338 REPOET OF NATIONAL MUSEUM, 1899. 



This material when placed in water falls away to a loose flocculent pow- 

 der, which shows up under the microscope in the form of sharply angu- 

 lar colorless particles, very faintly doubly refracting, without crystal 

 outlines or other physical properties, such as will determine their exact 

 mineral nature. The particles are of all sizes, from the larger floccu- 

 lent masses, some 0.25 mm. in greatest diameter, down to those too small 

 for measurement. The greater number lie between 0.005 and 0.01 

 mm., though a very large proportion are even smaller, not exceeding 

 0.002 mm. These smaller particles are angular in outline and almost 

 perfectly colorless. Their appearance under the microscope is some- 

 what that of decomposed cherts. 



In addition to the faintly doubly refracting particles above men- 

 tioned, there are occasional clear, colorless, sharply angular particles 

 of a doubly refracting mineral which can only be referred to quartz. 

 A few yellowish iron-stained particles are suggestive of residual prod- 

 ucts from decomposition of iron magnesian silicates. 



The Gadsden County, Florida, fullers' earth (Specimens Nos, 53254 

 and 53255, U.S.N.M.) is a light-gray material, often blackened by 

 organic matter, and which shows under the microscope the same 

 greenish, faintl}^ doubly refracting particles as does the English, inter- 

 mixed with numerous angular particles of quartz. This earth its quite 

 plastic and sticky when wet. A section of the beds at the pits of the 

 Cheesebrough Manufacturing Company, as given in The Mineral 

 Resources for 1895-96, is as follows: 



Soil inches.. 18 



Red clay feet 3 



Blue clay do 3 



Fullers' earth do 5J 



Sandy blue earth do 3 



Fullers' earth (second bed) 



