276 Mr Richard Edmonds on Earthquakes 
were actually felt in this island, and the waters of our ponds 
agitated, at the very time when some of the oscillations of the 
sea were taking place ; which seems almost to establish the 
fact, that such oscillations are produced by local submarine 
shocks. I may also mention that in 1788, the sea at Dunbar 
suddenly receded a foot and a half on the day that a shock 
was experienced in the Isle of Man.* So also a shock was 
felt in Perthshire on the 10th of March 1842, and on the fol- 
lowing day a disturbance of the sea (the effect, probably, of 
another shock) took place in the western isles of Scotland : 
and it has been observed in Perthshire that “ shocks seldom 
oceur single,”—but “come very frequently in groups.’’} 
Mr Milne, however, thinks that the oscillations of 1843 
may have been produced “ partly by the mechanical pressure 
of the wind in the storm,—blowing first in one direction, and 
thereafter in an opposite direction,—and partly by the sud- 
den diminution of atmospheric pressure accompanying its 
progress,” t without the intervention of submarine shocks : 
and he brings forward numerous examples to shew that such 
agitations are usually preceded or attended by violent storms 
or other proofs of great atmospheric disturbance: but these 
examples are quite as favourable to my hypothesis as to his 
own ; for they are equally applicable to earthquakes which 
have often occurred during storms and hurricanes.§ The 
first earthquake which Humboldt felt at Cumana was 
during a severe thunder storm. “At the moment of the 
strongest electric explosion there were two considerable 
shocks of an earthquake.”|| And the excessive minima of 
the barometer which have been observed during oscillations 
of the sea have been also observed at the times of earth- 
quakes :—thus Humboldt, on a certain occasion, observed 
* Jameson’s Edinburgh Philosophcal Journal, July 1841, p. 108. 
t Ibid., October 1841, p. 286. 
t In Cornwall and Devon the fall of one inchin the barometer corre- 
sponds with the rise of sixteen inches in the level of the sea, and vice 
versa.—Hdin. R.S. Trans., vol. xv. pp. 635-637. 
§ Jameson’s Edinburgh Philosophical Journal, 1841, pp. 294-297. 
|| Personal Narrative, vol. iii. p. 316. 
