EXTENT OF EXPLOITATION. 83 



phosphate. A cubic foot of the red rock phosphate weighed about 79 

 pounds ; the gray material weighs from 5 to 8 per cent. more. 



Area and Tonnage of the Phosphate Deposits. 



Careful planiraeter measurements of the phosphate areas, based upon 

 instrumental field work, show the island to have originally contained about 

 244 acres of gray phosphate, confined to the lower flat, while of the upper 

 flat red phosphate there were originally nearly 300 acres. 



Of the gray phosphate area perhaps one-half has been exhausted during 

 the last thirty years of development, yielding about 2,000 tons an acre ; 95 

 acres have been partially worked over and should still yield about 400 tons 

 an acre, while 32 acres is virgin territory, from which the yield may be esti- 

 mated at 1,500 tons an acre. 



The red phosphate areas have scarcely been drawn from at all. An esti- 

 mated area of about 40 acres already worked out is said to have furnished 

 about 45,000 tons, and from this and correlative testimony these upper fields 

 may be expected to yield an average of 1,000 to 1,200 tons per acre. 



The principal deposits on the upper part of the island have been divided 

 into seven large districts or "fields;" but the surveys demonstrate the exist- 

 ence of at least fifty-six additional separate areas, varying from a few square 

 feet up to 165,000 square feet (or four acres) in area, the aggregate of whose 

 yield in tons will be considerable. 



Mining and Transportation Facilities. 



The present methods of digging, transporting and shipping the phosphate 

 material are extremely crude and expensive, and have no doubt been largely 

 the result of plans originally adopted when the material dug occurred close 

 to the present wharf. The company, however, contemplate a radical change 

 in the manner of transporting the phosphate from the diggings to the wharf 

 and vessels, though it is extremely doubtful whether the conditions under 

 which the material exists will justify any change in the system of mining. 

 From the wharf a narrow-gauge railroad track about If miles in length ex- 

 tends along the lower flat to the present diggings, being advanced as the phos- 

 phate is exhausted. Cars 12 feet long and 4 feet wide outside and 9' Ik" X 

 3' 9" X 1' 5'' inside, holding about 50 cubic feet of phosphate, are shoved by 

 hand from the diggings to the wharf, where the material is stored in covered 

 houses. 



The phosphate rock is readily extracted from a series of contiguous pockets, 

 though at a considerable discomfort sometimes to the laborer, who frequently 

 has an opening only large enough to squeeze his body into, affording scarcely 

 room enough to scrape or dig out the material. Occasionally, when the phos- 



XIII— Bull. Geul. Soc. Am., Vol. 2, 1890. 



