358 BELL ON THE VALUE OP 



subsequent eruptive formations, and the material of all sedimentary 

 rocks must have been in a state of igneous fusion. The theory of 

 the. igneous state of the original globe is, however, probably so 

 well established as to require no further proof. It is an axiom 

 without which it is impossible satisfactorily to account for the phe- 

 nomena of volcanoes and hot springs, the elevation of mountains, 

 the increase of temperature on penetrating into the earth, the phe- 

 nomena of terrestrial magnetism, the formation of crystalline 

 rocks, and the flattening of the earth at the poles. In the third 

 and concluding part of this paper I shall advert more fully to this 

 hypothesis, of the conditions which must have co-existed with the 

 earth's original fluid state. 



Art. XXV. — Roofing Slate as a Source of Wealth to Canada. 

 A visit to the Walton Slate Quarry ; by Robert Bell, 

 C. E., of the Geological Survey of Canada, and interim 

 Professor of Natural Sciences in Queen's College, Kingston. 

 The rarer treasures of the mineral world are not always those 

 which yield the largest returns for the working. According to 

 Darwin, it is remarked in South America, that " a person with a 

 copper mine will gain ; with silver, he may gain ; but with gold he 

 is sure to loose." Continuing this sort of comparison to the coarser 

 mineral products, it could not be difficult to show that there are 

 many of them which pay better, even than copper mines. In the 

 midst of the excitement about copper and gold in the Eastern Town- 

 ships, our valuable treasures in roofing slate have not been altogether 

 overlooked. But before proceeding to point out the importance 

 of this source of wealth, let us consider for a moment the value of 

 slate quarries in other parts of the world, and ascertain how 

 others turn their advantages, in this respect, to profitable account. 

 The slate quarries of Wales are perhaps the most extensively 

 wrought in the world. The Penrhyn Quarry, six mdes from 

 Bangor in North Wales, and owned by the Hon. Colonel 

 Pennant, has been worked to a depth of nearly 900 feet by 

 successive benches or chambers, each sixty feet below the next 

 above. The lowest of these have been reached by sinking shafts 

 and runningjhorizontal adits or drifts, from which the material has to 

 be raised perpendicularly. The cost of working is thus much 

 increased, but notwithstanding this circumstance, the quarry is 

 believed to pay nearly a hundred per cent, profit, and the annual 



