No. 3.] SPENCER — PALEOZOIC GEOLOGY. 133 



Mr. Beasley and myself connected the thickness between the adja- 

 cent summit of the Medina group, which is 264 feet above the 

 lake, by levelling (and allowing for dip) with the mouth of the 

 well of which we had the record, and were thus enabled to calcu- 

 late accurately the thickness of the formation. 



Before advancing further we will give u tabular view of the 

 four sections measured. 



The first section is at the western end of Dundas, (nenr the 

 place where the Artesian well was sunk.) The height of the 

 mouth of the well was found to be 139 feet above Desjardin's 

 Canal. Afterwards we levelled to the summit of the cliffs along 

 the south-western side of the ravine, which is formed by the 

 union of the two streams from Spencer's and Webster's Falls — 

 the highest point of the exposed rocks being at the junction of 

 the two glens, where the top beds are composed of the cherty 

 bands of the same horizon as those which form the capping strata 

 south of Hamilton. By means of this section and the Artesian 

 well, we were able to ascertain the whole thickness of the Medina 

 formation, the whole thickness of the Clinton formation, and 

 the lower portion of the Niagara proper. 



But the western side of the ravine is more than one hundred 

 feet lower than the eastern side, although the rocks are nearly 

 horizontal. This has been owin"- to the local denudation in the 

 spur of rocks between two great valleys, which will be noticed in 

 a future paper on the surface sjeology. 



The ravine or canon just referred to is more than 300 feet deep, 

 if we calculate from its eastern (or rather north-eastern) side. 

 Owing to the absence of the higher beds of the series, we levelled 

 up the escarpment on the opposite side of the great glen, at the 

 Limekilns, just east of the " Peak," where the highest rocks are 

 516 feet above the lake, although the soil rises a few feet higher 

 a short distance to the northward. 



By these measurements, and the necessary calculations in cor- 

 relating the adjacent measurements, it was found that the whole 

 thickness of the Niagara group is 800 feet at Dundas, of which 

 the lowest 545 feet belong to the Medina series. 



The second section is along the Sydenham road at Dundas. 

 The third section is at Hamilton, between the head of James 

 street and the Jolly Cut road. The fourth section, as we have 

 seen, was taken aloniz; the Rosseaux Creek to Albion Falls. 



