﻿522 DED0L0MITIZATI0N IN THE MARBLE OF POET SHEPSTONE. [Nov. 1 9 1 0, 



formed at the expense of the dolomite and confined to the imme- 

 diate vicinity of the blocks, although the dolomite everywhere 

 else was converted to a coarsely crystalline marble under the in- 

 fluence of a later granite invasion — and, however novel the Authors' 

 interpretation might be, it was the simplest explanation of the 

 facts. Dr. Evans's view that the granite fragments had been 

 formed by the breaking-up of an intrusive vein in the dolomite 

 during earth-movements, all trace of which had been obliterated 

 by a later metamorphism, was ingenious and possibly correct. 

 Even if correct, it would still have to be admitted that chemical 

 interaction had taken place between the fragments of the earlier 

 granite and the dolomite, under the influence of the intense meta- 

 morphism of the later granite-invasion, since each fragment was 

 completely surrounded by a reaction-rim. The speaker further 

 drew attention to the fact that the two granites belonged to 

 distinctly different petrographical provinces. 



In reply to a question put by Dr. Johnston-Lavis, he said that 

 the interior of the granite blocks showed no zonal arrangements of 

 minerals. Mr. Crook's criticism of the high-temperature question 

 was more relevant, and would be considered by the Authors ; but 

 it was immaterial to the main issue whether the metamorphism 

 of the dolomite took place at a high, or at a low, temperature. 





