154 ANNALS NEW YORK ACADEMY OF SCIENCES 



yet depend upon a condition of ore deposition unknown at any other 

 time, the direct precipitation of iron ores in sea-water. Posepny says 

 (273, p. 131) 



"In short, a number of investigators have adopted the hypothesis of an 

 original deposition from the ocean without giving any other reason than the 

 observed relations of stratification. Yet, in a considerable experience with 

 ore-deposits in marine limestones, I have never, been able to find genuine ore- 

 beds among them, but always only ores of subsequent introduction ; so that I 

 feel warranted in believing that such beds proper do not exist." 



They recognize many factors that are difficult to explain under tlieir 

 hypothesis. Many conditions are found that cannot be accounted for 

 under this theory. Moreover, the principal points, in favor of the sedi- 

 mentary theory apply equally well to the Artesian Replacement Theory. 

 The field conditions, hard to account for under the sedimentary hy- 

 pothesis, are expectable under the latter theory. Instead of relying upon 

 ■conditions unkno'WTi before or since, the writer bases his deductions only 

 Tipon well recognized conditions that are known to have been in operation 

 ■during many geological periods. 



The writer has therefore come to the following conclusions in regard 

 "to the origin of most of the Paleozoic interbedded iron-ore deposits : 



1) The Clinton strata were favorable for the deep penetration of sur- 

 face water along well defined runways of porous rock, protected top and 

 bottom by impervious strata. 



2) Iron-bearing solutions actually did penetrate these artesian slopes 

 and were to a large extent responsible for the deposition of the Clinton 

 hematites and other interbedded iron-ore deposits. 



3) The strata were evidently marine but chiefly of a near-shore t\^e, 

 as shown by shallow-water conditions such as the accumulation of large 

 deposits of fossil fragments, evidently broken to pieces by the action of 

 shore waves and ocean currents. 



4) Corals were found in sufficient number to indicate that conditions 

 necessary for successful growth of the polyp, such as mild climate, shallow 

 water, open sea and a lack of much fresh Avater, must have existed. 



As the beds were marine, shore or near shore deposits, they must have 

 been formed with a gentle seaward dip. 



The Silurian Sea producorl all of tlio conrlitions necessary for artesian 

 slopes. 



After these strata were formed, elevation took place, so that the out- 

 crops were above the sea and the porous layers were then in a position to 

 receive surface water. Then came a period, or possibly several periods, 

 of considerable precipitation and abundant weathering; large volumes of 



