130 The Geology of the Cluden Basin. 



From the mouth of the gorge at the manse, straight up 

 stream to Ayrshire and I.anarkshire on the north, and from Mull 

 of Galloway and Sohvay Firth to St Abb's Head in Berwickshire 

 the prevailing rock is greywacke, commonly known as whinstone. 

 Greywacke is a German word, coined by the miners of that 

 country, and adopted by the scientists here. Fortunately in this 

 case only the name has been dumped on our moors, and not the 

 stone itself. It is a ^■ery hard, durable rock of great antiquity, 

 and is associated with bands of shales. These shales, grey, 

 black, and green, are much softer, and sometimes charged with 

 fossils, which prove them to ha\'e been deposited in the Silurian 

 epoch. This formation (Silurian) is the second oldest sedimentary 

 rock containing the remains of animal life in the whole world, 

 and perhaps the oldest in Scotland. In texture and bedding 

 the stone varies greatly. In a roadside quarry at the foot of the 

 Long Wood we ha^■e fine silky shales or mudstones, capable 

 almost of being made into honing stones. At Morrington Quarry 

 and Routen Bridge we find the ideal whinstones or sandy mud- 

 stones. They are medium grained, and were deposited in thick 

 beds, thus enabling them after a prolonged period of weathering 

 to resemble massive blocks of masonry. South of Shawhead the 

 deposit is thin bedded, and consequently it weathers into shattery 

 fragments. Near Dunscore the rock is much coarser, resembling 

 a very fine gravel, and known as the Queensberry grits. At 

 Craigenputtock and Bogrie there are several bands of a coarse 

 conglomerate, containing large pebbles of quartz and schist. 



In Britain the Silurian epoch represents a deposit of about 

 22,000 feet of rock, and in relation to this district it is di\ided 

 into seven different ages. These various ages are again divided 

 into zones and sub-zones, each of which is characterised by an 

 altered condition of deposit and by a distinct type of fossil life, 

 the graptolites. The Silurian sea stretched from the Highland 

 barrier in Dumbartonshire and Stirlingshire over the whole South 

 of Scotland to Cumberland and Westmoreland. At Routen 

 Bridge there is a fine display of medium-grained greywackes. 

 These massive thick-bedded rocks are classed as belonging to 

 the Queen.sberry grit series, and were deposited during the 

 Tarannon age. The group of deposits immediately underlying 

 these grits and greywackes of the Tarannon period belongs to 

 the Llandoverv age, and is represented in this region by the 



