H. S. POOLE ON THE GOLD-LEADS OF NOVA SCOTIA. 311 



slate give the leads a ribbon-like structure, and suggest a series of 

 expansions of the fissures and successive depositions of quartz marked 

 by the adhering films of slate. 



As it is from mining experience that the weightiest arguments 

 against the bedded origin of the leads can be adduced, fuller refer- 

 ence is made to matters that aftect the mining than may seem war- 

 ranted in a geological paper. There are yet a few observations 

 worthy of note. The constituents of the leads are not uniformly 

 mixed : in the Hay lead 60 ounces of gold were aggregated in one 

 spot ; and extended workings in the same lead failed to find else- 

 where more than a few pennyweights of gold to the ton of quartz 

 and calcite, the latter a principal component of the lead. The 

 working portions of the leads are small, and the yield of gold not 

 uniform. So far, experience does not encourage extended search 

 beyond the limits of a working " streak " by sinking or driving levels ; 

 and the writer is not aware of the discovery in depth of a paying 

 streak not known on the surface. 



Relative Age of the Leads and Granite* 



It has been suggested that the so-called granites which blot large 

 portions of the Palaeozoic belt are not intrusive, but are merely highly 

 metamorphic rocks. That in every case they are so seems hardly 

 compatible with structural characters observable, and which may 

 here be briefly noticed. On traversing the country under review, 

 the hill-toj)s are often seen denuded of all detrital matter save a few 

 isolated boulders, and the junction of the granite with the sedimen- 

 tary rocks is in many places exposed. 



At Mooseland, for instance, exposures show the line of contact as 

 clearly as would wooden models specially designed to do so ; and 

 there the following observations may be made : — Granite occupies 

 tlie highest ground, presenting a curved margin, in part parallel 

 and in part transverse to the strike of the bedded rocks, which are 

 highly inclined and locally broken. Tongues and veins extend 

 from the parent mass of granite between the opened strata ; and in 

 one about 2 feet wide there lies obliquely a thin slab of quartzite 

 half an inch thick and 6 feet long, which has evidently fallen awav 

 from one of the walls. Another spot shows a larger slab, about 10 feet 

 long and 1 foot thick, which has fallen forward into the body of the 

 granite while the latter was still in a plastic state. Its original site can 

 without doubt be ascertained by measurement. Parallel to a vein of 

 pure quartz a vein of granite only half an inch wide, 200 feet from 

 the main mass, demonstrates the plasticity, if not fluidity, of the 

 granite ; but whether it was derived from excessive local metamorphism 

 or injected from below, is open to question. The sharpness of the 

 broken edges and the locally disturbed condition of the beds along 

 the line of contact certainly suggest the latter, while the crystal- 

 line structure of the protruding tongues seems to confirm it ; for, as 

 in a chilled casting, the crystals are coarse in the centre and fine 

 next the walls, from more rapid cooling. The crystallization of the 

 mass is, in spots, streaked and irregular near the sedimentary rocks ; 



