I 



THE BAUXITE DEPOSITS OF ARKANSAS 277 



Coquand says:' "The aqueous origin of the bauxites is as 

 well marked by their structure as by their stratification and 

 alternation with sandstones, limestones, and clays. It is evi- 

 dent that the sedimentation (at the time the deposits were 

 made) began at the bottom of a lake by the deposition of alu- 

 minous and calcareous matter brought in from mineral sources 

 and to which a certain movement of the waters gave a pisolitic 

 form." It is not altogether clear what M. Coquand means by the 

 "mineral sources" to which he refers several times and to which 

 he attributes the material of the bauxites. His paper ends with 

 the conclusion that the several bauxite localities of France "are 

 of the same age and fall under the head of irregular deposits of 

 geyser origin," from which it must be inferred that he thinks 

 the hot waters of geysers are the "mineral sources" from which 

 the bauxite has been derived. 



M.Stanislas Meunier holds Mhat salt water penetrating to 

 great depths can, on account of its high temperature and the 

 pressure upon it, dissolve the ferruginous shales and form chlo- 

 rides of alumina and perchlorides of iron. When these chlo- 

 rides come to the surface and spread over limestones, as they 

 usually do, a change of bases takes place, alumina and peroxide 

 of iron are precipitated, chloride of lime is carried away and the 

 carbonic acid of the limestone is set free, while the iron and 

 alumina is deposited as bauxite. 



Auge, as stated in the article already referred to, was led to 

 reject Meunier's theory by finding bauxite resting on rocks 

 other than limestones. To this Meunier replies that the chem- 

 ical changes demanded by his theory might be produced by 

 the waters carrying the material passing over limestones and 

 depositing the bauxite further on in their course. 



Daubree says^ that while generally associated with sedimen- 

 tary beds, the bauxite beds show their relations to deep-seated 

 emanations by the presence of anhydrous peroxyde of iron or 



I Bull. Soc. Geol., 2™« sen, 1870-1, XVIII, 98 ff. 

 = Bull. Soc. Geol., s'"^ sen, XVI, 1888, 345-346. 

 3 Bull. Soc. Geol. de France, XXVI, 1868-9, 9i5- 



