1012 REPORT—1885. 
a more complex and difficult character. Especially in this connection do we 
welcome such contributions to our knowledge as that made by Mr, Teall in his 
description of the remarkable foliated dyke of Scourie. 
Very significant indeed is the fact that the phenomenon of foliation appears to 
be confined to regions which haye been the scene of the most violent subterranean 
movement and disturbance. That solid rock-masses, subjected to the tremendous 
earth-strains to which they are liable during mountain-making, are capable of 
internal movement and flow—like the ice of a glacier—we have the clearest evi- 
dence. Many illustrations might be adduced in support of the view that crystal- 
lisation is influenced and controlled by mechanical forces—pressures, stresses, and 
strains. May it not also be true, as long ago suggested by Vose, that the heat 
which must be generated in the great shearing movements taking place in rocks 
have also had much to do in giving rise to that re-crystallisation which is the 
essence of foliation? Rock-masses, in the throes of mountain-birth, have, like 
glaciers, behaved substantially as viscous bodies; may not the former have under- 
gone molecular changes analogous to regelation in the latter ? 
That many of the stupendous earth-movements which produced the foliation of 
the rocks of Scandinavia and the Scottish Highlands must be referred to Archean 
times, there is not the smallest room for doubt. That similar effects have resulted 
from the same agencies during subsequent periods, our fellow-geologists in Scan- 
dinayia believe they have found incontrovertible proof. For my own part I look 
forward confidently to the establishment of the same conclusion from the study of 
our own Highland rocks. 
But here I am conscious that I am venturing on topics upon which great and 
allowable differences of opinion still exist. The debates in this Geological Section 
during the-first meeting of the British Association in Aberdeen ought, I think, to 
have marked the practical close of one great series of controversies. ‘The discussions 
of the present meeting will, I trust, result in the recognition and clear statement 
of a number of other equally important problems of Highland geology which still 
await solution. And Iam sanguine enough to hope that when this Association 
next gathers here, my successor in this chair will have to congratulate his audience 
upon a very brilliant retrospect of work actually accomplished in the interval. 
I am encouraged in this optimism by the fact that in the period which has 
elapsed since our last meeting here, great and important improvements have been 
made in the methods of geological investigation. We have seen how the discovery 
of a few fragmentary shells in the limestone of Durness, and of sundry casts of hones 
in the sandstone of Elgin, have been the means of profoundly modifying our ideas 
concerning the age of vast tracts of rock in the Highlands. The development of 
modern methods of petrographical research is destined, I believe, to lead to a similar 
revolutionizing of our views concerning the wonderful series of changes which have 
taken place within rock-masses, subsequently to their original accumulation. 
Especially does the application of the microscope to the study of rocks, when 
employed in due subordination to, and illustration of, work done in the field, pro- 
mise to be the source of valuable and fruitful discoveries in the field of Highland 
geology. 
In cbanastilie with this subject, I cannot refrain from reminding you that while 
the initiative in the application of the paleontological method of research was taken 
by an English land-surveyor, we are indebted to a Scotchman in an equally lowly 
station of life, for overcoming some of the first difliculties in connection with petro- 
graphical study. Many microscopists had employed their instruments, and some- 
times with useful results, in the study of the powders and the polished surfaces of 
rocks; but it is to William Nicol of Edinburgh, the inventor of the well-known 
polarising prism which bears his name, that we owe the discovery of the method of 
preparing transparent sections of fossils, crystals, and rocks, whereby their internal 
structure may be examined by transmitted light. Nicol bequeathed his prepara- 
tions to his friend Alexander Bryson, and some of them are now preserved in the 
British Museum. It is interesting, too, to recall the circumstance that it was a thin 
section of the granite of Aberdeen in the collection of Bryson which exhibited to 
