The Phosphates of America. 69 



1. A foundation of upper eocene limestone rocks very much 

 cracked up and fissured, the cracks having a general trend north- 

 east and southwest. 



2. Irregular beds, pockets or banks of miocene deposits, dried 

 and hardened by exposure, and alternately calcareous, sandy or 

 marly ; generally phosphatic, and sometimes entirely made up of 

 decomposed organic debris, the phosphoric acid being combined 

 with various bases (lime, magnesia, iron, alumina, etc.). 



After the disappearance of the miocene sea there came some 

 gigantic disturbances of the strata. There were upheavals and de- 

 pressions. The underlying limestones were probably again split 

 up, and the miocene deposit was broken and hurled from the sur- 

 face into yawning gaps and from one fissure to another. 



Now came the pliocene periods, or end of the tertiary, and then 

 the seas of quaternary age, with their deposits and drifts of shells, 

 sands, clays, marls, bowlders and other transported materials, and 

 the accompanying alternate or concurrent influences of cold, heat 

 and pressure. 



If we take the whole of these phenomena broadly into consider- 

 ation, we must be led to conclude that those portions of the phos- 

 phatic miocene crust which did not fall into permanent limestone 

 fissures or caverns at the time of the disturbance of the strata, be- 

 came at length very thoroughly broken up and disintegrated. They 

 were rolled about and intermixed with sand, clay and marls, and 

 were deposited with them in various mounds or depressions in con- 

 formity with the violence of the waters, or with the uneven struct- 

 ure of the surface to which they were transported. 



Occasionally this drifting mass found its way into very low- 

 lying portions of the country, say into those regions where consider- 

 able depression was brought about by the sinking and settling of 

 the recently disturbed mass. At other times it was rolled to and 

 deposited on slightly higher points. In the first of these cases we 

 find a vast and complete agglomeration, comparable to an immense 

 pocket, of broken-up phosphate rock, finely divided phosphate debris, 

 sands, clays and marls, all heterogeneously mixed in together. In 

 the second case we find the phosphate in large bowlders, sometimes 

 weighing several tons, and intermixed with but relatively small 

 proportions of any foreign substances. 



Considering these phenomena, we reach the conclusion that the 

 features in the Florida deposits of phosphate to be most particu- 

 larly emphasized, are that the formation consists essentially of 



