption of 

 material from the granite. ''Microscopically as well as macro- 

 scopically it is shown, therefore, that the whole schist-mass has been 

 permeable for gases and juices (Safte) which have gone out of the 

 granite magma, as well as for the magma itself in further progress 

 of change. This contact would have convinced even the most 

 zealous anti-injectionists. " 



The ideas which are formulated in these quotations have met 

 with opposition from some geologists, but the objections seem to 

 be based partly upon a misconception. The advocates of the 



^ J. J. Sederholm, "Ueber ptygmatische Faltungen," Neu. Jb., XXXVI (Septem- 

 ber, 1913), Beilage-Band, p. 491. 



