British Pillow-lavas. 243 



Cornwall were being poured out, eruptive centres in Cumberland 

 were emitting hypersthene andesites and other rocks of Pacific type : 

 on the other hand, in the Lower Carboniferous period, spilites and 

 quartz-keratophyres were the characteristic lavas of Devonshire and 

 Cornwall, while trachytes, phonolites, olivine-basalts, teschenites, 

 and nepheline-basalts of Atlantic facies were the dominant igneous 

 rocks of East Lothian in Scotland. 



In 1899 Teall (25) remarked that "it is interesting to note that 

 at Ballantrae in Cornwall and in Mont Genevre diabasic lavas with 

 pillow-structure occur in the immediate neighbourhood of gabbro 

 and serpentine, and that in all three localities some difficulty is 

 experienced in determining the precise relations of these rocks". 

 The constant association of diabase (spilite), serpentine, and gabbro 

 in the northern Alps with radiolarian cherts has led Steinmann (37) 

 to regard these ' ophiolitic eruptives ' as the typical volcanic rocks 

 •of abysmal depressions. Suess has accepted and extended this 

 hypothesis, considering the ' green rocks ' to be injections into folded 

 ranges associated with dislocations, but not invariably with deep-sea 

 conditions (38). The ' ophiolitic eruptives ' of Steinmann are hot 

 coextensive with the spilitic suite of igneous rocks as here defined, 

 and still less so are the ' green rocks ' of Suess. In several parts 

 of Britain the association of gabbro and serpentine with spilitic lavas 

 is difficult to explain as a mere accident, but we have not been able to 

 establish definitely, in those parts of Cornwall or of Scotland with 

 which we are personally familiar, that the one series is the 

 plutonic representative of the other. For the present we prefer to 

 regard this as an open question, hoping to return to its consideration 

 at some future time. 



The Adinoles. 



That t)pe of alteration by which shales and slates are converted 

 into adinoles has been produced by basic intrusive rocks of more 

 than one class. In the Lothians, for example, it occurs at the 

 margins of some teschenite sills, and quartz-diabases sometimes also 

 induce it. But there can be no doubt that the albite-diabases that 

 belong to the spilite suite of igneous rocks are more efficient in 

 changing shales to adinoles than ail the other kinds of diabase. 

 In Cornwall and Devon adinoles occur with great frequency both 

 in the Devonian and Culm, and the adinole of Dinas Head is 

 especially well known through the descriptions of Fox and Teall and 

 the analyses of Hort Player (40). We may further remind our 

 readers that an extensive literature has been written about the 

 similar rocks of the Rhine district, which also occur in contact 

 with the late Devonian and early Carboniferous intrusive sills that 

 belong to the spilitic volcanic series. 



The adinoles in their highest development are nearly pure albite 

 rocks. No shales have a similar composition, for none are so rich 

 in alkalies, yet the transformation of a shale into an adinole often 

 takes place within a few inches. Hence there is no escape from 

 the conclusion that there has been an infusion of new substances, 

 principally soda, into the sediment, and this has been generally 



