ANNUAL REPORT-MINERAL INDUSTRIES. 35 
No. I. From Gadsden County, Florida. U. S. Geol. Sur. 17tk 
Ann. Rept., pt. Ill (cont.), page 880. 
No. II. From Decatur County, Georgia. Ibid. 
No. III. From Fairburn, S. D. Ibid. 
No. IV. Glacialite, Enid, Okla. G. P. Merrill, Non-mctallic 
Minerals. U. S. Nat. Mus., Rept. for 1899, p. 337, 1901. 
No V. From Sumter, S. C., U. S. Geol. Surv., Min. Reso., 1901, 
p. 933, 1902. 
No. VI. From Alexander, Ark. Branner, Amer. Inst. Min. Eng. 
Trans. XXVII, p. 62, 1898. 
Physical Properties:—The most distinctive physical 
property of fuller’s earth is that already mentioned, 
namely, the property of clarifying oils. When wet the 
fuller’s earth is often of a lean character. This, however, 
is not invariable, as the Gadsden County fuller’s earth 
is sticky when wet. 
Test for Fuller’s Earth:—Fuller’s earth varies in color. 
It may be light buff, or brownish, or olive green or gray. 
It is not readily distinguished in general appearance from 
other clays. When dry fuller’s earth adheres firmly to 
the tongue, but some other clays are also adhesive. A 
practical test of fuller’s earth is necessary in order to 
determine its value. A test may be made by the use of a 
glass tube i to 1 inch in diameter and 2 to 3 
feet long. To make the test support the tube 
in an erect position, the lower end being plugged 
with asbestos fiber. The earth is powdered and 
packed into the tube. Crude oils, vegetable or mineral, 
are then passed through it. If the clay is a fuller’s earth 
the oils will be more or less perfectly clarified, depend¬ 
ing upon the quality of the earth. It has been found that 
a fuller’s earth that will clarify a vegtable oil may not 
affect a mineral oil, while an earth used to clarify a min¬ 
eral oil may be unsatisfactory when applied to a vegetable 
oil. A theory of the action of fuller’s earth in clarifying 
oils is given by Porter as follows (U. S'. Geol. Surv. Bull. 
315. p. 282, 1908) : “Fuller’s earth has for its base a series 
