AGASSIZ: THE FLORIDA ELEVATED EEEF. 53 



locality the rise is gradual, commonly from a coastal swamp (Plate XX.). 

 Inside of Key Largo the coastal swamp is ten or twelve miles wide. 

 The oolite rises to an elevation of about twenty feet, and then main- 

 tains a generally level surface, with the exceptions of occasional broad 

 undulations, having axes about east to west or north to south, and sinks. 

 The hollows of the broad undulations are filled with water during the 

 rainy season, so that pines do not grow in them ; in the dry season grass 

 grows luxuriantly, and some of the sinks are cultivated. Some soil has 

 accumulated in these " prairies," whereas among the pines there is 

 scarcely any soil to hide the jagged rock surface and loose fragments 

 (Plate XXI. Fig. 2). The sinks are sometimes of rounded form, with 

 perhaps a maximum diameter of two hundred feet, or linear, a few 

 hundred yards in extent. It is locally believed that the underground 

 streams associated with the sinks drain not only the pine land, but help 

 to drain the Everglades to the west, because great springs of constant 

 flow emerge in large numbers along the shore. This is probably true, 

 but the interior drainage perhaps escapes by percolation, or very small 

 channels, for no sinks were seen in or near the Everglades. The pines 

 cover a shore strip about six miles wide between Xew and Miami Rivers, 

 then widening to about fifteen miles in the next twenty-five miles 

 toward the southwest. The southwestern terminus of the pines is not 

 known. 



The Everglades. — A great area of Southern Florida west of the pine 

 belt comprises the Everglades. The cause of the Everglades would seem 

 to be similar to that for the prairies among the pines, — a drainage so 

 defective that much water accumulates during the rainy season, and 

 some even continues through the dry time, though the change in eleva- 

 tion is perhaps two feet. Temporary surface channels to the sea help 

 di'ain the Everglades during the rainy season, but only the larger rivers, 

 as the Miami and New, flow throughout the year. The rivers have a 

 well marked fall line on the limestone, — a few hundred yards of swift 

 water just west of the pines, and representing the progress made by the 

 rivers in cutting back from their mouths. 



At the border of the Everglades the rough surface of the oolite 

 becomes concealed for the most part beneath a mat of grass, and pines 

 grow no farther west (Plate XXIV. Fig. 1). In the zone of oscillation 

 of water the grasses change in character from a small wiry variety near 

 the pines to saw-grass six feet or more tall, and flags and cane growing in 

 water. The Everglades impress one as a sea of grass growing in shal- 

 low water, with countless shallow ponds of clear water in which grow 



