A Yorkshire Rector of the Eighteenth Century. 15 



known as the Magnesian Limestone from its southern Umit 

 near the vale of the Trent, northwards along the margin of 

 the great coalfield and far into Yorkshire.* 



II. — The only contribution made by Michell to the dyn- 

 amical side of geological science is to be found in the Earthquake 

 paper already quoted which appeared in the Philosophical 

 Transactions of the Royal Society for 1760. f The memorable 

 Earthquake of ist November, 1755, which affected so vast a 

 region, directed general attention to the nature and cause of 

 such violent disturbances in the terrestrial crust. By far the 

 most original and important of the many contributions to 

 the investigation of this subject which at that time appeared, 

 was this Essay by Michell. In preparing it he turned to good 

 use the observations which, as we have seen, he had made 

 during various journeys and excursions from Cambridge 

 across the outcrops of the geological formations in the south 

 of England. He had obviously read widely in the literature 

 of earthquakes and had noted the characteristic phenomena 

 observed in them from ancient times to his own day. With 

 characteristic caution he did not pretend to have certainly 

 found their explanation, and he offered what he had to say on 

 the subject as ' conjectures ' only. The explanation which 

 he proposed postulated the existence of what he called 

 ' subterraneous fires,' to which water from above obtained 

 occasional sudden access. It was the general belief in his day 

 that such fires exist and are due to the spontaneous decom- 

 position and ignition of pyritous material in association with 

 inflammable substances such as coal and bituminous shale. 

 In the opinion of many of the leading naturalists of the time, 

 the existence of volcanoes was due to this underground ignition, 

 and the Wernerian geognosts went so far as to maintain that 

 volcanic action must be of comparatively late date in the 

 history of the globe, as, in their view, it could not arise until 

 after vegetation had long flourished on the surface of the 

 earth, and had in places been buried in coal-forming deposits 

 beneath sedimentary accumulations. 



* Michell's letter here quoted concludes with a pleasant proof of the 

 writer's friendship with Henry Cavendish and the members of the Royal 

 Society Club, to whom he sends his ' best respects ' and ' due compliments. ' 

 He also includes friends at the ' Cat and Bagpipes Club, ' which seems to 

 have been a company that included Cavendish and which met in a tavern 

 of that name at the corner of Downing Street. 



\ The title of this paper deserves to be given in full : ' Conjectures 

 concerning the Cause and Observations upon the Phasnomena of Earth- 

 quakes, particularly of that great Earthquake of the first of November, 

 1755, which proved so fatal to the City of Lisbon, and whose Effects 

 were felt as far as Africa, and more or less throughout almost all Europe. 

 By the Reverend John Michell, M.A., Fellow of Queen's College, Cam- 

 bridge.' 



1918 Jan. 1. 



