XIII.] SLOW MOVEMENTS OF THE LAND. 209 



sloping sides until they reached the general level. In fact, 

 the freedom of motion which the liquid molecules enjoy 

 renders it impossible to produce anything like a hump of 

 water, except temporarily. As soon as the surface of the 

 liquid is raised at one point, it tends to fall down again 

 until a common level is restored. Hence if the sea rose, 

 and kept its high level around the bases of the columns, the 

 rise could not have been confined to the Bay of Naples, but 

 must have been part of a general rise of the surface of the 

 ocean, to the same extent, all over the world. The difficulty, 

 however, of finding a source for so vast an amount of 

 additional water, as this general rise would imply, is 

 alone an insuperable objection to this hypothesis. But 

 geologists have abundant other reasons for the conclusion 

 that, in such cases, it is the land and not the sea that has 

 shifted its level. 



It appears then that the marks left by the boring shell- 

 fish on the columns of the temple of Serapis, upwards of 

 twelve feet above sea-level, prove that the land on which 

 these pillars stand must, at one time, have been depressed 

 to that extent, and afterwards elevated to its present posi- 

 tion. But the temple teaches much more than this. About 

 five feet beneath the present marble floor of the build- 

 ing, there are the remains of another floor ; and it 

 seems only fair to suppose that the upper pavement 

 was constructed after the lower one, which belonged to 

 some earlier building, had been carried down to an in- 

 convenient level by subsidence of the land. Such sub- 

 sidence has indeed been going on in this locality within 

 tlie present century ; for, when the ruins were first un- 

 earthed, the upper floor stood much higher than it stands 

 at present. Careful observations, in the early part of this 

 century, showed that the ground was sinking at the rate 



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