THE LAtJRENTlAN ROCKS OF CANADA. 3 



valley continues northward into Harrington, and after a short inter- 

 val shows an isolated patch of limestone of about a mile and a half in 

 length, by a mile in breadth, possessing, of course, a synclinal form. 

 Beyond this, the valley splits into two, and while one branch runs 

 rather north of N. E>, the other turns IS", of E. Each of these val- 

 leys is paved with limestone, the distribution of which shews a con- 

 tinuation of the synclinal form, with a bend more to the eastward 

 than before. 



The calcareous band on the western side has been traced to the 

 north boundary of the township of Harrington, whence it crosses into 

 Montcalm. It there appears to turn to the westward, but it has not 

 yet been farther accurately examined. The eastern branch has been 

 followed for between six and seveu miles into Wentworth, when it 

 appears to turn upon an anticlinal axis, and proceeding in a bearing 

 S. S. W., for seven miles, it attains the southern boundary of the town- 

 ship, close upon the east side of the northern prolongation of the in- 

 trusive syenite. It runs in the same bearing for about three miles 

 along this eastern side, 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, 

 tvhere 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 maintains 

 this course for about eight miles, in which 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 winding course derived from the plications of the strata, the 

 limestone usually presents a valley on the geographical surface ; but 

 to the west of all the folds that have been described, a bold ridge of 

 gneiss runs from the front of Grrenville to the rear of Harrington, the 

 distance being about twenty miles and the bearing N. N". E. About 

 midway, on the west side of this ridge, there are two areas about 

 five miles long and broad, presenting the form of valleys, which 

 are underlaid by limestone, so distributed as to render it pro- 

 bable 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 eighteen miles, giving 

 about four and a-half miles for the breadth of each undulation. 



