474 Proceeding -"i of the Royal Irish Academy. 



the adjoinirig sub-metainoi'phic rocks became well-developed scliipts. 

 In the metamorphic area of the Castlebar district, county Mayo, it is 

 evident that, prior to the latest invasion of metamorphic action, there 

 Tvere intr'udes of granite, partly in masses and partly in ^de courses, 

 the last invasion changing these intrudes into a gTanitic-gneiss. 



The above suggestions and statements are, for the most part, solely 

 confined to the effects due to regional metamoi-phism, unaided by 

 either of the other kinds. It must, however, be remembered that 

 such a supposition can be solely provisional, as the majority of the 

 intrudes of eruptive rocks had, as adjuncts, tracts of rocks affected by 

 contact metamorphism ; while certain rocks, if raised sufficiently near 

 or to the earth's surface, must have come under the influence of 

 methylitic action ; while all rocks, in any way changed by either of 

 these actions, must more or less influence any subsequent regional 

 metamorphism, and thereby introduce numerous complications — a sub- 

 ject of such extent that it cannot here be entered on. 



