EARTH OSCILLATIONS. 345 



quakes in a paroxysmal manner have already been men- 

 tioned. The movements referred to in this chapter, al- 

 though generally taking place with extreme slowness, in 

 certain instances, by an increase in their rapidity, have 

 approached in character to earth pulsations. In most 

 instances it would appear that the upward movement of 

 the ground, which may be likened to a process of tumefac- 

 tion, goes on so gently that it only becomes appreciable 

 after the lapse of many generations. 



Examples of movements. — Lyell estimated that the 

 average rate of rise in Scandinavia has been about two and a 

 half feet per century. At the North Cape the rise may have 

 been as much as five or six feet per century. Observations 

 made at the temple of Jupiter Serapis, between October 

 1822 and July 1838, showed that the ground was sinking 

 at the rate of about one inch in four years. Since the 

 Koman period, when this temple was built, the ground has 

 sunk twenty feet below the waves. Now the floor of the 

 temple is on the level of the sea. Lyell remarks that if 

 we reflect on the dates of the principal oscillations at this 

 place there appears to be connection between the move- 

 ments of upheaval and a local development of volcanic 

 heat, whilst periods of depression are concurrent with 

 periods cf volcanic quiescence.* 



As examples of movements even more rapid than those 

 at the Temple of Jupiter Serapis we refer to an account 

 of the earthquakes in Vallais (November 1755), when 

 the ground about a mountain at a small distance from 

 Brigue sank about a thumb's-breadth every twenty-four 

 hours. This took place between December 9 and Feb- 

 ruary 26.^ 



Another remarkable example of earth movement is 



* Principles of Geology, vol. ii. 177. 



* Gent. Mag., vol. xxvii. p. 448. 



