^s•^-^ 



SECTION OF FIELD COVERED WITH PILES OE CANAL MUD RECENTLY APPLIED AT THE 

 RATE OE MORE THyVN yo TONS PER ACRE 



Taken out of the canal up the three flights of earth steps shown in the lower part of the 



figure 



a generation has swept into the sea soil 

 fertility which only centuries of life could 

 accumulate, and yet this fertility is the 

 substratiun of all that is living. 



RIVERS OE PHOSPHORUS 



The rivers of North America are esti- 

 mated to carry to the sea more than 500 



tons of phosphorus with each cubic mile 

 of water. To such loss modern civiliza- 

 tion is adding that of hydraulic sewage 

 disposal, through which the waste of 500 

 millions of people might be more than 

 194,300 tons of phosphorus annually, 

 which could not be replaced by 1,295,000 

 tons of rock phosphate 75 per cent pure. 



949 



