140 FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT

weekly to New Orleans from Pensacola. He also states that fire-brick in particular were in great demand and brought a very good price. The same author, writing in 18371, reiterated the same conditions.
 Crary2 made both mud and dry-press brick on Escambia Bay from 1856 to 1860 for the construction of Fort Jefferson on Dry Tortugas Island. He later established a brick plant at Bluff Springs in the northern part of Escambia County. The same author,;' in writing of fire-clays, says "the best developed beds of fire-clay are found in Escambia County, Florida. In fact, the whole county is underlain with one vast indeterminable bed of potter's clay and fire-clay, in strata from six to forty feet deep, often cropping out on the surface. This clay is suitable for all kinds of pottery, for fire-brick, and for the very best kinds of building brick, or blocks for paving, and is cheap, accessible and in every way advantageously situated for profitable manufacturing." Crary, however, defines fire-clay as "antediluvial or primitive clay".4 The term "primitive clay" is here applied to bedded deposits of clay which were not of floodplain origin. This definition of a fire-clay is not now accepted and the clays of Escambia County referred to by Crary are not fire-clays.
 The Citronelle formation underlies much of Escambia County and in most places is overlain unconformably by more recent sediments. Both the Citronelle formation and the undifferentiated Pleistocene sediments above consist essentially of lenticular, cross-bedded and interstratified sands and clays. Clays, however, form the greater part of the Citronelle section while sands prevail in the Pleistocene deposits.
 An erosional unconformity separates the Citronelle formation from the Pleistocene. Other minor unconformities may be observed in numerous places. In a sand-clay pit about five miles north of Pensacola on the Flomaton road an unconformity occurs between two clays and is marked by a half-inch layer of limonite.
 Layers of limonite, in places as much as six inches in thickness, are of conmon occurrence in several of the clay exposures where they mark the contact between two clays or between a sand and a clay. These limonitic layers probably represent zones of concentration formed from descending waters which have leached out the iron from the overlying

 lWilliams, John L., Territory of Florida, p. 114,.1837.
 2Crary, J. W., Sr., Brickmaking and Burning, pp. 14 and 35, 1890.
 3Same, p. 3.
 4Same, p. 28.