222 FLORIDA GEOLOGICAL SURVEY-15TH ANNUAL REPORT

 Moreover the present deposits of this material probably represent remnants of a formerly continuous deposit covering, at least, a large portion of central-peninsular Florida. The presence of quartz and mica indicates that the material was derived from the residual clays of some granitic region, probably upper Georgia. That the ultimate source of the material was to the northward is indicated by the fact that the larger pebbles are found in the northern part of the region as is pointed out by Ries.1
 Davis2 in attempting to explain the high plasticity of these clays says that they are probably flood-plain clays and are supposed to have resulted from the transportation and deposition of material from a granite area. In continuing this same line of thought, Watkins3 says: "It is very probable, however, that this kaolin was first deposited in Cretaceous times and later eroded and transported to its present position. As this portion of Florida is several hundred miles farther from the crystalline area than the Cretaceous horizon, it is reasonable to suppose that the particles of kaolin held in suspension for so great a distance would be more finely divided than those which were deposited in Cretaceous beds. This, to some degree, may account for the fact that the Florida clays are more plastic than the Cretaceous clays."
 A different theory was earlier suggested by Sellards4 when he said: "The admixture of finely divided clay, kaolinitic in nature, with the coarse sands which characterize these deposits, is difficult to account for, except upon the hypothesis that when deposited the formation consisted of coarse quartz and feldspar sands. The quartz being more resistant has remained but little changed, forming the coarse sand of the formation. The feldspar sands, since their deposition, have been subjected to decay, thus forming the kaolinitic clay of the present formation."
 This -theory encounters serious objections. If climatic and physiographic conditions similar to those of the present are postulated

 1Ries, H., The Clays of the United States East of the Mississippi River, U. S. Geol. Survey Prof. Paper No. 11, p. 82, 1903.
 2Davis, N. I The Plasticity of Clay and Its Relation to Mode of Origin. Trans. A. I. M. E., Vol. 51, pp. 451-480, 1916.
 3Watkins, Joel H., White-Burning Clays of the Southern Appalachial States, Trans. A. I. M. E., Vol. 51, pp. 481-501, 1916.
 4Sellards, E. H., The Soils of Florida, Florida Geol. Survey, Fourth Annual Report, p. 21, 1911.