272 American Association . 



axis, and proceediug in a bearing S. S. W., for seven miles, it 

 attains the southern boundary of the township, close upon the east 

 side of the northern prolongation of the intrusive syenite. It runs 

 in the same bearing for about 3 miles along the eastern side of 

 this into Chatham, and becomes deflected to the S. E. by the 

 main body of the syenite, to which it runs parallel for about three 

 miles. It then folds upon the axis of a synclinal, and running N. 

 N. E. for upwards of five miles, returns into Wentworth, where it 

 gradually bends round more to the eastward, and in about five 

 miles reaches a position in the Gore of Chatham. It here folds 

 over upon the axis of an anticlinal, and turning S. S. E. it main- 

 tains this course for about eight miles, in wdiich it crosses into the 

 Seigniory of Argenteuil and reaches the vicinity of Lachute, 

 where it once more bends upon a synclinal axis, and proceeding- 

 eastward for about a mile, plunges under the Potsdam Sandstone 

 and is lost. 



In the wanding course derived from the plications of the 

 strata, the limestone usually presents a valley on the geogra- 

 phical surface ; but to the "west of all the folds that have been 

 described, a bold ridge of gneiss runs from the front of Grenville 

 to the rear of Harrington, the distance being about 20 miles and 

 the bearing N. N. E. On the west side of this ridge, about mid- 

 way of the length, there are two areas about five miles long and 

 broad, presenting the forms of valleys, -which are underlaid by 

 limestone, so distributed as to render it probable that they are two 

 outlying parallel troughs joined together, belonging to the same 

 calcareous sheet as the one described. There would thus be four 

 main synclinals and three main anticlinals, and the breadth they 

 occupy altogether is about eighteeen miles, giving about four and 

 a-half miles for the breadth of each undulation. 



Bands of dolomite sometimes accompany the limestone, 

 which is often interstratified with bands of quartzite. The 

 quartzite appears to be heaviest near the junction of the 

 limestone and gneiss, becoming thinner and less frequent as 

 we recede from the calcareous rock. The greatest mass of 

 quartzite met with, had a vertical measure of 400 feet, and it was 

 in stratigraphical position beneath the limestone. The quartzite 

 and the gneiss on each side of the limestone are often very thickly 

 studded with garnets, and in some cases the aggregation of these 

 is so close as to constitute a granular garnet rock. In the Gore of 

 Chatham a band of limestone about three-fourths of a mile to the 



