134 Papers from the Marine Biological Laboratory at Tortugas. 



carbonic-acid gas from passing over large areas of decaying vegetable 

 matter; and, as the flow toward the sea is gentle, there is opportunity 

 for the dissolving acid to act on the limestone. Over a considerable 

 area in the Everglades, although limestone underlies the surface material, 

 the water is prevented from coming in contact with it. Therefore, most 

 of the solution must be accomplished on the higher region of the Miami 

 oolite and the coastal fringe of the Lostman River limestone. There is 

 also chemical denudation on the Key Largo limestone and Key West 

 oolite of the keys. The following quotation from Dr. Sellards is appro- 

 priate in this connection: 



Among these agencies of erosion, underground water has acted in Florida 

 under exceptionally favorable conditions. In areas of considerable slope, and 

 with relatively impervious formations, the surface run-off is large. Under these 

 conditions those features of topography determined by the rapid downward cut- 

 ting of the surface streams and their tributaries predominate. In Florida the sur- 

 face slope is slight. The open nature of the soil and rock permits the greater part 

 of the water to enter the earth, establishing subterranean rather than surface 

 drainage. The rocks are prevaihngly calcareous and soluble. Under these con- 

 ditions the work of the underground water predominates over surface erosion. In 

 central Florida the topography, soil, and general surface features are determined 

 to a large extent by the work of underground water. 



Solution is the most apparent, and geologically the most important result 

 of underground water circulation. Rainwater, while passing through the air, 

 takes into solution a small amount of CO, gas. To this is added organic and mineral 

 acids taken up while passing through the soil. Increased pressiu-e, as the water 

 descends into the earth, enables the water to hold in solution greater quantities 

 of gases, acids, and salts, all of which greatly increase the dissolving power of the 

 water. 



That underground water is efficient as a solvent is evident from the analyses 

 of well and spring waters. Rainwater entering the earth with almost no solids in 

 solution returns to the surface through springs and wells with a load of mineral 

 solids in solution determined by the length of time it has been in the ground, the 

 distance traveled, and the character of the rocks and minerals with which it comes 

 in contact. 



The mineral matter thus taken into solution is carried along with water, and 

 while some of it is redeposited, a large amount is removed annually. An estimate 

 of the total mineral solids thus removed is difficult. A conception of the largeness 

 of the amount removed is obtained from a consideration of some of the individual 

 springs. 



The water of Silver Springs contains, as shown by analysis, 274 parts solids 

 per 1,000,000 parts water. Otherwise expressed, each 1,000,000 pounds of water 

 is carrying with it 274 pounds of solids in solution. Silver Spring is estimated to 

 flow a little more than 3,000,000 pounds of water per minute (368,913 gallons). 

 The interior of Florida is thus being carried into the ocean through Silver Springs 

 at the rate of more than 340 pounds per minute or about 600 tons per day. 



The total solids removed in solution through 6 other springs of central Florida, 

 expressed in tabular form, gives the following results: 



' Organic matter is deducted from the total solids as given for Suwanee Sulphur and White Sulphur 

 Springs. The organic matter occurring in the other springs is of small amounts and was not separately 

 determined. 



