RECORDS OF MEETINGS 287 



The first item of the progTamme of the evening Avas the discussion of 

 Mr. Earle's paper on the "(ieiiesis of Certain Paleozoic Interbedded Iron 

 Ores/' which was presented at the April meeting of the Section. 



Professor Kemp opened the discussion by inquiring : 



(1) Are there not other oolites than the Clinton which have been 

 replaced ? 



(2) Would there not be stagnation of water below the vadose region? 

 Mr. Eakle referred the first question to his colleagues and replied to 



the second by stating that the imper^dous strata are not wholly so, but 

 only more so than their contained, loosely aggregated beds. Moreover, 

 he believes, there has been a fluctuation of the ground water level. He 

 thinks also, in reply to Professor Stevenson's inquiry, that the fragments 

 in the superjacent beds are not directly in contact with the iron-forma- 

 tion and cited replacement of pebbles and not of their matrix, as also 

 described in U. S. Geological Survey Bulletin No. 430. 



Professor Grabau then discussed the iron deposits in Tennessee, stating 

 that they are replaced fossils which have not been rolled. He observed 

 that the deposits in Wisconsin have pebbles with surfaces resembling 

 desert varnish and that the pebbles lie at all altitudes. There are no 

 fossils. The beds are lens-shaped. There is apparently wind cross-bed- 

 ding. There is little cementing silica. He believes that limestone in 

 these instances has been replaced by the iron. 



Professor Woodmax, in describing the iron ores of Xova Scotia, showed 

 that various materials are replaced and that there are isolated granules 

 of iron ore contained in a matrix of mud. He maintains that the cav- 

 ernous consolidations are unexplained by the syngenetic tlieory ; also that 

 there is either partial replacement or partial leaching in various regions. 

 He finds that the typical examples of replacement are by siliceous and 

 not calcareous materials. 



Dr. A. B. Pacini followed with observations on the chemistry of the 

 deposition of iron, showing that as yet too little is known concerning such 

 processes in nature to prophesy certainly as to oxidizing or deoxidizing 

 conditions underground. He referred to Van Bemmelen^s ■ results, which 

 show that the yellow oxides of iron deposited chemically are non-colloidal, 

 while the red are colloidal. 



Dr. Pacini then gave account of laboratory experiments in passing iron 

 in solution in carbon dioxide through porous calcite and silica at 10 

 atmospheres pressure. He secures some replacement in a few hours. 

 The experiments are still under Avay. 



