THE STRUCTURE AND AGE OF ARTHURS SEAT, EDINBURGH. 131 



10. On the Structure and Age of Arthur's Seat, Edinburgh. 

 By John W. Judd, Esq., E.G.S. (Read January 27, 1875.) 



Every geologist is familiar with the features presented by the 

 remarkable group of hills on the outskirts of the city of Edinburgh, 

 and is aware of the important part which their rocks have played in 

 the controversies of Neptunists and Plutonists, of Huttonians and 

 Wernerians. In discussing the origin of certain of the phenomena 

 presented at Arthur's Seat, and the evidence which these afford of 

 the period of its formation, it will be unnecessary to notice at length 

 the numerous important contributions to our knowledge of the 

 geology of the hill which are to be found in the works of the older 

 controversial writers *. Our retrospect of the previous literature of 

 the subject need not, indeed, go back further than the time of 

 Charles Maclaren, to whom is undoubtedly due the merit of demon- 

 strating that in Arthur's Seat and the surrounding hills we have the 

 relics of an ancient volcano. 



The results of Maclaren's patient studies and ingenious inferences 

 on the subject were given to the world in a series of letters in the 

 * Scotsman ' newspaper in 1834, and were embodied in his well- 

 known work ' The Geology of Eife and the Lothians,' published in 

 1839. I shall not be exaggerating the merits of this valuable and 

 original work in attributing to it a most important influence on the 

 progress of our science. The descriptions of Maclaren's work are a 

 model of accuracy and clearness ; and nothing can be more admirable 

 than the bold ingenuity, tempered by modest caution, with which 

 he traces out the causes to which the complicated structure of 

 Arthur's Seat owes its origin. 



Since the appearance of Maclaren's work a number of valuable 

 observations on the district have been published, especially by the 

 officers of the Geological Survey and by the members of the Geolo- 

 gical Society of Edinburgh. Foremost in importance among these 

 must be reckoned the proof, resulting from the accurate mapping of 

 the district, that the rocks of the Calton Hill are simply a portion, 

 separated by a fault, of the mass constituting the Arthur's-Seat 

 group t. 



The study of the structure of these hills suggested to Maclaren a 

 theory of their mode of formation which has been adopted, in all 

 its essential details, by Prof. Edward Forbes, Prof. Archibald Geikie, 

 and other observers. According to this theory, the rocks of Arthur's 



* It "will scarcely be right, however, to pass over this subject without a passing 

 reference to such names as those of Hutton, Playfair, Sir James Hall, Boue, 

 and Jameson, among the founders of geological science, or to those of Walker, 

 Williams, Townson, Allan, Ehind, Milne-Home, Hay-Cunningham, Dr. Hibbert, 

 Lord Greenock, and Professor Fleming among the students of the details of 

 Edinburgh geology. 



t See Memoirs of the Geological Survey : ' The Geology of the Neighbour- 

 hood of Edinburgh' (1861), p. 26. 



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