152 ANNALS NKW YORK ACADEMY OP SCIENCES 



I'urtlier tend to strengthen the artesian theory that such variations in 

 mineral content exist. 



VARIATIONS I\ TEXTURE 



Variations in texture wouhl l)i' inevitable, exactly as they occur to-day 

 in any series of marine shore deposits, ajid the texture of the different 

 ore seams varies as would he expected, seams of fine ore and seams of 

 coarse in the same localities being found, and also variations within the 

 same seams. 



VAUIA'nON.S IN RICHNESS 



Artesian conditions would also account to a large extent for the varia- 

 tions in richness of the Clinton ores of different localities and for varia- 

 tions within the same seam. Differences in temperature, pressure, rate 

 of flow and size, shape and composition of the grains of sand within the 

 porous layers would all influence the degree of richness of the ore, as 

 would variations in the nature of the cement. 



Artesian replacement, therefore, would account satisfactorily for de])th, 

 extent along the dip and wide distribution of the ore deposits. It would 

 apply equally well to the fossil ores or to the oolitic hematites, aiul it 

 would satisfactorily explain the variations in composition, texture and 

 richness. 



On the other hand, the absence of artesian conditions would account 

 for a deficiency or total absence of iron in limestone or sandstone strata 

 otherwise favorably located. In Niagara Gorge, where the Clinton strata 

 are well exposed, no ore seams outcrop. Otherwise, unaccountable breaks 

 in the continuity of the ore deposits could easily be explained by a failure 

 of the strata to provide good artesian runways or catch basins for the 

 iron-bearing solutions. 



AiiTKsiAN Replacement Tiiixiuy as Applied to Other Hoi;izons 



It is not likely that conditions favorable for the accumulation of iron 

 ore in the porous strata of artesian runways will hi' fouiul in any other 

 geological horizon on such an extensive scale as those of the Clinton. 

 The peculiarly favorable conditions resulting from tlu' rapidly changing 

 textures of sedimentary beds deposited in the Silurian Sea, and the periods 

 of cnistal movements, heavy precipitation and rapid weathering which 

 followed, furnished a most renuirkablc combiiuition of factors requisite 

 for the formation of great luunbers of artesian runways, with ample op- 

 portunity for subsequent filling. It is to be expected, however, that 

 artesian conditions will be found in manv horizons of marine strata at 



