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



binod, so as to produce a slight progressive swell, by which 

 objects are moved upwards and forwards, and then brought 

 back to their original position. 



One of the most distinct illustrations of this complex move- 

 ment, which is precisely similar to that of a ground-swell of 

 the sea, is afforded in the register, under date 31st December 

 1755, where it is mentioned that a person was first jolted to 

 the head of his bed, and then thrown back to where he lay 

 before. During the shock of August 1786, it is noticed, that 

 a person sitting on the ground, with his face to the west, felt 

 it heave up, first up under his right thigh, and instantly after 

 under his left. During the shock of 18th January 1809, a 

 gentleman riding recognised the noise, which was the usual 

 precursor of a shock. His horse stopped, and when the noise 

 was loudest, he distinctly felt the earth heave upwards and 

 undulate in a SE. direction. Here, also, the observation of 

 Sir Thomas D. Lauder, under date 13th August 1816, may 

 be referred to, as indicating not only a lifting of the ground, 

 but also a forward and next a retrograde movement of the 

 earth's surface. It must have been from this undulatory mo- 

 tion, that waves at the Kessock Ferry, perceived by persons 

 in a boat, were produced by the same earthquake. During 

 the shock of October 1821, an observer states, " I felt the 

 ground move under my feet, as if I had been on a piece of 

 moving bog." 



To these examples from Scotland, some from England may 

 be referred to. At Chichester, in 1707, as noticed in the re- 

 gister, there were distinct undulations of the surface, that 

 rolled in an E. and W. direction, causing beds standing N. and 

 S. to roll, and those standing E. and W. to pitch. The same 

 observation was made at Chichester in October 1731. In Lon- 

 don, which, as is shewn by the register, was severely agitated 

 by a shock on 8th February 1750, a person leaning on a desk 

 felt it first pushed up under one arm, and next under the other. 

 At another place near London, the ground, during the same 

 earthquake, though dry and solid, is described as having waved 

 like the surface of a river, and the tall trees bent their tops. 

 At Liverpool, in April 1750, a person compares the motion 



