EARLY SCOTTISH GEOLOGISTS 159 



Lingering for a moment over these local associa- 

 tions, we shall find a peculiar appropriateness in the 

 time of this renewed visit of the Association to 

 Edinburgh. A hundred years ago a remarkable group 

 of men was discussing here the great problem of the 

 history of the earth. James Hutton, after many 

 years of travel and reflection, had communicated to 

 the Royal Society of this 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 

 discoverer of c fixed air ' and ' latent heat ' ; Clerk, 

 the sagacious inventor of the system of breaking the 

 enemy's line in naval tactics ; Hall, whose fertile in- 

 genuity 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 appreciated by the world at 

 large. With these friends, so well able to compre- 

 hend and criticise his efforts 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 im- 

 pressive 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 

 centenary of Hutton's Theory of the Earth is an event 

 in the annals of science which seems most fittingly 



