28 MR. E. H. CUNNINGHAM-CRAIG ON [Feb. I904, 



EXPLANATION OF PLATES II- V. 



[With the exception of fig. 2 in PI. V, photographed under a g-inch objective, 

 all the slides are represented as viewed under a 1-inch objective.] 



Plate II. 



Fig. 1 (8983). Schistose grit from Craignahuiilie, which shows the breaking- 

 down of a large quartz-pebble in a schistose but non-crystalline 

 matrix. (See p. 10.) 

 2 (8987). A highly-quartzose schist from Inveruglas, in which allothigenic 

 structures have been completely destroyed. It shows recrystallized 

 quartz and authigenic muscovite. A vein of calcite, derived from 

 crushed felspar, is seen on the right. (See p. 19.) 



Plate III. 



Fig. 1 (8984). Schistose grit from Eudha Mor, showing a large quartz-pebble, 

 partly granulitized, in a matrix rich in authigenic biotite. 

 2. The same under crossed nicols. (See p. 17.) 



Plate IV. 



Fig. I (8990). A typical albite-gneiss from Eudha Ban, very highly crystalline. 

 It contains albite, quartz (recrystallized in lenticles), chlorite (abun- 

 dant), muscovite, and pyrites. (See p. 21.) 

 2. The same under crossed nicols. 



Plate V. 



Fig. 1 (8992). This shows the effects of contact-metainqrphism on an albite- 

 gneiss from Ardlui. There is a finely-crystalline development of 

 biotite and white mica, with quartz recrystallized in lenticles, but 

 albite and chlorite are absent. (See p. 26.) 

 2. The same, more highly magnified : showing the granular development of 

 andalusite. 



Discussion. 



Mr. H. M. Cadell said that the completion of this map interested 

 him greatly, as it had been some 25 years in progress and was 

 happily out at last, to the great advantage of Scottish geologists, 

 who had awaited it for nearly a generation. He had worked on 

 the western part some 18 or 19 years ago, and the Author had 

 worked out the structure in much greater detail and with the aid 

 of the microscope, which was not so much in vogue when he was 

 there, the consequence being that the Author had greatly modified 

 part of his (the speakers) results. He was glad of this, as geology 

 was, and should be, a progressive science. He would like the Author 

 to say what became of the limestones that occurred among the 

 slates south of Luss, as these passed northward into the more 

 highly-metamorphosed area ; also what, if any, was the nature of 

 the contact-metamorphism round the granite and diorite-intrusions 

 north of Arrochar ; and further, whether the Author knew the source 

 of the ilmenite which occurred in considerable quantities in that 

 locality. 



The Chairman (Sir Aechibald Geikie) spoke of the early work of 

 the Geological Survey in the Loch-Lomond district, and the difficulty 

 that was experienced there in making out the order of succession of 



