No. 3.] SPENCER — PALAEOZOIC GEOLOGY. 139 



3.7 " 



Thin shaly sandstones [ 



I — 6.7 " 



By this menus it will be seen that the whole series does not 

 materially alter in thickness, but that the undulations of the 

 surface of the -'Gray Band" resulted from unequal deposits of 

 sand along- the sea mnrgins, and afterwards the inequalities were 

 filled up by sediments of sliirhtly different character. Sometimss 

 the ''Gray B.ind " shows ripple marks on its upper surface, 

 while the more shaly partings have their surface characterised 

 by wave action. 



At Grimbsy, the lower portion of this band is of the usual 

 gray color, but it passes into bright red sandstones irregularly 

 deposited, and conspicuously mottled by large spots of a gray 

 tint. At this] locality the Artliropliycus harlani is very abun- 

 dant, and though found in both the gray :ind red sandstones, 

 it is more common in the former. 



At Duiidas the capping portion of the '' Gray Band " consists of 

 a bluish sandstone resembling quartzite, though this subdivision 

 in the character of the beds is not noticeable at Hamilton. 



All the thicker beds of Medina sandstone form excellent build- 

 ing material, though difficult to work on account of its compact- 

 ness and toughness. 



Along the canon of the Niagara River more than 200 feet 

 of the shales are exposed. So, also, there are excellent exposures 

 in many of the gorges about the head of Lake Ontario. Perhaps 

 the best section of the shales is to be obtained by following up 

 the stream which flows into Burlington Bay after passing by the 

 village of Waterdown. In the deep gorge of this stream the 

 upper 250 feet of Medina shale is more or less exposed, though 

 in some places covered by land-slides. The base of the Medina 

 is exposed at a short distance east of Oakville. 



At Dundas, an Artesian well was sunk a few years ago, and 

 the following is the log of the boring, as published in the Dundas 

 Banner : 



