96 C. H. GORDON — SYENITE-GNEISS (lEOPARD ROCK) FROM (CANADA. 



Page 



Secondary origin 129 



Similar structures in other rocks 133 



Conclusion 133 



Introduction. 

 general description of the region. 



The apatite region of Ottawa county comprises the area included be- 

 tween the lower portions of the Du Lievre and Gatineau rivers. The 

 chief mining districts occur in Portland and Tenipleton townships, but 

 deposits of greater or less extent are found over nearly the whole of the 

 area. 



The region lies upon the southern flank of the Laurentian axis, and is 

 characterized in large part by a somewhat rugged topograpliy. For some 

 distance nortli of the Ottawa river, the surface is com})aratively level, 

 but this feature gradually gives place to hills which rise to a height of 

 from 500 to 700 feet above the level of the adjacent rivers. The hills are 

 covered with a meager soil, and the forest growth, originally limited, has 

 been largely swe[)t away by fires. The region is drained chiefly by the 

 two rivers mentioned above, which flow southward into the Ottawa river. 

 These streams are of considerable size, have swift currents, and rapids 

 frequently occur. Waterfalls also constitute a [)icturesque feature of 

 these streams. Higli falls, on the Du l.ievrc, has a desc(Mit of about 

 100 feet. 



The country between the streams is dotted with numerous lakes, which 

 drain through small streams with tortuous courses into the Du Lievre or 

 the Gatineau, or soutliward into the Ottawa. These lakes are extremely 

 irregular in slia[)e, with sharply sinuous shorelines, and often contain 

 small islands. 



OEOLOG Y OF THE REGION. 



Character and classification of the rocks. — In order to arrive at a })ro})er 

 understanding of the nature and occurrence of the ellipsoidal syenite- 

 gneiss or leopard rock, it is necessary to introduce a brief description of 

 the geology of the region. The facts U[)on which this descri[)tion is based 

 have been obtained chiefiy from the reports of the Canadian Geological 

 and Natural History Survey.* 



* We are indebted chiefly to the reports of Vennor and Harrington, and to Professor F. D. Adams' 

 account of the typical Laurentian area in the Journal of Geology, vol. i, No. 4, 1893, pp. 325-.340. 

 The map here given was taken from that accompanying H. G. Vennor's report in the Annual Re- 

 port for 1878.. 



