<-.] THE LIME IN THE MORTAR. 121 



stones of these isles save and except the difference in 

 every shell and coral which you would not see in the 

 coral-beds of the West Indies, if such earthquakes as 

 that famous one at St. Thomas's, in 1866, became 

 common and periodic, upheaving the land (they needs 

 upheave it a very little, only two hundred and fifty 

 feet), till St. Thomas's, and all the Virgin Isles, and 

 the mighty mountain of Porto Rico, which looms up 

 dim and purple to the west, were all joined into dry 

 land once more, and the lonely coral-shoal of Anegada 

 were raised, as it would be raised then, into a limestone 

 table-land, like that of Central Ireland, of Galway, or 

 of County Clare. 



But you must clearly understand, that however 

 much these coralline limestones have been upheaved 

 since they were formed, yet the sea-bottom, while they 

 were being formed, was sinking and not rising. This 

 is a fact which was first pointed out by Mr. Darwin, 

 from the observations which he made in the world- 

 famous Voyage of the Beagle ; and the observations of 

 subsequent great naturalists have all gone to corrobo- 

 rate his theory. 



It was supposed at first, you must understand, that 

 when a coral island rose steeply to the surface of the 

 sea out of blue water, perhaps a thousand fathoms or 

 more, that fact was plain proof that the little coral 

 polypes had begun at the bottom of the sea, and, in 

 the course of ages, built up the whole island an 

 enormous depth. 



But it soon came out that that theory was not 

 correct ; for the coral polypes cannot live and build 

 save in shallow water say in thirty to forty fathoms. 

 Indeed, some of the strongest and largest species work 



