1884.] NATURAL SCIENCES OF PHILADELPHIA. 189 



only material suitable for the manufacture of stone implements, 

 that the writer has seen in Florida. 



The coast is fringed with a strip of land four to six miles wide 

 that is low, level and rocky, from Cedar Keys to Anclote Key, 

 seventy-five miles farther south. 



A large portion of this land is swampy ; and much of it is 

 covered with water, when the tide is unusually high ; while the 

 highest portion of it is only 3 or 4 feet above the level of high 

 water. 



It is covered with a shallow, rich soil, which sustains a dense 

 growth of hard wood, in addition to many palmetto and red 

 cedar trees. 



At a distance of from eight to twelve miles apart small rivers 

 empty into the Gulf. They have their sources chiefly in large 

 springs, which are supplied by long, subterranean caverns. They 

 have cut crooked channels through the limestone rocks, not only 

 on the mainland, but through the shoals to the deep water of the 

 Gulf. 



These rocks, the foundation of the mainland, extend westward 

 under the water of the Gulf of Mexico ; and for the distance of 

 several miles from the shore great shoals exist ; making navigation 

 impracticable, except for small vessels. At low tide the rocks 

 are exposed to view in numerous instances, far from shore. In 

 fact such a great number of low islands exist along the coast, 

 separated from each other by shallow bays and creeks, that it is 

 difficult to determine what should be classed as the shore line. 



Many of these islands are overflown with water at high tide. 

 In such cases they are covered with mud : those nearest to the 

 sea usually sustaining a dense growth of mangrove trees ; while 

 others nearer the mainland are covered with saw-grass and bull- 

 rushes. 



A soft and unctious mud covers the bottom to the depth of a 

 few inches in the shoal water ; and an abundance of sea weeds 

 thrives there. These afl"ord shelter to vast numbers of mollusks, 

 crustaceans and worms, to the life of which those waters are well 

 adapted. 



The coast undoubtedly extended much farther into the Gulf, at 

 a time not very remote. On the bottom of the shoals and rivers, 

 and along the shores, the limestone rocks are eroded in a very 

 rough and uneven manner. No smooth surfaces are to be seen : 



