268 Dr. Bigsby's Sketch of the Topography 



phurous odours. On visiting the seat of the disturbance, he 

 found the appearances I have described. 



The north shore of the St. Lawrence, three miles and a half 

 above Brockville, and a small group of islands, seven miles 

 above that town, are principally of fine granular gneiss; but 

 in both places it becomes porphyritic, and i-ed. It is there 

 traversed by granitic veins, whose white quartz, red felspar, and 

 copper-coloured mica, are in crystalline masses, varying from 

 one to three inches in diameter. Quartz veins are frequent 

 everywhere. 



Iron pyrites, in very large quantity, is common throughout 

 the distance from Kingston to Brockville. Magnetic iron ore 

 occurs high up the Gananoque River, and on an islet in the 

 St. Lawrence, one mile south-west from the mouth of the Ga- 

 nanoque. Plumbago occurs in a creek six miles N.E. of 

 Kingston. The late Mr. Spilsbury, surgeon R.N., showed me 

 some good specimens. It is found also on Gananoque Lake 

 (Gourlay). The only other mineral belonging to this district, 

 with which I am acquainted, is schorl. This is plentiful every- 

 where : there are perhaps few islands in the outlet without it ; 

 it is imbedded also in the crystalline quartz rock. 



A considerable mass in confused crystallization exists three 

 miles and a half below Kingston on the water side ; but the 

 most remarkable locality is Yeo's Island*. This island is 

 small, naked, and high, divided into two parts ; on the summit 

 ofthe south-western of which is the bed of schorl, twelve feet in 

 diameter. It does not consist of schorl only, but is a confused 

 aggregate of white translucent quartz, of opaque cream-coloured 

 felspar, of greenish yellow mica, and the schorl is intermixed 

 in shapeless masses of from one to three feet in diameter. The 

 quartz and felspar are in their usual forms. The mica is brass 

 yellow, but with a delicate tinge of green in certain lights. It 

 is in flakes an inch square, grouped confusedly, and so tough, 

 that, although it is in masses of a yard in diameter, small frag- 

 ments are procured with difficulty with a large hammer. The 

 schorl occurs as a very close accretion of large crystals, with 

 broken terminations, cemented by a film of mica, and dipping 

 into the rock southerly, at an angle of 70°. They have no de- 

 terminate number of sides; but resemble ajascis, composed of 

 unequal rods. From this the principal deposit, several ramifi- 

 cations of like materials pass off to the sides of the island, want- 

 ing only the mica. Veins of felspar and quartz, very largely 

 crystallized, are met with in other parts of the island, contain- 

 ing schorl in six-sided prisms from 1 to 8 inches in length. 



* Opposite M'Guggin's tavern, and outside ofthe head of Tar Island. 



Of 



