276 THE CANADIAN NATURALIST. [Vol. viii. 



ceaseless attacks of the north-westerly winds. The different 

 methods in which winds affect the configuration of the surface, 

 is discussed at great length in an article in Peterman's Mitthei- 

 lungen by Dr. Frances Czerny of which an abstract appears in 

 'Nature' (Jan. 11, 1877) entitled " The Action of the Winds 

 in determining the form of the Earth." 



IX. — Influence of Snow Drifts as a Geological 

 Agent. 



The description given by Mr. Lieber of angular masses of 

 rock on Mount Bache, slowly moving down hill under the cease- 

 less influence of snow, offers an explanation of the sub-aerial 

 denudation of large areas successively brought under the influence 

 of snow drifts. Natural joints and cleavage in the first instance, 

 greatly facilitate this operation, and those strata which are 

 most subject to joints and weather easily, are the first to suffer 

 from the effects of frost and yield to the influence of pressure. 

 Although some of the strata of the Labrador series are exceed- 

 ingly compact and tough yet others weather very easily, and are 

 rapidly acted upon by frost, thus becoming worn and disinte- 

 grated by the pressure of slowly moving snow-banks on sloping- 

 surfaces. Dr. Hunt briefly describes the rocks of this series as 

 follows : " The anorthosite rocks of the Labrador series present 

 great variation in texture, being sometimes coarsely granitoid, 

 and at other times finely granular. They not infrequently 

 assume the banded structure of gneiss, lines of pyroxene, hyper- 

 sthene, garnet, titanic iron ore or mica, marking the planes of 

 stratification. Probably three-fourths of the anorthosites of this 

 series in Canada, whether examined in place or in the boulders 

 which abound in the St. Lawrence valley, consist of pure or 

 nearly pure felspar rocks, in which the proportion of foreign 

 minerals will not exceed five hundredths.'' * 



Dr. Packardf describes the conical hills of Square Island, as 

 weathering very easily, large masses being detached by frosts and 

 readily crumbling to pieces. The great hypersthenic boulders 

 at Porcupine Hill and on the shores of Lake Melville show a 

 crumbling exterior. 



* On Norite or Labradorite Rock, by T. Sterry Hunt, LL.D., F.R.S. 

 f Observations on tbe Glacial Phenomena of Labrador and Maine, 

 1866. 



