MR MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 449 



and that occasionally red rocks are seen lying above these, I think can also be 

 affirmed. But there is no reason to believe, that these several classes of rocks 

 form separate and independent formations. They appear rather to be all mem- 

 bers of the same formation, deposited, however, under not exactly the same cir- 

 cumstances. The appearance of red sandstone strata among, and even above, the 

 carboniferous strata, may be explained by supposing, that the causes which had 

 previously led to so large and constant a deposition of red sandstones, though 

 diminished, had not altogether ceased. At various places in the county, the old 

 red formation can be seen passing into the coal-measures, by a blending and in- 

 termixture of the strata characteristic of both. Thus, in Mellenden Burn (two 

 miles south-east of Kelso), there are beds of red shales and calcareous marls and 

 sandstones, including beds of conglomerate which contain porphyry pebbles. In 

 Sunlaws quarry, on the Teviot opposite to Roxburgh, there will be seen red sand- 

 stone strata, overlaid by blue and brown marly strata. 



II. Unstratified or Igneous Hocks. 

 These I divide into three classes, 

 1st, Felspathic rocks. 

 2d, Tuff or amygdaloidal rocks. 

 3d, Augitic and hornblende rocks. 



Of these three classes, the first is by far the most extensive and remarkable ; 

 in proof of which, it is only necessary to mention, that the Cheviot and Eildon 

 Hills, as well as many others in the county, belong to it. 



In each of these classes, two epochs of eruption are apparent, judging by the 

 effects produced on the contiguous stratified rocks. 



In describing these several sets of igneous rocks, I shall endeavour to indicate 

 their ages by a reference to this test. 



1. The Felspathic Rocks present, generally speaking, various shades of a yel- 

 low, and sometimes reddish-brown colour. Occasionally they present purple and 

 lilac hues. They form rounded and dome-shaped hills, very different from the 

 elongated and occasionally precipitous greywacke hills. 



(1.) Following the division above explained, as to the age of these rocks, I 

 observe, that the Cheviot and Eildon Hills appear to have been formed at an era 

 prior to the deposition of the old red sandstones, as these stratified rocks are, in 

 many places, some of which will be immediately mentioned, seen close to the fel- 

 spar rocks, without exhibiting any change either of dip or of texture. 



VOL. XV. PAKT III. 6 F 



