278 J. C. BRANNER 



oligiste, which generally colors them, and by its ramifications 

 generally penetrating underlying beds and by the juxtaposition 

 to granite. 



R. G. Symes thinks that the bauxite at Estertown, County 

 Antrim, Ireland,^ "seems to be a mud lava." 



The most exhaustive study yet made of bauxite is that of 

 Dr. A. Liebrich, the title of whose treatise is given in the bib- 

 liography at the end of this paper. He quotes Streng as hold- 

 ing that the Vogelsberg bauxite is derived from basalt by 

 decomposition, and, in general terms, Liebrich endorses this 

 view. Further on, however, he states that it is "not the 

 decomposition product of an underlying basalt, but of a com- 

 pletely disintegrated anamesite lying above a compact basalt." 

 Again he savs : "There is nowhere bauxite containing a kernel 

 of stone which is not a decomposition product." Again "the 

 transition between bauxite and basaltic hematite may be traced 

 step by step in thin sections." Also; "it is to be regarded as 

 a concretionary formation which has originated in the clay 

 formed by decomposition of rock, and that it is therefore not a 

 simple process but several different processes following each 

 other." He thinks, however, that other kinds of basalt than 

 anamesite can yield bauxite. He also concludes from his micro- 

 scopic and chemical studies of bauxite that it is the same as 

 hydrargillite. The chemical process and the method of form- 

 ing the pisolites, he says, is unknown. 



Of the theories above mentioned the only one that appears 

 to be applicable to the Arkansas deposits is that of hot waters. 

 This however is not necessarily in conflict with the theory of 

 Liebrich that they are decomposition products, though they are 

 not, in the present case, associated with basalts, and are cer- 

 tainly not formed by the decomposition of any rock in place. It 

 is my opinion that before the eruptive syenites had cooled they 

 were sunk beneath the Tertiary sea, and that either by the con- 

 tact of the sea water or by the issuing of springs whose waters 



' Memoirs of the Geological Survey of Ireland, Mem. accompanying Sheet 20, 

 p. 12. 



