pen-Kobe.] PHOSPHATES OF SOUTH CAROLINA. 67 
includes not only the deposits in these rivers, but also the deposits in 
the Coosaw and Beaufort Eivers and those on Chisholm's Island. This 
area is essentially a river mining district, though phosphate of good 
quality is mined on parts of Chisholm's Island by- the Pacific Guano 
Company and by Messrs. Wiley and Gordon. Nodules of excellent 
quality are obtained from the bottoms of the Bull and Coosaw Eivers, 
but those of Beaufort Biver are generally very siliceous, the separate 
grains of sand being plainly visible to the naked eye. 
Outside of the localities mentioned above, phosphatic nodules have 
also been obtained from the upper part of Hospa Creek and from the 
Coosawhatchie Biver (see map, PI. I). Besides the bed of phosphatic 
nodules already described, other beds have been found in boring arte- 
sian wells in Charleston and the neighborhood which are at a much 
greater depth and are of a similar nature. Dr. C. U. Shepard, jr., in 
speaking of these borings, says : 
The samples thus collected Lave been carefully examined and analyzed, the most 
important contribution to our knowledge being the discovery of the existence of sev- 
eral deeper layers of phosphate rock, occurring at the depth of 300 feet from the sur- 
face, and, in the form of isolated pebbles, to a much greater distance. These lower 
deposits are probably not thicker than a few inches, and consequently they lack all 
but scientific interest. 
The phosphate of South Carolina is obtained from the land and from 
the river bottoms. The mining on the land is done in open trenches. 
The area to be mined has to be ditched in order to drain it before min- 
ing operations can be begun. Sometimes it is necessary to build em- 
bankments, to prevent the diggings from being flooded in stormy 
weather. At the Bolton mine, on Stono Biver, high tides sometimes rise 
two feet above the level of the land. Drainage is, in some mines, hast- 
ened by the use of steam pumps. It does not usually pay, unless the 
phosphate is of extraordinary quality, to remove more than eight or nine 
feet of overlying earth. The Pacific Guano Company, however, has 
lately introduced the use of a steam excavator to dig the nodules, and 
it is supposed that work can be profitably carried on at a greater depth 
with this machine than with pick and shovel. 
The phosphate is carried on cars, generally drawn by an engine, from 
the mines to the washers. Here it is broken by machinery into coarse 
fragments not larger than about five inches in diameter, and then passed 
into the washers, where it is freed from the adhering sand and clay. 
Several different kinds of washers are used. The most common one is 
a long trough, in which revolves a shaft armed with a projection in the 
form of a broken helix. The trough is inclined at a small angle. The 
nodules are passed from the breakers to the lower end of the trough 
and are forced up the inclined plane by the revolving shaft against a 
strong stream of water. Sometimes the phosphate is washed in a re- 
volving cylinder perforated with holes and supplied on the inside with 
spiral flanges of steel. A stream of water is thrown into the cylinder 
(541) 
