THE PHOSPHATE NODULES. 53 



The land along up the Ashley is rolling, with low bluffs 

 coming down to the river and lying at right angles to it, rising 

 perhaps from twenty to forty feet high. Between these bluffs 

 lie swamps, through many of which canals have been dug, 

 originally for the purpose of drainage and the culture of 

 cotton. On these low lands the top soil, generally rich, is 

 from four to six inches deep, below which comes a layer of 

 sand from six inches to a foot and a half in depth, and below 

 this sand comes the layer of phosphate nodules, packed quite 

 closely together and imbedded in more or less clay and mud, 

 which holds them so firmly that they are picked out with the 

 common pick. These nodular rocks vary in size from that 

 of a hen's egg to that of a man's head. They are very irreg- 

 ular in shape, rounded, water-worn, cavernous, as if bored 

 by the teredo or other marine mollusks. They are hard, 

 compact, rock-like, often brown in color, and heavy, though 

 the consistency and weight differ greatly, some specimens 

 being much softer and lighter than others. (Many specimens 

 were here shown to give an idea of the shapes, the size and 

 character of the nodules.) If a specimen is broken, and the 

 two surfaces are rubbed together, a strong organic odor is very 

 perceptible, and this is so characteristic as to be a common 

 mode of detecting the phosphates throughout this region, both 

 in the hard and the soft varieties and in dry and wet speci- 

 mens. 



On the bluffs the layer of sand lying just beneath the thin 

 surface-soil is generally thicker or deeper than in the hollows 

 or lower lands, and the stratum of phosphate rocks lies conse- 

 quently deeper. The phosphate layer varies in thickness from 

 six inches to a foot and a half or two feet, sometimes to three 

 feet, though this is greater than the average. Where the 

 strata average fifteen to eighteen inches in thickness the quan- 

 tity yielded per acre is very large, in some cases thirteen 

 hundred tons or more, to say nothing of the large amount 

 wasted, the smaller lumps being entirely neglected. Six 

 hundred to a thousand tons per acre is not an uncommon 

 yield. 



It has been estimated, taking the extent of the deposit 

 where it is already known to exist and the general average 

 yield per acre, that there must be not less than sixteen hun- 



