120 Canadian Record of Science. 



factors concerned in their deposition. Whether, under 

 these conditions of a more rapid rate of supply of 

 detritus than rate of depression, it happened that a 

 series of land deposits, the shoreward extension of the 

 sandstones, was formed, is at present doubtful. It seems, 

 however, that when there were such broad sandy tidal 

 flats as existed during the Medina, dry at least at low water, 

 as shown by the mud cracks, that the lighter siliceous sands 

 may have been blown up on the beach in the form of sand 

 dunes, leaving the heavier ferruginous sands as a residuum. 

 Such a suggestion may possibly account for the single band 

 of grey sandstone, usually called the grey band which ex- 

 tends across Ontario from Niagara Falls to near Colling- 

 wood. This band caps the Medina deposits, and is a fine 

 textured compact sandstone, with an average thickness of 

 about twelve feet. It is traceable from east of the Niagara 

 gorge to Hamilton, and thence northward it is seen at in- 

 tervals from Flamborough West to Nottawasaga, varying 

 in thickness from ten to twelve feet, but preserving a nearly 

 uniform lithological character. On lot 24, concession 10, 

 of Nottawasaga, the maximum thicknesss of thirty-five 

 feet is reached. West of the townships of Nottawasaga 

 and Collingwood the grey band is wanting and the Clinton 

 is found in several places to rest directly upon the red and 

 green shales of the Medina. Where the surface of the 

 band is uncovered (and it may be seen in many places, as 

 the softer overlying Clinton has been eroded away) it 

 presents a peculiar undulating surface quite comparable to 

 that found at the present day in localities from which a 

 sand dune has recently migrated. In one locality at least, 

 in a cutting transverse to the grey band, by which a road- 

 way ascends the Niagara escarpment, near Grimsby, the 

 band shows excellent cross bedding on a very much larger 

 scale than is usually seen in typical water laid deposits of 

 similar texture. (See figure 3.) The occurrence of this 

 large scale cross bedding, the undulatory character of its 

 surface, the irregularity of its thickening, and the fact that 



