The Georgia Bauxite Deposits. — ]Vatson. 41 
formations are intersected by numerous faults, along which 
water has in the past found easy access to great depths. The 
shales are made up largely of silicate of aluminum. Thev also 
contain considerable iron sulphide in the fomi of pyrites. It 
is believed that the surface waters, carrying oxygen in solu- 
tion, gained access to these shales and, by oxydizing the pyrites, 
set free sulphuric acid. This, under the conditions present, 
decomposed the aluminous shales, forming alum and sulphate 
of aluminum. Ascending currents carried these salts in solution to 
the surface, and, coming in contact with the limestone during 
their upward passage, they were decomposed, forming sulphate 
of lime and aluminum hydroxide, together with liasic sulphate 
of aluminum, which was subsequently changed to aluminum hy- 
droxide on exposure to the air. The aluminum hydroxide thus 
produced formed a gelatinous precipitate which collected about 
vents of springs. It was kept in motion by the ascending water 
and thus formed concentric structures. The reactions indicat- 
ed above are all known to take place in nature, and the process 
is one which is readily understood." 
The essential facts which a satisfactory' theorv for the ori- 
gin of the Georgia deposits of bauxite must explain are now 
stated in full. Some of these were stated in connection with 
Dr. Spencer's theory : 
( I ) The bauxite deposits in the Georgia district are most- 
ly confined to the Knox dolomyte. They are not found at anv 
uniform position in the dolomyte but are associated with all 
parts of the formation, giving a wide stratigraphic range. 
( 2 ) The ore occurs in the form of distinct pocket deposits 
of varying sizes and disconnected, with the vertical nearly 
equal to the horizontal dimension. 
( 3 ) The absence of foreign material, such as might be 
derived from the inclosing rocks in the ore-bodies and their 
associated l)auxitic clays and kaolins. The pronounced dif- 
ference in the bauxitic clays and the inclosing residual siliceous 
clays with no indication of commingling with or gradation into 
each other. 
( 4 ) The location of the deposits with reference to alti- 
tude and topography. Some of the ore-bodies occur below the 
850-foot level, and a few are found above 950 feet ; but where 
