296 Mr D. Milne on Earthquake-Shocks in Great Britain^ 



the morning of the shock, it had sunk to 28.63 inches, being a 

 subsidence of more than 1^ inch. 



During the earthquake of September 1801, it is mentioned 

 that " the barometer fell suddenly." 



On the 25th December 1821, there was a remarkable de- 

 pression of the barometer in every part of Europe. It was 

 noticed in Scotland, Germany, France, and Switzerland.* It 

 was accompanied with violent storms, with lightning and nume- 

 rous meteors. On the same day " a slight shock of an earthquake 

 was felt at Mayence.''* But what is more material, there was 

 at the same time a series of terrible eruptions in Iceland. The 

 old volcano of Eyefjeld Jokkul, which had been quiet since 

 1612, broke out on the 19th December 1821, and continued 

 in eruption till June 1822. In Iceland, the barometer began 

 to fall on the 18th December, and continued falling till the 

 26th December.t 



There was a shock of earthquake in Scotland in March 

 1831, and it will be seen that the barometer was lower during 

 the succeeding month than in any other of the same year. A 

 similar fact is recorded in the register, under date 20th March 

 1833. 



In the account of the Chichester earthquakes, in January 

 1834, the barometer is described as having been " in an inter- 

 mittent state" during the preceding month. 



The only other notices bearing on this point will be found 

 under dates 11th August 1786 and 1st November 1755. In 

 the last-mentioned case (viz. a depression of the barometer to 

 the extent of 2 inchesj at Amsterdam, during the Lisbon 

 earthquake), it is possible that the fall may have been occa- 

 sioned by an upward motion of the earth, which, owing to the 

 great inertia of mercury, would cause a flow into the cistern. 



* The amount of depression at different places will be found in the Edin- 

 burgh Philosophical Journal for 1822, vol. vi. p. 384 and vol. vii. p. 182. 



t Ditto, p. 156. 



I The following is the account given of this occurrence by the anony-' 

 mous author of the work so often referred to, entituled '* History and Phi- 

 losophy of Earthquakes," on p. 309. Among other phenomena at Amster- 

 dam he states, that " the mercury, which stood pretty high in the barome- 

 ters, descTunded almost an inch, as it were, at once," Othgr accounts repre« 

 scut the dcprcsaiou us greater. 



