REVIEWS 823 



geneous character of the formation is explained by the caving in of solu- 

 tion cavities and their subsequent refilling. 



The theory presented seems to explain the larger features of the 

 phosphate deposits, but the report should be considered a statement of 

 progress of investigation, rather than the last word in explanation of 

 the deposit. 



W. B. W. 



Water Supply of Eastern and Southern Florida. By E. H. Sellards. 

 Florida Geol. Survey, Fifth Annual Report, 1913, pp. 113- 

 288, pis. 5, figs. 17, map 1. 



This report covers in detail an area of twenty-two counties in which, 

 for the most part, the artesian waters may be tapped by flowing wells. 

 This area includes the outer rim of counties along the eastern, southern, 

 and southwestern borders of the state. 



The principal aquifer is the Vicksburg limestone of Oligocene age. 

 Underlying the whole state, this formation is exposed in the central part 

 and dips beneath younger formations to the east and south. These 

 younger beds have not been well differentiated and some wells may 

 obtain water from them, but strong flows are from the Vicksburg. 

 The structure includes a low anticline with its axis dipping gently to 

 the east in the central part of the state. The water-bearing horizon is 

 100 feet below the surface along the coast, and near the crest of the anti- 

 cline. In the northeast corner of the state the wells are from 300-400 

 feet deep and at the southern extremity from 900-1,000. 



The gentle dip of the strata does not furnish strong pressure in any 

 locality and a head of 25 feet is rather exceptional. Local topography 

 affects the distribution of the flowing wells. 



In some areas there has been great development of the artesian water 

 supply. There are not less than 500 flowing wells in the city of Jackson- 

 ville. Statistics covering recent years show a progressive loss of flow 

 from the wells in this city. 



Much of the artesian water of the state is not potable on account of 

 mineral salts, chiefly sodium chloride. This is notably true in the 

 southern part. All the underground water of the state is very generally 

 charged with hydrogen sulphide, but its use for domestic purposes is 

 not prevented thereby. 



A small area of flowing wells in the western part of the state is not 



treated in detail in this report. 



W. B. W. 



