GIIJR — ON CANADIAN CAVERNS. 



175 



on the south shore, which is here ten and a-half miles across. (See 

 sketch, plate ix.). 



The prevailing rocks around Murray Bay belong to the Laurentian 

 formation, their gneissic character being distinctly displayed in a 

 set of beds on the west side of the bay above White Cape, marked 

 by diversities of colour allied to red, green, black, and white ; these 

 beds are described as granitic but very quartzose, with some bands 

 among them possessing the aspect of a slightly micaceous quartz 

 rock. Among the beds is a lai'ge grained red granitic dyke, running 

 in general with their strike, which is north-west, at an angle of from 

 thirty to thirtj^-hve degrees. On the east side of the bay, near Les 

 Ecorchis, the gneiss presents the aspect of a dark grey compact 

 slightly micaceous hornblende slate. It is here also cut by a very 

 coarse-grained dyke, running generally with the stratification, and 

 consisting of quartz and opaque white felspar, while hornblende pre- 

 vails on each side of the dyke towards its contact with the gneiss. 

 Still further to the eastward, before reaching La Heu, there is a very 

 great white dyke of a similar character. No inter stratified bands of 

 crystalline limestone belonging to the Laurentian formation are here 

 met with. The Potsdam sandstone, or white quartz rock, appears 

 above White Point, and at two spots at the east side of the bay. At 

 White Cape the calciferous sand rock is next observed ; it composes 

 the point which bounds the boat cove on the south. The beds here 

 are about twenty-three yards broad with a thickness of fifty-eight 

 feet, and the rock is described as a calcareous sandstone, possessing 

 arenaceous layers iiiterstratified with occasional bands of limestone ; 

 the last forms the uppermost bed as well as a few at the bottom. In 

 some of the arenaceous beds translucent milky quartz-pebbles exist 

 as large as hens' eggs, thus constituting them into conglomerates ; 

 but the grains are generally of such small size as to give an oolitic 

 appearance to the rock : they consist both of limestone and quartz.* 

 Dr. Bigsby found some of the nodules as large as a child's head. To 

 the west of the boat cove are two hummocks of the rock, forming the 

 blufi" from which White Cape takes its name. 



The conglomerate which thus composes the chief part of the preci- 

 pice of White Cape is desciibed by Dr. Bigsby as in strata more than 

 a foot thick, abutting against mica slate in various unconformable 

 positions. — " At the west end the layers are very thin, and are placed 

 vertically, with a south-west direction, in some degree of parallelism 

 to the contiguous mica slate. Near this they are contorted, until 

 gradually toward the centre of the range they become horizontal. 

 Here a singular disposition of the upper laminae is observed. They 

 roof a shallow cave in undulating lines, which descend gently from 

 above, and after curving upwards for a short distance, decline sud- 

 denly on the horizontal strata which constitute the lower half of the 

 sides of the cave."t (See sketch, plate ix.). 



* Geol. Survey of Canada. Eeport for 1819-50. 

 t Ainer. Joui*. of Science, vol. v., p. 212. 1822. 



