MUSEUM OF COMPARATIVE ZOOLOGY. 151 



tions, but basins of water of such profundity that they have not become 

 closed by the swamp-building forces. The section of the lake district 

 extends from near Waldo to Lake Kissimmee, or perhaps yet farther 

 south. It has a length of at least two hundred miles and a width of 

 about eighty miles, though its limits in each direction are obscure ; the 

 area of open water basins gradually shades olf into the area of the 

 shallower depressions, now entirely occupied by swamps. By my rather 

 untrustworthy barometric observations, the highest point of the surface 

 in this lake district in the region about Apopka rises to near three hun- 

 dred feet above the sea. The number of basins contained in the area is 

 very great. If all those containing permanent open water were enumer- 

 ated, the total would probably amount to several thousand. In size 

 they vary, from the larger bodies, such as Lake Apopka, with a diameter 

 of ten miles or more, down to basins a few score feet across. 



The most interesting feature in this district is the increase in the 

 measure of irregularity in the hills, as we rise above the sea level. On 

 either side, in passing from the shore, we cross a region which, though 

 occupied by sands, has, as before noted, a gently rolling aspect, remind- 

 ing one of the undulations of the sea when the waves of a great storm 

 have nearly sunk to rest. This is the condition of surface for a height 

 of from ten to thirty feet above the shore. For each fifty feet of as- 

 cent, careful observation shows a decided increase in the amount of the 

 irregularities, until they attain their maximum relief in the uppermost 

 portion of the country. So far as I have been able to ascertain, sub- 

 stantially all of these irregularities are moulded in recent sands. Only 

 occasionally are they affected by the form of the surface which existed 

 before the drifting sands came to this region. In certain cases the 

 underlying rocks are of a calcareous nature, and have been eroded by 

 subterranean waters. Where this has occurred, the pits formed in the 

 sands have occasional sink-holes in their bottoms. Some scores of such 

 openings w-ere seen in the course of four days' journeying between 

 Seville and Lakeland, in Polk County. It seems to me, however, that 

 these pits are not in any measure due to the causes which produced the 

 sink-holes. The great variety in their size, the lack of order in their 

 disposition on the surface, as well as the chance sections aflForded by 

 railways, all indicate that 'lie sink-holes are occasional concomitants of 

 these depressions, and in no sense their cause. My observations show, 

 moreover, that the sink-hole openings are often in eccentric positions in 

 relation to the pits, in some cases being actually above the lowest point 

 of the depression. 



