OF UPPER CANADA AND THE WESTERN PART OF OHIO. 281 



their strike and range to the S. S. W., and that we might in all probability- 

 still meet with the pitted rock which had guided us so well in Upper Canada, 

 on the Detroit River, and perhaps at the head of Lake Erie. Should this 

 prove to be correct, we hoped to unite by actual tracing the rocks of Ohio and 

 Michigan, with those of Upper Canada and New York. We therefore traced 

 the formations south-westwardly, and exploring in our progress the borders of 

 the Detroit River, and afterwards the Maumee, our anticipations were fully 

 realized. 



RocJcs of the Detroit River. — The strata which border the Detroit River, 

 both in Michigan and Canada, we readily identified by their aspect and or- 

 o-anic remains with the beds which immediately overlie the pitted rock on the 

 Maitland. Their exact identity, however, we were fortunate enough fully to 

 establish by discovering the vesicular rock itself well exposed on Gros' Isle, an 

 island at the mouth of the Detroit River, not far from the Michigan shore. 

 The rock at this place consists of a very arenaceous cream-coloured limestone. 

 It is seen in numerous small quarries formerly wrought, and is visible to a 

 depth of about four feet. It abounds in the characteristic lenticular cavities, 

 and contains geodes of sulphate of Strontian identical with those at Goderich. 

 No organic remains seem to occur in it. The beds show an extremely gentle 

 dip to the N. W., and their elevation above the level of the river cannot 

 exceed eight feet. 



The strata on the western side of the river are well seen in a series of 

 quarries about one mile N. N. W. of the village of Truago or Monguagon. 

 They are exposed in shallow excavations for several hundred yards to a depth 

 of from five to eight feet. The prevailing rock is a light gray, somewhat 

 sparry, very fossiliferous limestone. It is occasionally arenaceous and the 

 weathered surfaces assume a yellowish mealy aspect. It is generally of a 

 close texture and very pure. In the partings between the layers we detected 

 the peculiar wavy or suture-like divisions, so abundant in another rock at the 

 Falls of Niagara, and which we had before seen in the limestones above the 

 pitted rock in Canada. 



The rock at Truago strongly reminded us of that seen at Beachville on the 

 Thames, and at the Mills near Goderich. An inconsiderable dip towards the 

 north-west may here be seen. 



Crossing the river here three miles broad, from Truago to Maiden, on the 



