L. A. Necker de Saussure Voi/age en Ecosse. 197 



own beds. The inclination of the beds is generally like that of 

 the surrounding districts to the south-east. South of the foot 

 of these hills commences the formation of red sandstone ; north- 

 ward are the beds of the greywacke formation. The great 

 chain which extends from the mull of Galloway, across Scot- 

 land, to St. Abb's-head is greywacke, properly so called, and 

 greywacke slate. The fragments sometimes attain the size of a 

 hen's egg. The subordinate beds common in this formation, 

 such as the clay, alum, and siliceous slates, as well as a black- 

 coloured limestone are found frequently in these mountains. 

 The greywacke acquires in this country great importance by 

 the number, extent, and richness of the metallic veins, which 

 abound in this formation. The lead hills' district at 2,300 feet 

 of elevation, towards the centre and on the northern face of the 

 chain, exhibits the most considerable mining operations of 

 Scotland ; lead, copper, iron, and manganese occur in abun- 

 dance. 



The red sandstone forms in Scotland the inferior beds, 

 whilst the coal-sandstone is superincumbent on it ; the former 

 of which exhibit great disorder in their direction, as well as in 

 their inclination. Yet on the whole, they form a concave stra- 

 tification, rising up on all sides upon the edges of the containing 

 basins. 



With regard to local and independent formations, it appears 

 certain, that Scotland is hitherto the only country where such 

 districts have exhibited in a clear and evident manner, those 

 important geological characters, which distinguish them from 

 the ordinary class of formations, although these mineral masses 

 have their counterparts in other countries. The characters of 

 the rocks of this class are: 1st, They are never stratified, but 

 occur under ihe form of amorphous masses, prisms, balls, and 

 tables of little length. 2d, They are never interposed between 

 two beds of foreign rocks, so as to form between these, a bed 

 of indefinite length, constantly parallel to the strata. 3 cZ, They 

 never conform to the stratification, whether general or parti- 

 cular, of the formations and rocks which surround them. 

 4th, They penetrate into the middle of the surrounding rocks, 

 filling up their rents, in the form of veins, which veins some- 

 times evidently proceed from a mass similar to themselves ; 

 sometimes they appear insulated, although never at a very 

 great distance from a similar mass. Hence it is obviously very 

 difficult, with respect to the independent formations, to seize 

 exactly their relations of antiquity, not only with the formations 

 which adjoin them, but also with other independent formations. 

 They may be divided into three orders; ls<, Those in which 

 granite forms the predominating rock ; 2d, Those characterized 

 by the abundance of porphyry; and 3d, Those which consist in 

 a great measure of greenstone-trap and basalt. These divisions, 



