50 



It' lime is present in the shales, this will react with the ferric sulphate 

 to form calcium sulphate and ferric oxide; the latter being insoluble, 

 will he deposited where formed.* The reaction is: 



I\(S(),) IICU'O; 3CaS0 4 Fc.o, :Klf. 



The calcium sulphide will he hydra ted and deposited as gypsum, as was 

 noted in some portions of the Upper Moscow shales. 



The ferrous sulphate may react directly with the calcium carbonate of 

 the shales, giving calcium sulphate and ferric carbonate. The former 

 is hydrated and deposited as gypsum, while the ferrous carbonate is 

 carried off" in solution. This may account for the absence of much iron 

 stain on the shales in which the gypsum crystals are formed. Eventu- 

 ally on exposure to the atmosphere, the ferrous carbonate will oxidize 

 to insoluble ferric hydrate, which will be deposited. 



Concretions are not uncommon in this shale. They are 

 usually of iron pyrite, or at least have a pyrite nucleus. 

 Occasionally they have a septarian structure, with veins of 

 crystalline calcite, siderite, or more rarely, barite. The gray 

 Naples or Cashaqua shales, appear between the Genesee 

 below, and the black Naples or Gardeau shales above. They 

 are readily recognized by their gray color, the numerous 

 rows of concretions, and the sloping, more or less weathered 

 face which they present. The rocks above and below form 

 perpendicular banks, and consequently whatever vegetation 

 grows on the face of the cliff, is chiefly confined to the por- 

 tion formed by the Cashaqua shales. The upper ( Gardeau ) 

 shales, are exposed in the first half mile of the cliff, after 

 which the\- are absent for a greater distance, the banks 

 decreasing to less than half their original height. 



This decrease in height begins at the "uplift," a thrust 

 fault of considerable magnitude, when the general undis- 

 turbed character of the strata of this region is taken into 

 consideration. The fault appears in a recession ot the bank, 

 which is due to the weakening of the strata by the fault, and 

 consequently the greater readiness with which they succumb 

 to the attack of the waves. The vertical displacement of the 



•In this manner shells are often entirely replaced by limonite, 



