106 MESSRS. J. E. DAXYNS AND J. J. H. TEALL ON THE 



outlines under the microscope and the fact that they contain the 

 other constituents of the rock as inchisions. 'No doubt they have 

 been developed in situ. 



Andalusite is found in certain places to be a constituent of this 

 peculiar rock, and may with some confidence be attributed to contact- 

 metamorphism. This naturally suggests the conclusion that the 

 felspars are also the result of the same action ; but, as telling against 

 this view, we have to note that the felspathic character of the schist 

 is most pronounced at some little distance from the outcrop of the 

 plutonic rock, that it dies out westward as one approaches the 

 granite, and that nothing of the kind has been observed aloug the 

 sixteen miles of boundary extending from the Allt-na-Lairige west 

 of Meall nan Caora, down and across Glen Eine, and so round by 

 the southern margin to Garabal Hill. These difficulties in the way 

 of accepting the view that the felspathic schist is due to contact- 

 metamorphism may possibly be removed by taking into consideration 

 the varying character of the original rock, and the course of the 

 plutonic rock beneath the surface; but, as we have no further 

 evidence on these points, we must leave the question at present 

 undetermined. One other point may, however, be mentioned in 

 this connexion. The area occupied by this peculiar type of schist 

 is characterized by excessive folding. The detailed mapping of 

 certain well-marked bands along Troisgeach and the western side 

 of Ben Damhain has proved that actual inversion has been produced 

 in certain places. 



The prevailing structure of the plutonic rock is granitic, but at 

 one point on the north side of Loch Garabal, near the junction of 

 tonalite and schist, a gneissose structure may be observed. The 

 planes of foliation curve round included fragments, and the longest 

 diameters of the fragments correspond in direction with the general 

 trend of the foliation. There is no evidence that any portion of the 

 plutonic rock has been aifected by the earth-movements which have 

 operated so powerfully upon the schists, and we may therefore, 

 with much confidence, attribute the foliation in this case to move- 

 ments anterior to final consolidation. 



Taking all the facts into consideration, there seems no escape 

 from the conclusion that we have in this area the record of a series 

 of events connected with the consolidation of a vast subterranean 

 reservoir of molten rock. Having regard to the whole mass, it 

 seems probable that the process was a continuous one ; but if we 

 consider only certain limited portions it was unquestionably discon- 

 tinuous, for more acid material has frequently found its way, in 

 the form of veins, into already consolidated rocks of a more basic 

 character. The complex includes rocks which range in composition 

 from ultra-basic to acid. The ultra-basic rocks are represented by 

 wehrlites (olivine-diallage rocks), picrites (olivine-augite rocks), 

 serpentine (possibly representing dunites, saxonites, and Iherzo- 

 lites), and finally, a peculiar rock, to which it is difficult to give a 

 definite name, consisting essentially of enstatite, diallage, brown 

 hornblende, and biotite. 



