J. G. Goodchild—On Drift. 499 



A large proportion of the stones are either more or less blunted 

 and striated, or else show obscure traces of striee, which evidently 

 were at one time much more distinct. 



Angular and unscratched stones occur throughout the till, fre- 

 quently outnumbering those that are glaciated ; and well-scratched, 

 and quite unworn stones are by no means absent from the sand and 

 gravel group. 



The proportion of material water-worn and sorted according to 

 size, and of blocks which are arranged with their longer axes 

 parallel to the horizon, steadily diminishes as we approach the heads 

 of the river-basins. 



Much of the drift lies in elliptical mounds, which frequently 

 spring from a rocky projection ; and their longer axes, in most cases, 

 conform in direction to that of the general line of waterflow of the 

 place where they occur. 



Not often, save at the heads of valleys, does the drift fill hollows : 

 in the plains it is usually moulded over bosses and ridges of solid 

 rock ; and the slopes of the mound in this case conform to the sub- 

 jacent bedding planes of the drift. 



Pipes of fine sand and gravel sometimes extend several feet up- 

 wards through the till; and inclined and rudely lenticular masses of 

 finely laminated clay occur equally in the sand and gravel group, 

 and in the upper and lower tills. 



The limited horizontal extent of each mass of this gutta-percha 

 clay is shown to be original by the coiiformity between the outer 

 lamination and the bounding surfaces of each mass. 



Lastly, undisturbed stratification may usually be found extending 

 a long distance horizontally through each section : where crushed 

 and contorted beds occur, they are either intercalated between un- 

 disturbed strata, or, if they occupy the surface, the beds beneath show 

 no derangement. 



As the marine theory of the origin of till leaves so many facts 

 unexplained, that it is being rejected by most glacialists, it will be 

 passed by here without further mention. 



The theory which seems to find most general acceptance with 

 geologists is that which assumes that the till originated through the 

 long-continued scraping and rasping of the rock surface by the gritty 

 sole of the ice-sheet, studded with boulders that had been wrenched 

 from its rocky bed, the resulting detritus being shoved along between 

 the moving ice and the rock to the sheltered spots where it finally 

 acciimulated as till. 



It is obvious that a deposit formed in this way must necessarily 

 be quite unfossiliferous, because the enormous force exerted upon 

 the mass by the advancing ice-sheet must have been sufficient to 

 grind any organisms which chanced to find their way there into the 

 finest mud. 



For the same reason such a deposit must be quite devoid of stratifica- 

 tion. The ice which exerted so powerful an abrading influence upon 

 every part of the most irregular and hardest rock surface, glaciating 

 boss and cavity alike, could not fail to knead up any unconsolidated 



