588 Mineralogy and Geology of Nova Scotia, 



slate from uncultivated ground, or clay from the common, to be 

 exposed to the air for a year under a shed which protected it 

 from the rain, and frequently turned, it would, upon lixivi- 

 ation, yield copperas; but clay from the side of a cellar wall, 

 or alum slate from the streets of Halifax, in the same situation, 

 would form alum, because it would have imbibed a portion of 

 alkali from the wash of the yards. As these clays differ in 

 quality, being formed from different varieties of slate, it is cus- 

 tomary, previously to establishing alum works, to ascertain by 

 experiments the kind, and the exact quantity, of alkali that 

 will make the clay most productive. Some clays are mixed 

 with peat, dried and burnt ; others are placed under sheds, 

 and frequently turned, sprinkling them with urine till the 

 proper quantity has been added. Both wood ashes and 

 urine are found necessary for some. It is also necessary to pay 

 attention to the season in which the clay is lixiviated ; for 

 alum forms most readily in the hottest season, while other 

 salts are formed from the same materials in the cooler part of 

 the summer. 



Some of the clay near Halifax that I have tried has become 

 so highly impregnated with alum as to present a glittering 

 appearance by candle-light or in the sun, the surface being 

 half-covered with crystals of alum. As our barren soils 

 contain the materials in abundance, it is probable, that, at a 

 future period, there will be extensive alum works in this 

 province. 



Besides the slates, there are other matrices of alum in the 

 province. I have observed alum formed from the soil of some 

 of the meadows on the Souiac, which contain salt springs, and 

 lie contiguous to gypsum. It is formed, also, in the decayed 

 portions of the fine-grained, hard, grey rock which alternates 

 with the sandstone at the Joggins, near the Cumberland coal 

 mines. The band of slate upon which the town of Halifax is 

 built, after running westward five or six miles, meets a mass of 

 granite, where it ends. Eastward, it may be traced as far as 

 Petpiswich, varying from one to two miles in breadth. Upon 

 the north side of this band there is a breadth of about 100 

 yards of pale siliceous slate, part of which is harder and 

 heavier than whinstone. South of the Halifax slate, the band 

 of whinstone extends in breadth southward five or six miles; 

 part of a band of slate appearing again near the pent on the 

 west side of the entrance of Cole Harbour. Northward, the 

 band of whin extends from the three-mile house at the basin, 

 where it commences, to the sixteenth mile on the Windsor 

 Road, where a considerable band of slate occurs. Where 

 these bands of slate join the granite on the west, they become 



