Petro graphical Relations of Laurentian Limestones. 37 



widening zone of metamorphosed limestone. He says J 

 " La mise en place du granite s'est effectuee par dissolution 

 graduelle des roches sedimentaires dont il occupe la 

 place ". " L'evidence 3 de la transformation du granite par 

 dissolution du calcaire est complete ". In a thin section 

 from south-eastern New York, described by Williams 3 

 and already mentioned, where a narrow dyke cuts lime- 

 stone, the nature of the igneous rock is considerably 

 modified and can be seen to have become enriched in lime 

 from the limestone, while this latter, on the other hand, 

 has derived silica, alumina, iron, etc., from the material of 

 the dyke. 



Of so-called intrusions in the granite, Lacroix says : 4 

 " Je considere clone, toutes ces couches metamorphiques 

 isolees aujourdhui au millieu du granite comme le residue 

 non digere des assises sedimentaires dont le granite a 

 pris la place." This may have an important bearing on 

 the gray gneisses or quartz diorites which occur through- 

 out these granites in Ontario. 



If these views are correct, they would serve to explain 

 nearly every phenomenon observed in this occurrence in 

 Central Ontario. But the great weakness in them is the lack 

 of chemical proof. Till that is at hand, it may be said that 

 " while the transfusion of a certain amount of material 

 into the limestones along the immediate contact of the 

 intrusions, and also a solution of the limestones to a 

 limited extent in certain cases seems highly probable, the 

 wholesale transformation of limestone into diorite, or of 

 shale into gneiss and granite — is as yet very far, indeed, 

 from being proved." 5 It may be said in their favor 

 however, that as the study of this area has gone on, these 

 views have come to appear to the writer, at least less and 

 less irrational. 



1. ibid., p. 3. 2. ibid., p. 60. 3. loc. cit., p. 267. 



4. Livret Guide, p. 15, see Adams, " The Excursion to the Pyrenees," loc. cit., p. 42. 



5. Adams, F. D., " The Excursion to the Pyrenees," loc. cit., p. 46. 



