1898] Pleistocene Geology in Ottawa Valley. 211 



Splendid examples of stossing are numerous, and even where 

 the rock is so weathered that no strise are visible, the rounded 

 and smooth appearance of the north side of exposures, and the 

 abrupt and sharp edges on the south, so characteristic of glacier 

 action, may be seen and often enable us to determine with con- 

 siderable accuracy the direction in which the ice moved. Boulder- 

 clay, boulders, Leda-clay, sand and gravel are also abundant, 

 while the less common phenomena of surface geology, viz. : 

 kames, asar or eskers and moraines are occasionally seen. 



BOULDER-CLAY. 



Till, or boulder-clay has been described as a " firm, tough 

 tenaceous clay which gives evidence of having been subjected to 

 great pressure. Often the accumulation becomes coarser and 

 sandier. Again it may be described as a coarse agglomeration 

 of subangular and angular stones set in a scanty matrix of 

 coarse earthy grit and sand. Sometimes the stones in the till are 

 so numerous that hardly any matrix of clay is visible." It will 

 be seen that the term boulder-clay embraces deposits whose 

 appearance differs widely, but however it may vary in appear- 

 ance and composition it can ususlly be recognized by the 

 peculiar shape and striation of the stones contained in it. Typi- 

 cal boulder-clay may be seen in many places near Ottawa, as 

 in the cutting on the Ottawa, Arn prior and Parry Sound Rail- 

 way near Hintonburg already referred to, at Hog's Back, and in 

 very many places in the area under consideration. In connect- 

 ion with the boulder-clay a word about the distribution ol 

 boulders will be in place. This district is no exception to the 

 general rule that most of the boulders in the boulder-clay and 

 those scattered over a country are from rocks near at hand, and 

 only a few of the harder kinds are carried to a great distance. 

 In this district the boulders commonly seen are limestone, usu- 

 ally flat and angular, and gneiss, granite, etc., more rounded and 

 worn. Dr. Ells has already referred to the great blocks of Black 



