22 proceedings: geological society 



taming dissolved cupric sulphide, appear as intermediate products. 

 The logical conclusion from the data is that secondary chalcopyrite, 

 bornite, and covellite are earlier stages of a process which was inter- 

 rupted before it was complete. Many reactions, such as the synthesis 

 of bornite and chalcopyrite in the wet way, have been worked out. 



Discussion: G. F. Loughlin inquired regarding rate of oxidation of 

 galena in comparison with sphalerite. Allen replied that with galena 

 the action is rapid at first but an insoluble coating soon forms and 

 action ceases. E. S. Bastin spoke of a phenomenon he had observed 

 in field work. In a certain type of enrichment covellite, chalcocite, 

 etc. form; in another type only chalcopyrite. In the latter case galena, 

 sphalerite and carbonates are prominent accompanying minerals. He 

 asked Allen if he had any explanation. Allen replied that his experi- 

 ments did not offer any suggestion. He emphasized the fact that the 

 end product of true equilibrium between sulphide ores and copper sul- 

 phate solutions is not chalcopyrite but chalcocite. A. C. Spencer 

 asked if it were possible that in processes of secondary enrichment mi- 

 gration of copper in carbonate solutions had taken . place. Allen 

 thought that an obstacle to such a conception was the lack of the 

 necessary oxidizing agent. 



C. Wythe Cooke: The age of the Ocala limestone of Florida. The 

 Ocala limestone, which has heretofore been thought to represent the 

 concluding stage of the lower Oligocene (Vicksburg group) and to overlie 

 the Marianna and "Peninsular" limestones, occurs at Marianna, 

 Florida, lying unmistakably beneath the Marianna limestone, which is 

 of Vicksburg age. Critical study of the list of fossils from Ocala pub- 

 lished by Dall in 1903 shows that the formation is of upper Jackson 

 (Eocene) age. The "Peninsular" limestone is in large part identical 

 with the Ocala but may include other formations. 



Discussion: R. S. Bassler spoke of the great difficulties encountered 

 in working out stratigraphic relations in the Southern States, due 

 principally to lack of satisfactory outcrops. T. Wayland Vaugran 

 referred to some of the structural relations which had led former workers 

 astray. One of the chief factors was the presence of an erosion un- 

 conformity and the lack of certain members in certain type sections. 

 L. W. Stephenson thought that one of the chief points brought out 

 by the paper was the necessity for very careful paleontologic work. 



C. N. Fenner, Secretary. 



The 299th meeting was held in the lecture room of the Cosmos Club 

 on November 10, 1915. 



informal communications 



W. T. Schaller described briefly a kaolinite from Oklahoma which 

 was of very pure composition, but remarkable for intumescence before 

 the blowpipe. 



