32 I'Jic .Imcrican Geologist. J"'y' ^^o^- 
iMabaiiKi material. l'liilli]).s and llancook* conclude, after a 
chemical investigation of the Georgia-i\labama bauxite, based 
on the solubility of the contained alumina in different 
strengths of sulphuric acid, that it consists of a mixture of the 
trihydrate, AL(OH),., with clay, and probably a lower hydrate, 
Al,()....2H.(). The triliydrate is the base or the essential part. 
In the reports issued by the United States Geological Survey 
on the Mineral Resources of the United States, the mineral 
bauxite is referred to as the trihydrate. In his report "On 
the Coosa Valley Region of Alabama," Henry McCalleyf re- 
fers to the Alabama mineral as the trihydrate. After a study 
of hundreds of analyses of the French bauxites LaurJ makes 
the following statement concerning their chemical constitution : 
"\Mien these minerals [bauxites] are studied, not in isolat- 
ed specimens but in mass, it is quickly noticed that there is in 
their composition one constant, so to speak, namely, the gen- 
eral proportion of anhydrous alumina, AUG..,, the average of 
which is about 66 to 69 per cent. This figure is given by the 
analyses of thousands of shipments. Representing this con- 
stant by A. we find three variable elements, e, besides, namely, 
water, silica, and ferric oxide ; and it is a remarkable fact, that 
the sum of the weights of these is constant also at about 27 
per cent. We will represent it by Pe." 
''Finally, the various accessory substances (titanium, van- 
adium, etc.) which occur even in the purest bauxites, present a 
constant total of about 3 to 4 per cent. These we represent 
by C" 
"Thus, the centesimal formula of the bauxites: 68 to 70 
A.\XJ.^+2y {SiOo, FeoO.j, HoO)+4(sundry accessories) may be 
written in general form as A-^Pe+C." 
"But the three variable elements of Pe have the singular 
property of replacing one another, in whole or in part, sepa- 
rately increasing, diminishing, or totally disappearing, without 
change of the total of 27 per cent., and without altering the 
fixed mineral species, which is, according to our view, the bi- 
hydrate of alumina, forming the base of the mineral. These 
varying substitutions give rise to the different types '•' * *" 
*The Commercial Analyses of Bauxite, Jowr. Amer. Clieni. Soc, 1S9S, vol. 
XX, p. 211. 
fGeolog-ical Survey of Alabama, 1897, pp. 79-S-lr. 
|The Bauxites: A Study of a New Mineralogicnl "FamUy, Trans Amer. Inst. 
Min. Engrs., Virginia Beacii Meeting, February, 1894-. (Author's edition, 9 pp ) 
