212 The Scottish Nattiralist. 



will take the matter up, and that ere long through their labours 

 our knowledge of post-glacial Scotland will be greatly increased. 



Before closing this address, I should like to say a few words to 

 the geologists of the Union. The mapping-out of the various 

 rock-masses and geological formations of the east of Scotland by 

 the Government Geological Survey is now far advanced, so that 

 we are saved the labour of producing reliable geological - maps. 

 But the mere mapping-out of the rocks does not, by any means, 

 leave nothing for the local geologists to accomplish. Many diffi- 

 cult problems will still remain for solution. The question of 

 metamorphism, for example, is one which will long remain open ; 

 and each of us may do something towards explaining the origin of 

 our crystalline schists by careful detailed examination of the rocks 

 in the field, and by subsequent critical study of them under the 

 microscope. The phenomena of the igneous rocks of the east of 

 Scotland also afford a wide field of study, and one which the 

 labours of the Geological Survey will certainly not exhaust. The 

 petrological examination of these rocks, as my friend Mr. Durham 

 in his Report remarks, will well repay the observer. An adequate 

 study of the igneous rocks of the Sidlaws, for example, which I 

 mapped for the Survey, would entail many long years of assidu- 

 ous labour. It would be well, also, for local geologists to note 

 every new exposure of rock, especially such sections as tend to 

 modify the boundary lines upon the maps of the Geological Sur- 

 vey. Notice of these new exposures should then be sent to the 

 Geological Survey Office that the necessary corrections of the 

 maps may be made ; for it is clearly in the interests of all that 

 the work of a great Government Survey should be as perfect and 

 complete as it can be made. With regard to the glacial and post- 

 glacial deposits, we have still, as I have said, much to learn. 

 The main features of glacial history as at present known, are not, 

 I think, likely to be much modified. That the till or boulder-clay 

 is the moraine profo?ide of an extensive ice-sheet seems to me as 

 well proved as we can expect any fact in geological history to be. 

 That the Glacial period consisted of an alternation of cold and 

 genial epochs has also, I think, been demonstrated both for Europe 

 and North America. But when we come to the deposits pertain- 

 ing to late glacial times, to those, namely, which were laid down 

 when the great glaciers of the Ice-age proper were slowly melting 

 away — we encounter phenomena which have been variously ex- 



