106 SPOLIA ZEYLANTCA. 



the foliated crystalline rocks of Ceylon as granulites, and as 

 belonging to the charnockite series of Ceylon and Southern 

 India. 



With regard to the use of the term " metamorphic series," it 

 should be recognized that the evidence tends to show that the 

 mass of Ceylon rocks is rather conspicuous for the small evidences 

 of metamorphism subsequent to formation which it affords. The 

 term " metamorphic," embodying as it does a very definite 

 and, generally speaking, erroneous view, is thus to be avoided. 



If we come to inquire as to the real nature of the rocks composing 

 the granulite or charnockite series, we are at first struck by the 

 appearances in the field suggestive of a sedimentary origin (figs. 

 1 and 2). It is not surprising that the conspicuous bedded charac- 

 ter, varied mineral composition, and local abundance of alternating 

 beds of limestone should have led to the supposition that such a 

 gneissose series as we have here to deal with really represents the 

 highly metamorphosed remains of some ancient sedimentary series. 

 Closer examination of the rocks, however, reveals but little in 

 support of such a view. Their mineral composition is found to 

 indicate a chemical constitution differing in important respects 

 from, that of the great majority of sedimentary rocks, but similar 

 to that of many well-known types of deep-seated igneous rock. 

 Moreover, when we come to examine the minuter characters of 

 the foliation or mineral banding so characteristic of the Ceylon 

 rocks, we see that there is rather a lenticular than a definitely 

 parallel structure (fig. 2), and also that some definite relation 

 is evident between the lighter-coloured (more acid) rock types and 

 those of a darker colour — the more basic. 



This definite relationship may show us ovoid lenticular masses 

 of heavy dark rock included in a much lighter-coloured, more 

 acid rock that seems to have flowed around them. In other cases 

 the more acid types give other evidence of their intrusive relation 

 to the more basic bands and lenticles. When the rock examined 

 possesses a general dark colour and basic character we often find 

 the more acid portions existing as irregular patches a few inches 

 or feet in diameter, which send long tongues of acid material 

 in parallel bands along the foliation planes, giving a banded 

 character to a rock which would otherwise present a more 

 uniform appearance. Such phenomena, together with others 

 which a microscopic examination of the rocks reveals, are known to 

 be characteristic of many rocks whose igneous origin is undoubted. 

 It may then be assumed with safety that at least the greater part 

 of Ceylon rocks, f?o far as at present known, are of igneous 

 origin and that their well-baudtnl appearance (fig. t) results 



