518 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [JlinO 6, 



anomaloas; but when we meet with the same spherical cavities 

 throughout the entire mass of the amygdaloidal beds over an area 

 many square miles in extent, it seems difficult to believe that the 

 beds in question could ever have been in motion like any ordinary 

 streams of molten rock. These and other considerations threw 

 doubt upon the apparently igneous character of the rocks under 

 review; and a careful examination of the district north of the 

 village of Ballantrae eventually revealed their truly metamorphic 

 origin. The coast-section north of Bennane Head first yielded what 

 are considered to be the proofs of this metamorphic action. The 

 same appearances frequently recurred in other places ; but a con- 

 densed description of the part of the coast-section alluded to will 

 perhaps suffice for the present. 



Between Balcreuchan Port and Port Yad a most interesting series 

 of rocks is laid bare. Distinctly bedded greywackes and shales 

 occur sporadically, but are quickly surrounded on all sides by con- 

 fused felspathic masses, for many of which we should require special 

 names. Pelspar-porphyries, felstones, amygdaloids, a remarkable 

 green rock stuck full of stones, and brecciiform masses which look 

 as if they had been violently pounded up in place are some of the 

 varieties we meet with. 



Succession of Changes'. — 1 a. Unaltered Strata. — The most un- 

 altered beds hereabouts are red, brown, and greyish sandy greywackes. 

 In places they are particoloured, showing yellow and green blotches, 

 owing to the decomposition of alkahne matter, with which all the beds 

 appear to be more or less charged. 



1 b. Slightly altered Strata. — The next beds to be noted are 

 more hardened, and often have a baked appearance ; they also con- 

 sist of greywackes — green, brown, red, and purplish blue. The dirty- 

 green beds are always highly magnesian and calcareous ; the grey 

 and brown beds less so ; the red beds still less so, often apparently 

 with no recognizable^ amount of alkaline matter. The same may be 

 said generally of the purplish-blue varieties, which, however, are 

 not of common occurrence along this part of the coast. All these 

 beds are much jointed, often to such an extent that they crumble 

 down into little angular fragments. This is markedly the case 

 with the compact red shales. The stratification is frequently contorted 

 and crumpled. 



2. Granular Strata with Vesicular Areas. — A little south of Bal- 

 creuchan Burn the greywackes upon the shore exhibit some very re- 

 markable appearances. These beds, although altered to some extent, 

 still show well-marked bedding, and are in places quite granular. 

 Little specks of a reddish-brown shale, similar to the small hardened 

 clay-galls in the greywackes of Peeblesshire, were occasionally de- 

 tected. The beds are felspathic, and have a greenish tinge from the 

 abundance of magnesian matter which they contain. Carbonate of 

 lime also enters somewhat largely into their composition. Completely 

 isolated and surrounded on all sides by this comparatively unaltered 

 greywacke occur several vesicular areas. The matrix of these areas 

 has the same general character as the rest of the beds, differing in 



