FLORIDA EEEFS. 35 



of paramount importance, were it only ^yitll reference to the position of 

 lighthouses. But there is another subject connected with this investiga- 

 tion which is not less momentous. It is well known that, in the Pacific, 

 coral reefs have been raised above the levels at which they were formed, by 

 the agency of the living animals, and also that in other localities, sometimes 

 in close connection with those just mentioned, the ground is subsiding. 

 These changes have been so often observed, whenever coral reefs occur, that 

 the idea of subsidence and upheaval is naturally connected with the features 

 of coral reefs, and the question at once arises, whether the reefs on our 

 shores are thus undergoing variations of level, independently of their 

 natural growth. We have seen how extensive are the changes produced 

 merely by the normal growth of the corals, and the facts accompanying 

 their increase. It now remains for us to ascertain whether this growth has 

 taken place, or does at present take place, upon ground which has 

 changed or is now changing its relative level in reference to the sea. 



The facts already described aiford a sufficient answer to the question. 

 We are satisfied that as far as coral formations have been observed upon the 

 main-land of Florida, and within the present extent of the coral reefs, no 

 change of the relative level has taken place either by subsidence or up- 

 heaval of the coral ground, and that all the modifications which the reef has 

 presented at successive periods have been the natural consequence of the 

 growth of reef-building corals, with the subsequent accumulation of their 

 products in the manner described above. 



I am sorry to differ from my friend, Mr. Tuomy, who, in an interesting 

 account of an excursion to Florida, considers the upright coral heads stand- 

 ing above the water level as evidence of the upheaval of the reef I have 

 already shown that, although at the first glance the position of these heads 

 suggests that they have grown where they are found, they are, in fact, 

 detached boulders, accumulated where thev now lie. Setting this aside, the 

 whole coral field of Florida furnishes connected evidence that neither up- 

 heaval nor subsidence of the ground on which the coral formations rest has 

 taken place. The maximum height of all these formations including 

 the bluffs on the main-land, is the same, — between twelve and thirteen 

 feet above high-water mark. If we ascribe their present level to a series of 

 upheavals rather than to the natural accumulation on the spot, we must 

 suppose each successive disturbance to have raised the more recent reef and 

 range of keys to exactly the same height as the earlier ones, without in the 



