284 ME. E. B. BAILEY ON THE [June 1913, 



Mr. Symes had a similar experience [8, p. 62], for he met with an 

 epidiorite outcrop, which he described as follows : — 



' The first few feet of this sill lying next to the dark slates present a highly 

 vesicular and amygdaloidal texture. . . . Where the kernels have weathered out 

 the rock is so cellular as closely to resemble a lava, which the rock may possibly 

 have been.' 



This observation was made in 1899, and its record constitutes 

 the first published expression of opinion that volcanic rocks may 

 exist in the district. I believe that it is fair to assign no small 

 share of the credit of this observation to Dr. Peach. 



It was presently found that this vesicular epidiorite was not an 

 anomaly: for two years later Dr. Peach, the late Mr. Grant Wilson, 

 and Mr. Maufe found it convenient to group the epidiorites of the 

 large district lying between Loch Avich and Crinan Loch into two 

 types — both types, as was the custom of the time, regarded as 

 intrusive [12, p. 129]. One type is 



' a fine-grained rock, slaggy and highly vesicular at its margin, sometimes 

 showing an arrangement of phacoids with vesicular outer layer and a non- 

 vesicular interior suggestive of the " pillow-structure" visible in certain lava- 

 flows. Sills of this rock are usually associated with phyllites and limestones, 

 and apparently produce little or no metamorphic action upon the neighbouring 

 sedimentary rocks.' 



This absence of special metamorphism due to contact-alteration 

 in the sediments accompanying the ' lavaform epidiorites ' is a 

 significant fact ; for the regional metamorphism of the district is 

 of so low a grade that contact-alteration accompanying the coarse- 

 grained epidiorites is often very conspicuous. It was, of course, 

 because many of the epidiorites of the region are obvious intrusions 

 that there was such reluctance to admit that any of them might be 

 lavas. 



Although Dr. Peach and his collaborators did not re-examine 

 the ground, it is not surprising to find them, in the memoir which 

 appeared in 1909 [17, pp. 43, 45], expressing the opinion that, in 

 the light of the Tayvallich evidence, some of the epidiorites should 

 be regarded as true lavas. In support of this, Mr. Maufe published 

 a very convincing sketch from his notebook of one of the vesicular 

 sheets, showing well-defined pillow-structure [17, fig. 5, p. 45]. 



Turning eastwards, we encounter similar evidence, for in 1900 

 Mr. Hill met with highly vesicular epidiorites in the neighbourhood 

 of Loch Awe. After describing a typical development of these rocks 

 near Inverliver, he adds : — 



' Mr. Teall has pointed out the resemblance of these unaltered rocks to the 

 volcanic accompaniments of the Lower Silurian radiolarian cherts in the South 

 of Scotland and elsewhere.' [S, p. 42.] 



Dr. Flett has of late greatly added to the significance of this 

 comparison of Dr. Teall's, for he lias extended it to include the 

 lava-types of the western region already mentioned [17, pp. 50-56], 

 and also of the Tayvallich country itself [18, pp. 84-90 ; see also 

 19]. Dr. Flett has furthermore expressed the opinion that the 

 coarsely - crystalline intrusive epidiorites must be regarded as 



