196 Aiialyiia of Scientijic Books, 



cated as the southern limit of the mica-schist formation to the 

 base of the Grampian mountains. This breadth is not equal 

 over all the extent of the stripe, for whilst at the west it occu- 

 pies the whole length of the peninsula of Cantyre, on the east 

 coast, it is scarcely a few hundred fathoms broad. 



The greyvuacke formation is the only one of transition which is 

 found in Scotland, but it occupies so large a space, and exhibits 

 such remarkable phenomena, as to merit the mature considera- 

 tion of geologists. The limit where the greywacke formation 

 commences is a line drawn from N.E. to S.W., along the foot 

 of the Grampians, from Stonehaven to Renton, a village situ- 

 ated between Dumbarton and Loch-Lomond, and this for- 

 mation stretches considerably into England, where it con- 

 stitutes a part of the mountains of Cumberland and West- 

 moreland. In the midst of this mass of greywacke we have 

 a discontinuity in the basins of the Forth and Clyde, which is 

 filled up by the secondary rocks, of red sandstone and coal 

 sandstone, which again are traversed, and often covered by 

 basaltic or trap masses. These same secondary beds do not, 

 however, fill up completely the bottom of the basin, but we 

 observe issuing from the midst of the sandstone, and rising to 

 heights more or less considerable, stratiform masses, composed 

 of rocks subordinate to the greywacke formation, which consti- 

 tute chains of hills, hillocks, or insulated rocks of no small 

 magnitude. The puddingstones are the oldest, and conse- 

 quently the lowest part of the greywacke formation, and they 

 constitute the northern borders of the basin of red sandstone. 

 Secondly, we have the greywackes, properly so called, which 

 form the southern borders of the basin, namely, the long chain 

 of the Lammermuirs, and which form in Scotland at least the 

 newest beds of the formation which bears their name. Lastly, 

 we have beds subordinate to the puddingstones, or intermediate 

 between these and the greywacke, beds which form protuber- 

 ances that rise suddenly from the bottom of the basin when the 

 red sandstone is deposited. The composition of the pudding- 

 stone is like that of the greywacke, fragments of primitive rocks, 

 under the form of pebbles or rounded blocks, united by a ce- 

 ment of granular micaceous quartz, sometimes of the nature of 

 clay-slate, sometimes by a reddish ochry clay, and rarely by a 

 calcareous cement. 



Beds often pretty thick, but not divided into strata, of a 

 compact feldspar are found interposed between the rows of pud- 

 dingstones and sandstones; and as they are less easily at- 

 tacked by the weather, they resist longer, and form elevated 

 ridges, such as the mountains of Sidlay, Ochiels, and Campsie, 

 which run in a chain from south-west to north-east, parallel 

 to the general direction of the formations, and to that of their 



