216 CORALS AND CORAL ISLANDS. 



formation ; while the deposit in deep water, consisting chiefly 

 of muddy lime particles, answers to his ' fades vaseux." 1 



"Double-Headed Shot Key is a long, crescent-shaped 

 ridge of rounded knolls, not unlike ' roches moutonneesj at 

 intervals interrupted by breaks, so that the whole looks like a 

 dismantled wall, broken down here and there to the water's 

 edge. The whole ridge is composed of the finest oolite, pretty 

 regularly stratified, but here and there like torrential depos- 

 its ; the stratification is more distinctly visible where the rocks 

 have been weathered at the surface into those rugged and 

 furrowed slopes familiarly known as ' karren ' in Switzerland. 

 It is plain that we have here the same formation as on Salt 

 Key, only older, with more thoroughly cemented materials. 

 The uniformity in the minute grains of the oolites leaves no 

 doubt that the sand must have been blown up by the wind, 

 and accumulated in the form of high dunes before it became 

 consolidated. The general aspect of Double-Headed Shot Key 

 is very different from that of Salt Key. The whole surface 

 is barren — not a tree, hardly a shrub, and the scantiest creep- 

 ing vegetation. The rock is very hard, ringing under the 

 hammer, and reminds one of the bald summits of the Jura, 

 such as Tete-de-Rang, near La-Chaux-de-Fond. It is evident 

 that what is beginning on Salt Key has here been not only 

 completed, but is undergoing extensive disintegration in 

 Double- Headed Shot Key, both by the action of atmospheric 

 agents over the surface, and by the action of tides and winds 

 against the base of the Ksy. 



"Among these older oolitic deposits, forming the main 

 range of Orange Key, and of Double-headed Shot Key, we 

 recognize formations of more recent date, occupying the cavi- 

 ties of ancient pot-holes, which have been gradually filled with 

 materials identical with those of the older deposits. The pot- 



