628 FRANK D. ADAMS 



rocks occurring elsewhere, as for instance the trap granulites of the 

 Saxon Granulitgebirge or the amphibohtes of the crystalHne complex 

 of certain portions of the Alps, whose origin remains in doubt while 

 that of the rocks with which they are associated has been definitely 

 determined. 



As the result of a very careful examination, it has been possible 

 to prove conclusively that in this area the amphibohtes have originated 

 in three entirely different ways, the resulting rocks, although of such 

 diverse origin, often being identical in appearance and composition. 

 This remarkable convergence of type, whereby rocks of widely dif- 

 ferent origin come to assume identity of character, explains the 

 difficulty which has been experienced up to the present time in 

 arriving at a satisfactory conclusion concerning their genetic relations. 

 These three ways are: (a) By the metamorphism and recrystalliza- 

 tion of impure calcareous sediments; (b) By the alteration of basic 

 dykes and similar igneous intrusions; and (c) By the contact action 

 of the granite bathyliths on the limestones through which they cut. 

 The question of the origin of these amphibolites is discussed else- 

 where.^ 



THICKNESS OF THE GRENVILLE SERIES IN THE HALIBURTON- 

 BANCROFT AREA 



While in most parts of this area the Grenville series is so torn to 

 pieces by igneous intrusions that no development of it can be found 

 sufhciently continuous to enable its thickness to be measured, there 

 are in certain parts of the area developments where these intrusions 

 are distinctly subordinate and in which such measurements can be 

 made with at least the same degree of accuracy as in the case of any 

 other pre-Cambrian series. 



One such district is that where the four townships of Anstruther, 

 Burleigh, Chandos, and Methuen meet. Here a well-defined syn- 

 clinal is succeeded to the east by an anticlinal, and the following 

 succession of strata, which however does not represent a complete 

 section through the Grenville series of this area, is expressed in 

 descending order (Burleigh-Chandos section). 



I Journal of Geology, Vol. XVII, No. i. 



