IN CAITHNESS. 



221 



and therefore these two latter are the least frequent. 

 Quartz, which is probably the most abundant mi- 

 neral in nature, is met with in all the rock-forma- 

 tions, from granite to the newest alluvial deposites ; 

 and in many regions, in the form of quartz-rock, 

 sandstone, gravel and sand, it occupies districts of 

 immense extent. This quartz-rock passes into 

 gneiss, mica-slate, porphyry and granite ; and sand- 

 stones which, in a general view, are to be considered 

 as members of the quartz series, also occasionally pass 

 into granite. This transition of quartz or sand- 

 stone into highly crystallized rocks of the nature 

 of granite, although very interesting, has not hi- 

 therto been much noticed by geologists. I shall 

 therefore now lay before the Society a short ac- 

 count of an appearance of this description which oc- 

 curs in Sandside Bay, on the north-west corner of 

 Caithness. 



The Bay of Sandside is situated in the parish 

 of Reay, and near the confines of Sutherland. It 

 is open to the north ; but on the south there are se- 

 veral low rugged hills, and on the east and west 

 precipitous sea-cliffs. Three rivulets flow into the 

 bay ; one on the east is named Isald ; the second, 

 in the middle, is Reay-burn ; and the western, the 

 Burn of Sandside. We walked several miles up 

 the burn of Sandside, and found the rocks in every 

 place where we had an opportunity of examining 

 them, to be syenite, granite, hornblende-rock and 



