4 REPORT — 1892. 



cated to the Royal Society of tliis city, in the year 1785, the first outlines 

 of his famous ' Theory of the Earth.' Among those with whom he took 

 counsel in the elaboration of his doctrines were Black, the illustrious dis- 

 coverer of ' fixed air ' and ' latent heat ' ; Clerk, the sagacious inventor of 

 the system of breaking the enemy's line in naval tactics; Hall, whose fer- 

 tile ingenuity devised the first system of experiments in illustration of the 

 structure and origin of rocks; and Playfair, through whose sympathetic 

 enthusiasm and literary skill Hutton's views came ultimately to be 

 understood and appi-eciated by the world at large. With these friends, 

 so well able to comprehend and criticise his efi'orts to pierce the veil that 

 shrouded the history of this globe, he paced the streets amid which we 

 are now gathered together ; with them he sought the crags and ravines 

 around us, wherein Nature has laid open so many impressive records of 

 her past ; with them he sallied forth on those memorable expeditions to 

 distant parts of Scotland, whence he returned laden with treasures from 

 a field of observation which, though now so familiar, was then almost 

 untrodden. The centenar}^ of Hutton's ' Theory of the Earth ' is an 

 event in the annals of science which seems most fittingly celebrated by a 

 meeting of the British Association in Edinburgh. 



In choosing fi'om among the many subjects which might properly 

 engage your attention on the present occasion, I have thought that it 

 would not be inappropriate nor uninteresting to consider the more salient 

 features of that ' Theory,' and to mark how much in certain departments 

 of inquiry has sprung from the fruitful teaching of its author and his 

 associates. 



It was a fundamental doctrine of Hutton and his school that this 

 globe has not always worn the aspect which it bears at present ; that, on 

 the contrary, proofs may everywhere be culled that the land which we 

 now see has been formed out of the wreck of an older land. Among 

 these proofs, the most obvious are supplied by some of the more familiar 

 kinds of rock, which teach us that, though they are now portions of the 

 dry land, they were originally sheets of gravel, sand, and mud, which had 

 been worn from the face of long-vanished continents, and after being 

 spread out over the floor of the sea were consolidated into compact stone, 

 and were finally broken up and raised once more to form part of the dry 

 land. This cycle of change involved two great systems of natural 

 processes. On the one hand, men were taught that by the action of 

 running water the materials of the solid land are in a state of continual 

 decay and transport to the ocean. Ou the other hand, the ocean-floor is 



