624 THE LOWER SILURIAN PERIOD. 



in lime. These slate districts, however, often contain beds of quartz 

 rock which form rocky ridges, from which boulders have been 

 scattered abroad, and which, by damming up the surface waters, 

 produce lakes and bogs, — an effect also often produced by the ridged 

 structure of the slate itself, and the impervious subsoil which it 

 affords. Wherever, as for instance in Northern Queen's and Lunen- 

 burgh, the slate is sufficiently elevated for drainage, and not encum- 

 bered with surface stones, it supports fine forests and valuable 

 farms. Where quartz rock prevails, the soil is almost invariably 

 extremely stony and barren. Instances of this occur in Southern 

 Queen's, near Halifax, and in the hills near the St Mary's River. 

 The mica slate is little better, for though it does not furnish fragments 

 to cumber the surface, it scarcely affords any soil. 



The granite and gneiss in some places appear in precipitous hills 

 of considerable elevation, and in others form low and uneven tracts. 

 Their decomposed surface affords a sandy quartzose soil, often strewn 

 with large rounded blocks of granite, which in some instances cover 

 the whole surface, so that a granitic hill appears to be merely a huge 

 mound of boulders. This appearance results in most cases from the 

 nodular character of the granite, or from its consisting of great balls 

 of hard resisting rock, united by a material of more perishable 

 character. Where the granite or gneiss is wholly of a resisting 

 character, its surface is sometimes almost entirely bare, or coated 

 only with a layer of peaty vegetable soil. This occurs to a great 

 extent in the peninsula of Cape Canseau. The granitic soils in their 

 natural state often support fine groves of oak and other deciduous 

 trees ; but the bare summits, destitute of soil, are clothed only with 

 stunted spruces and various shrubs and mosses. Where the original 

 vegetation has been destroyed by fire, the granite hills often become 

 perfect gardens of flowering and fruit-bearing shrubs. I have col- 

 lected in a day in August, on a single granitic eminence, sixteen 

 species of edible wild fruits. The alkaline matter afforded by the 

 waste of the granite is especially favourable to the growth of these 

 plants as well as of ferns ; fields of which (chiefly the common brake, 

 Pteris aquilina) may be seen in the valleys among the granitic hills 

 to attain the height of four feet. 



Useful Minerals of the Lower Silurian of Nova Scotia. 



Gold. — At the date of the publication of " Acadian Geology " in 

 1855, no actual discovery of gold in Nova Scotia was known to have 

 been made. At that time I could only indicate the possibility that 

 such discoveries might be made, and the most probable localities; 



