BY LEO A. COTTON. 755 



-experimentally established this result by torsion-experiments 

 upon glass rods. They have also proved that the planes of 

 fracture make angles of about 45° with the axis of torsion. In 

 extreme cases, where great deformation took place before rupture 

 was effected, the planes of fracture made angles as large as 60° 

 with the axis of torsion. Daubree has further shown that simple 

 pressure on a body of a somewhat plastic nature, comparable to 

 a rock-mass, gives rise to fracture-planes making 45° with the 

 line of pressure. 



As, then, in the area considered, the main fracture-system is 

 about N. 39' E., the direction of pressure or axis of torsion must 

 have been along a line bearing about N. 84° E. 



In a body which is neither uniform, nor capable of great defor- 

 mation before rupture, fractures may occur parallel to the direction 

 of pressure. Near the north-west corner of Portion 214, Parish 

 of Cope's Creek, County of Hardinge, an intrusion of the "Acid 

 Granite" into the slates has been intersected by a series of faults. 

 As the granite is the intruding body, and the slate the resisting 

 one, we may assume that the slate has remained stationary, and 

 that the granite has moved. This gives the direction of the 

 thrust on the granite. The intrusion is that previously referred 

 to in text-fig. 1. 



The creek has removed the soil, and the section is beautifully 

 exposed. The intrusion took place as a long, narrow, approxi- 

 mately rectangular tongue, narrowest where it joins the granite- 

 mass. Here it is only 9 inches in width, whereas at its extremity 

 remote from the granite, it attains a width of 2 feet. This end 

 abuts rather sharply against the slate, and has probably been 

 faulted. Any continuation that may exist to the south is covered 

 by alluvial. The direction of the intrusive tongue is S. 20° E., 

 while a series of faults varying from N. 60° E., to N. 80° E. have 

 thrown the tongue to the west. This is approximately the 

 direction(84°) deduced from the axis of pressure or torsion which 

 has acted on the Elsmore mass. 



It is noteworthy that the main direction of fracture(N.39-4°E.) 

 observed for the Elsmore granite-mass, corresponds very closely 



