306 Mr D. Milne on Earthquake-Bhockt in Great Britain^ 



vantageous to point out some of the inferences which appear 

 to be established by the register, so far as it goes, and the phe- 

 nomena embraced by it. 



(1.) Whilst it is undeniable that the shocks emanate from the 

 interior part's of the earth at different depths, it would appear 

 that they are essentially connected with changes in the earth's 

 atmosphere. This inference is established by the proofs ad- 

 duced in the foregoing pages, of the various meteorological 

 phenomena that almost constantly attend earthquake-shocks. 



In what way these atmospheric changes are connected with 

 earthquakes, — v/hether as causes or effects of them, — is a dif- 

 ferent question. Some of them, it may be thought, cannot 

 possibly be considered effects. For example, the monthly va- 

 riations in the weight and electricity of the atmosphere (to 

 which the monthly occurrence of earthquake-shocks exactly 

 correspond), no one will venture to ascribe to any other than 

 solar influence. If, then, none of these are the effects of earth- 

 quakes, is it to be at once concluded that they are the causes, 

 or that they influence the causes, of earthquakes % Do all of 

 these meteorological forces, or atmospherical conditions, exert 

 an influence, — and do they act separately or in combination ? 



Mr Scrope, in his excellent treatise on Volcanoes says, that 

 he was told by the Lipari fishermen, that the intensity of the 

 eruptions at Stromboli is much greater during winter than 

 summer, and that it usually increases with the storminess of 

 the season, insomuch that the fishermen are in the habit of 

 auguring fair or foul weather from the state of the volcano. 

 This circumstance, which is entirely in accordance with the 

 facts deduced from our register, led Mr Scrope to suggest, that 

 the greater frequency of earthquake-shocks in the winter sea- 

 son may be owing to the diminution of atmospherical pressure 

 during that season.* When the barometer is at 31 inches, 

 the atmosphere presses on the surface of Great Britain with a 

 weight equal to 291,793,239,406 tons. When it sinks to 27 

 inches, there is a diminution of weight on the same area, equal 

 to 37,648,938,386 tons, being about 427,231 tons on each 

 square mile. It is manifest, that, when the subterranean elas- 

 tic forces have, by accumulation or otherwise, acquired such 



* Scrope on Volcanoes, p. 7 and 60. 



