Mineralogy and Geology of Nova Scotia. 585 



make an excellent material for roads, as the copperas they 

 form is slowly changing a portion of the soft soil to stone. 



The vitriolic slate which lies under peat earth is never en- 

 crusted with oxide of iron, or petrified earth ; on the contrary, 

 the stones frequently have a worm-eaten appearance, the spaces 

 near the surface, which were once occupied by pyrites, being 

 empty. 



Whinstone, in the same situation, appears to be in a state 

 of slow decomposition, the surface resembling a soft white 

 sandstone. The same effect is produced upon these stones 

 by remaining for a considerable time under heaps of stable 

 manure, and also, in some degree, by the covering of the turf 

 of old woods. This proves the absurdity of the practice, still 

 too frequent near Halifax, of repairing roads occasionally with 

 soil from the ditches; as a material is introduced in the rich 

 mould formed from the manure washed from the road, which 

 not only serves to make dust in summer, and mud in the spring 

 and autumn, but also to dissolve a portion of the stony part 

 of the road. 



It appears, therefore, that peat earth must be useful to the 

 agriculturist upon vitriolic soils, which are too gravelly, as it 

 will change a part of the stone to earth, although it will not, 

 like carbonates of lime, change it to a fertile soil. The beds 

 of bog ore found under peat swamps have probably originated 

 in the vitriol of the slate. Small beds of this ore, in a 

 quantity too inconsiderable to be worth working, may now be 

 found near Halifax ; but, as it appears to be necessary to its 

 rapid formation that the ground should be exposed to the sun, 

 I conceive that it will be more abundant hereafter. 



Where a barren slaty soil is covered by a growth of firs 

 two or three hundred years old, the surface is usually over- 

 spread with a layer of turf from 6 in. to 1 2 in. in thickness. 

 Beneath this turf, which excludes the external air, the slate 

 appears more free from rust, more solid, and holding more 

 bright pyrites near its surface, than that which has been for a 

 considerable time exposed to the air. Yet there is always at 

 the bottom of the turf a considerable quantity of charcoal, 

 which, together with an abundance of raspberry seeds, proves 

 that the ground was open previously to the growth of the firs. 

 It seems, therefore, that the pyrites is reproduced after the 

 turf becomes so thick as to exclude the external air in a con- 

 siderable degree. 



The oxygen of the oxide of iron and sulphate of potash 

 probably unites with the charcoal, while the iron and sulphur 

 again form pyrites in the cavities where it formerly existed. 

 It would follow from this supposition, that, while a country is 



