THE BAUXITE DEPOSITS OF ARKANSAS 275 



by which the deposits have been made, for it is only in this 

 way that we can anticipate the peculiarities of its distribution. 

 There is therefore given below, as briefly as possible, the several 

 theories that have been advanced to explain the method by 

 which bauxite deposits have been made. 



The Arkansas beds appear to have been laid down in water 

 near the shore, but the material does not seem to have been car- 



Fig. 4. Ideal Section through Fourche Cove. 



ried far from the spot at which it originated, or to have been 

 widely distributed by the water. They are all at or near the 

 contact between the palaeozoic sediments and the eruptive sye- 

 nites. Several of them, however, have no palaeozoic rocks 

 exposed near at hand, and one of them has no syenite expo- 

 sures. These conditions are shown in part by the following 

 ideal section illustrating the relations of the rocks about the 

 Fourche Cove. 



The concretionary structure of the bauxite suggests that it 

 has been formed in some such manner as the oolites or sprudel- 

 steins of the well-known hot springs at Carlsbad. At this last 

 named place the oolites are made of carbonate of lime. The 

 water is charged with lime, and as it issues the lime collects 

 about centers. These masses are kept in motion in the rising 

 waters until by accretion they become so heavy that they sink 

 to the bottom. 



Oolites are also made in various other ways, such as the roll- 

 ing of grains upon a shore and in waters heavily charged with 

 lime, by lime secretions of certain algae ^ and other organisms," and 

 possibly by insect eggs as suggested by M. Virlet d'Aoust.3 



'On the formation of oolite. By Dr. A. Rothpletz. Amer. Geol. X, 279-282. 

 ='The formation of oolite. By E. B. Wethered. Quar. Jour. Geol. Soc, LI, 

 1895, 196-209. 



3 The Geologist (I), 1858, 72-73- 



