124 CLASSIFICATION OF THE PtTBOC LANDS. 



phosphoric acid contained in 60 pounds of high-grade phosphate 

 rock. At this rate 12,000,000 tons of high-grade phosphate rock, ap- 

 proximately four times the production in l&ll, or one-third the total 

 marketed production in the United States from 1867 to 1911, would 

 be required each year simply to offset the depletion of the -100,000,000 

 acres of cultivated land in the United States, the question of increas- 

 ing the present agricultural yield not being considered. 



Phosphate or rock phosphate is a mineral substance made up of 

 lime and phosphoric acid and is the principal source of the phosphate 

 of commerce. Its value is becoming more apparent and more clearly 

 recognized in the United States, not only through the decreasing 

 yield per acre of cultivated lands but also through the discovery of 

 the fact that some virgin lands are deficient in this essential to plant 

 growth. The marketed production of phosphate rock in the United 

 States increased from 448,567 long tons in 1888 to 11,900,693 long 

 tons in 1911. The rock phosphate is used as raw rock flour (or 

 " floats ") or in the form of a superphosphate, which is made by 

 treating the rock with sulphuric acid. 



LANDS CONTAINING PHOSPHATE. 



The commercially available phosphate deposits of the pubiic do- 

 main are those in Florida and those of the western fields, which, so 

 far as investigated at present, are confined to the States of Idaho, 

 Montana, Wyoming, and Utah. 



Deposits of phosphate in the Rocky Mountain States were first 

 discovered in northeastern Utah and southeastern Idaho, in the 

 vicinity of the Idaho-Utah-Wyoming line-. From this locality 

 the deposits have been traced south, east, and west halfway across 

 the States of Idaho, Utah, and Wyoming and northward to the vicin- 

 ity of Helena, in west-central Montana, so that the phosphate beds 

 now known cover an area extending about 220 miles from east 

 to west and 420 miles from north to south. Of course only a small 

 part of this territory is underlain by deposits that are commercially 

 valuable. 



Deposits of phosphate rock exist also in Tennessee, South Carolina, 

 and Arkansas, but these deposits are on lands that have passed into 

 priv.ate ownership. The production of Tennessee is increasing, that 

 of Florida appears to have about reached its maximum, the South 

 Carolina output is diminishing, and the Arkansas deposits are of 

 low grade. For these reasons the largest future production must 

 come from the western fields, where the deposits are chiefly on the 

 public lands, although Florida will remain an important factor in 

 production for many years ^o come. 



