276 OBSERVATIONS ON THE GEOLOGY OF THE WESTERN PENINSULA 



about thirty miles west of Hamilton, the drift contains a gradually lessening pro- 

 portion of the materials of the red shale and sandstone, while to the west and 

 northwest of Brandtsford it ceases altogether. 



In the vicinity of Paris, however, about thirty-eight miles west of Hamilton, 

 rolled fragments of the upper group of limestones begin to make their appearance 

 in the streams and on the surface; and, growing more frequent as we proceed west- 

 ward, prove, near London, the predominant material of the drift. It need scarce- 

 ly be remarked, that the N. N. W. trend of the terrace formed by the Niagara 

 limestone would, in connexion with the admitted southerly course of the drift, 

 give rise to the distribution of the materials here described. 



Range of the Gypseous Shales. — Crossing the Niagara river in the neigh- 

 bourhood of the Tonewanta, this group of strata stretches in a narrow belt some 

 distance south of the terrace, and parallel with it. It intersects the Welland 

 canal, and follows the course of Grand river to the vicinity of Paris. From this 

 point these shales sweep towards the north to conform with the flexure of the 

 mountain ridge, and passing a little east of Guelph range towards the southern 

 end of Lake Iroquois. The gypseous shales are well exposed, in excavations 

 for plaster, in two places on the Grand river. One of these is near the Wel- 

 land canal and the other at Paris, where the top of the formation rises per- 

 haps forty feet above the level of the stream. The shales here contain the 

 curious hopper-shaped cavities familiarly known as a distinctive feature of the 

 upper part of the formation in New York. They are accompanied, likewise, 

 by the remarkable vesicular or pitted limestone, which, throughout the west- 

 ern counties of that state furnishes so good a guide to the gypseous beds. 



Range of the Vesicular Limestone. — This is ordinarily an impure, bufF- 

 coloured, subcrystalline limestone, abounding in small lenticular cavities, ha vino- 

 very much the shape of tabular crystals of selenite, to which they probably 

 owe their origin. Remarkable for the permanency of its peculiar features and 

 for its wide diffusion, this stratum has proved of the utmost service in our re- 

 searches, as a safe and convenient base in establishing the super-position of 

 the other more variable formations. Tracing the less easily identified strata 

 by it, it served us as a grand lithological horizon from the Niagara river 

 through Upper Canada into Michigan and Ohio. 



