16 



lies many square miles of surface continuously, at a depth 

 ranging from six inches to twelve or more feet, and in such 

 quantities, that from live hundred to a thousand tons underlie 

 each acre. In fact, it seems there are no rocks in this section 

 which are not phosphates. 



"The area of this bed, containing phosphates of good quality 

 and in workable quantity, so far as known and examined by 

 the writer in person, is not less than forty to fifty square miles, 

 though from samples I have examined from beyond these 

 limits, I am led to believe that the rock will be found of good 

 or indifferent quality, and in greater or less quantity, over an 

 area of several hundred square miles. When of inferior quality, 

 they contain more sand, carbonate of lime, oxide of iron, and 

 phosphate of iron and alumina, and proportionately less pure 

 phosphate of lime." 



As the amount of this material is so large, it will doubtless 

 be the chief source of supply for many years to come, and there 

 will probably be little variation in its pice; and as there are no 

 drawbacks or checks to the mining and economical transporta- 

 tion of it to all parts of the Atlantic coast, we will estimate 

 the value of insoluble phosphoric acid from it. We give th& 

 following tables from Dr. Pratt's interesting pamphlet on the 

 " History of the Discovery and Development of the Native 

 Bone Phosphates of the Charleston Basin," giving analyses of 

 different samples of this guano, and of some other leading com- 

 mercial guanos, for comparison. 



