142 Reports & Proceedings — Edinburgh Geological Society. 



segregation of niccolite and nickeliferous pyrrhotite, at the base of 

 a small intrusion of hornblende gabbro near the margin of the 

 Cairnsmore granite. The intrusion is of the nature of a sill, and 

 thus it has affinities with the well-known Sudbury deposit in Canada. 



Lead has been mined in almost every county, but in many cases 

 the mines are now closed down. The chief mines are now at 

 Leadhills and Wanlockhead. The veins of the Leadhills-Wanlock- 

 head district can be divided into two main sets, one running about 

 due north and south and the other about north-west. The north and 

 south set are thought to be the later of the two. About seventy 

 veins in all are known, but only three are now being worked. 

 Leadhills mine (Glengonnar shaft) is about 230 fathoms deep, and 

 works Brow and Brown's veins. Wanlockhead mine (Glencrieff 

 shaft) is about 240 fathoms deep, and works the new Glencrieff vein 

 in its west branch. At Leadhills only galena is worked, but at 

 Wanlockhead both galena and zinc blende are obtained. 



At the present time, in different parts of the new Glencrieff vein, 

 various chemical changes are taking place : thus galena is being 

 dissolved and calcite deposited, in others again calcite is being 

 dissolved and hemimorphite deposited, and in others barytes is going 

 into solution and witherite is crystallizing out. These secondary 

 changes have much influence on the economic character of a vein, 

 making it richer in ore. The Leadhills-Wanlockhead veins are 

 supposed to owe their origin to the intrusion of a dome-shaped mass 

 of granitic rock, which is not exposed, but whose presence is 

 indicated by the numerous dykes of felsite in the area. Over the 

 crest of the dome numerous fissures were formed in the country rock. 

 In the final stages of the cooling of the mass large volumes of ore- 

 bearing hot waters and gases were given off and permeated the 

 whole area. These hot solutions found their way to the larger 

 fissures, and there deposited their burden. Earth movements have 

 disturbed these veins, forming fresh cavities, which have again been 

 filled by secondary deposition of ore. 



2. "The Bituminous Sands of Northern Alberta, Canada." Bv 

 Lieut. S. C. Ells, 2nd C.E.E.B. 



These bituminous sands, of which extensive outcrops occur in 

 Northern Alberta, are of considerable commercial value as material 

 for pavements of various classes. They are of Cretaceous age, and 

 are found in a band overlying unconformably limestones of Devonian 

 age. The sands, which vary much in quality, are always more 

 saturated with bitumen in their lower layers, the amount decreasing 

 upwards : from which fact it is supposed the bitumen has originated 

 from below. A difficulty in the working of these bituminous sands 

 is the considerable (but light in some districts) overburden of the 

 Clear-water shales, also of Cretaceous age. Attempts have been 

 made in the United States to separate the bitumen from the sands, 

 to procure useful commercial products, but at present these have not 

 been very successful. Lieut. Ells illustrated his remarks by a series 

 of excellent slides, giving views of outcrops of the bituminous sands 

 and the methods of working them. 



