154 Proceedings of Philosophical Societies. [Aug. 



rocks, and therefore not entitled to the name of primitive. 

 According to Professor Jameson, this rock rises from below the 

 mica-slate. Hence it follows, according to Dr. Macculloch, 

 either that the mica-slate is not primitive, or that the primitive 

 are not the oldest rocks. 



Rona consists chiefly of rocks of gneiss and hornblende. The 

 gneiss is traversed by numerous veins of graphic granite. 



The district of Assynt, forming the western part of Suther- 

 land, contains mountains composed of the same granular quartz 

 as occurs in Jura, and therefore, according to Dr. Macculloch, 

 a mechanical deposite. Associated with this rock, occur com- 

 pact gneiss, hornblende slate, and syenitic granite. There occurs 

 also a great deposite of lime-stone, which appears to alternate 

 with the same rock. It is in two very thick beds, with the gra- 

 nular quartz interposed. This lime-stone is dark grey, or nearly 

 black, of an earthy aspect, and minute granular texture, and 

 smells offensive when rubbed. 



On the 21st of May the rest of Dr. Macculloch's paper on 

 the geology of different parts of Scotland was concluded. The 

 granular quartz of Isla, according to Dr. Macculloch, is a me- 

 chanical deposite like that of Jura. It alternates with mica- 

 slate and clay-slate, and with a very important formation of 

 lime-stone. 



Schehallien, according to Dr. Macculloch, consists of a cen- 

 tral ridge of granular quartz, which he considers as a sand-stone, 

 flanked on every side by beds of mica-slate nearly vertical, and 

 containing subordinate beds of lime-stone. 



The vicinity of Crinan is remarkable for containing nearly 

 vertical beds of grey-vvacke and grey-vvacke slate. 



The rocks bounding the valley of Aberfoyle towards Ben Ledi 

 consists of alternations of grey-wacke and grey-wacke slate, with 

 clay-slate : then comes a fine roofing slate, approaching in parts 

 to mica-slate, but consisting of grains cemented by mica-slate. 

 Beyond this, mica-slate makes its appearance. 



A paper by the Rev. William Gregor was also read, contain- 

 ing observations on a species of tremolite found in Cornwall. It 

 occurs in a dark green serpentine rock forming the ridge called 

 Clickertor, in the neighbourhood of Liskeard. It was com- 

 posed of 



Silica 62-2 



Lime 14"1 



Magnesia 12'9 



Oxide of iron 5 # 9 



Water 1-0 



Manganese and soda Trace 



Loss S*9 



100-0 



