80 Notices of Memoirs Segregation of Sulphide Ores. 



earth reside in the earth itself, and that " the earth is not merely 

 an inert mass cooling in space." ^ 



Our conception of the geologic potentialities of matter has been 

 marvellously widened by the recent discoveries. How these dis- 

 coveries may affect our views of the interaction of matters as 

 explaining geological changes remains to be decided when the new 

 methods are established on a firm basis, of which there seems to be 

 an early prospect. 



ITOTIGiES OIF n^/CIBIMIOIIEaS, lETC. 



Abstracts of Papers read before Section C (Geology), British Association : 

 South Africa, 1905. 



I. — On the Marginal Phenomena op Granite Domes. By 

 Professor Grenville A. J. Cole. 



IN examining the gneisses of the counties of Donegal and Tyrone, 

 which have been in part regarded as sheared Arcbtean masses, 

 the author was led to conclude that the main structures are due to 

 igneous flow, and that the most marked gneissic structure occurs 

 where previously foliated sedimentary and igneous material has been 

 incorporated with an invading granite. The patches of foliated 

 gneiss in the granites of Donegal are thus remnants of considerable 

 masses of older rock that have been absorbed ; and the phenomenon 

 of banded gneiss arises characteristically as a marginal feature of 

 granite domes. Foliation is found in surrounding masses parallel 

 to that in the granite, and at the same time parallel to the surface 

 of junction, for the simple reason that the granite has picked off, 

 leaf by leaf, the layers of foliated rock against which it rose. The 

 author thus ranges himself with those who ascribe the most profound 

 metamorphism to igneous rather than to dynamic action, and 

 ventures to suggest that similar conclusions may be drawn from the 

 rocks of the Malmesbury series in the west of Cape Colony, where 

 a commingling of rocks appears to have taken place during a period 

 of subterranean flow. 



II. — Magmatic Segregation of Sulphide Ores. By Dr. A. P. 



Coleman. 



HE formation of ore bodies by magmatic segregation in eruptive 



T 



titaniferous iron ores, but the formation of sulphide ore bodies in 

 this way has been disputed by many geologists. The pyrrhotite 

 ores of nickel in Norway were first recognised by Professor Vogt as 

 having this origin ; and his theory has been applied to the Sudbury 

 nickel ores by various geologists, and opposed by others. The 

 recent complete mapping of the eruptive sheet, with which the 

 Sudbury ore bodies are all connected, proves that they are really 



1 "Evolution of Earth Structure," p. 28. 



