35 



streams of volcanic matter were poured out from the heated interior. 

 These spread out among the beds in sheets, pierced them through 

 n dikes, and were accumulated over them in great mountain masses. 

 The succeeding revolutions by which the existing aspects were 

 ^iven to the surface have been briefly sketched in the preceding- 

 part of these notices. 



26. With regard to the distribution of these igneous products 

 .t is remarkable that they have been chiefly erupted along the 

 Doundary of the Devonian and carboniferous rocks, from Ardrossan 

 ;o the mouth of the Eden, in the Coast Range, the Lennox, Ochill, and 

 Jidlaw hills, so nearly continuous with one another, as to be sepa- 

 ated only by the channels of the Clyde, Forth, and Tay. This 

 ine is parallel to the principal axis of the Grampians, which were 

 elevated at an earlier period ; and is also in the direction followed 

 >y the many earthquake movements recently experienced in Scot- 

 and. There is also evidence of elevatory movements in connection 

 vith another band of these rocks near the border of the primary 

 Highland tracts.* On the south border of the coal districts there 

 s also an extensive development of these rocks ; and they constitute 

 everal considerable ranges within the area, as the Fereneze and 

 ^athkin hills separating the Ayrshire fields from those of Lanark 

 ,nd Renfrew, the Bathgate hills, and other lesser ridges. The 

 iuge trappean mass of Tinto, and the varied igneous products of 

 he Pentlands seem to belong to an older era. That the trap 

 anges on the borders, and within the area, were erupted since the 

 leposition of the coal strata is shown by many facts. Along the 

 )ase of the Cathkin hills, in the glens near Barrhead and Neilston, 

 ind in natural sections among the Gleniffer hills, the coal strata 

 aay be seen gradually raised to a high dip, set on end, and finally 

 eversed when in contact with the trap. The Coast Range of old 

 ed sandstone from Ardrossan to Port-Glasgow, through which 

 he Clyde has forced a passage between Bishopton and Dumbuck is 

 >verlaid throughout by trap rocks. These cover also the eastern 

 lopes, and come in contact with the coal strata, which are over- 

 opped by and disappear beneath them. Similar phenomena have 

 ieen already noticed in describing the Campsie district. The case 

 igured in the cut of Art. 12 is very interesting. The great stream of 

 asaltic matter intruded into the coal strata, encloses a shale bed, c, 

 fhich has been altered through a considerable distance to the state 

 f a coarse opal. The sandstone also in the river bed adjoining con- 

 ains crystals of galena in close proximity to the trap. The changes 

 * Journal Geolog, Soc., 1852. 



