78 



large boulders of granite in the conglomerate, which forms 

 part of the highest outcrops of the Lower Huronian 

 (Cobalt series), have been carried so far from their parent 

 masses. These large boulders are found over much of the 

 district, and there are now no outcrops of granite in the 

 neighborhood of many of them. ... In the present 

 state of our knowledge we have little warrant for claiming 

 that the granite boulders, often two or three feet or more 

 in diameter and distant a couple of miles from exposures 

 of the rock, indicate glacial conditions during Lower 

 Huronian times, although we have no proof to the 

 contrary."* 



A couple of years after this report was published Dr. 

 A. P. Coleman, while on a visit to the Trethewey mine, dis- 

 covered striated boulders in the conglomerate in an outcrop 

 on this propertyf that have all the characteristics of those 

 which are found in glacial deposits. Hence, Dr. Coleman 

 and other writers have decided that a certain part, at least, 

 of the conglomerate of the Cobalt series is of glacial origin. 



In the opinion of the present writer more evidence is 

 required before the glacial origin can be accepted. Although 

 for many years conglomerates similar to those of Cobalt 

 have been studied over a vast extent of territory in northern 

 Ontario, no glaciated surface on the rocks underlying this 

 conglomerate has been discovered. During the last few 

 years several workers in the Cobalt and surrounding areas 

 have diligently searched for such a surface, but without 

 success. The underlying rocks present, characteristically, 

 a weathered surface, there being no sharp line of division 

 between the underlying, undecomposed, or non-disintegrated, 

 rock and the overlying fragmental rock. The glacial origin 

 of the Cobalt conglomerate cannot therefore be proved so 

 clearly as it can for similar rocks in other parts of the 

 world. The Dwyka of South Africa, for example, rests on 

 rocks that frequently show undoubted evidence of having 

 been smoothed by glaciers. Opportunities for observing 

 contacts at Cobalt are, however, being constantly enlarged 



*Fourteenth Report, Bureau of Mines, Ontario, Part II., page 43. 

 fAm. Jr. Science, 'March, 1907. Journal of Geology, February- 

 March, 1908. 



