TRAXSACTIONS OF THE SECTIONS. 637 



Kyloe dyke was traced by Mr. Milne for about fifteen miles in a 

 direct line, towards the trap-hills of Home Castle. May not the 

 consideration just stated account for the direction of this dyke ? 



Another circumstance was noticed by Mr. Milne as a pro- 

 bable effect of the trap upon the incumbent strata, viz., the oc- 

 currence of indurated clay-beds, and even of chert, in the im- 

 mediate vicinity of it. At Carham there are thick beds of a 

 coarse gritty limestone, which contain abundance of quartz, of 

 a dusky brown and red colour. These beds of limestone are 

 themselves of a whitish cream colour ; and much indurated clay, 

 of the same colour, occasionally a little tinged with green or 

 red, accompanies them. These strata rest upon a porphyry, 

 which is in some places amygdaloidal, containing small grains 

 of quartz tinged with green earth. 



Near Dunse the same chert is again seen, but in strata of cal- 

 careous sandstone, which are of about the same thickness as 

 the limestone beds at Carham. They are here also immediately 

 incumbent on trap. At Newton Dony, at Marchmont, at Pres- 

 ton, and at Berwick the same indurated marls have been found, 

 which are sometimes so compact as to have been mistaken and 

 burned for limestone ; but which proved to be only marls har- 

 dened by their contact vrith, or vicinity to trap. 



The only other subject to which Mr. Milne adverted was the 

 changes which appear to have been produced on the surface 

 of the district, and on its elevation above the level of the sea, 

 at successive periods. 



Mr. Milne described at least four apparent elevations of the 

 land at successive periods : 1st, The elevation by which the 

 grauwacke strata were upraised ; 2ndly, The elevation by which 

 the old red sandstones were made to emerge from the waters 

 wherein they were deposited; 3dly, The elevation which con- 

 verted the marine strata of the coal-measures, or mountain 

 limestone of Northumberland, into dry land ; and, 4thly, a still 

 more recent elevation, the precise epoch of which has not yet 

 been exactly determined. 



It may, perhaps, throw light on the causes of these succes- 

 sive elevations to remember, that at the time when these for- 

 mations were respectively disturbed and elevated, trap-rocks 

 appear to have risen up, which at each successive outburst 

 most probably acted, not merely upon the particular group of 

 rocks among which they now protrude, but on the whole 

 district of country including the grauwacke range. These out- 

 bursts of ancient lava would most probably, like the cones on 

 the sides of a volcanic mountain, take place laterally, where the 

 resistance would be less than directly among and through the 



