150 
ONTARIO DIVISION. 
rapidly as those of Wayne, Orleans, Monroe and Niagara counties. The shales of the 
latter counties undergo the process sometimes called slaking , which consists in falling to 
a powdery state even when they are dry. The change, however, is far more rapid where 
they are exposed to an alternate action of atmospheric agency. It is almost impossible to 
prevent the decomposition of a piece of shale when it is wetted after having been thoroughly 
dried. This fact teaches us the mode by which they may be converted into renovators of 
the soil; for it is found that they contain several valuable salts, which are important in 
promoting the growth of vegetables. We shall recur again to this subject in another place. 
Minerals usually associated with the rocks composing this group. The most important 
mineral is the oolitic iron ore, which forms distinct strata by itself: it is a calcareo-argil- 
laceous ore, and is used for castings, but not for bar iron. Masses of chert, in which are 
cavities lined with quartz crystals, are not uncommon in the layers of limestone. Sulphate 
of barytes, of a red color, occurs in the oolitic iron at Wolcott furnace. Crystals of car¬ 
bonate of lime, sulphate of lime, pyritous copper and iron, and green carbonate, are 
sometimes found in several of the masses belonging to this group. 
Miscellaneous remarks. The most remarkable feature, as already observed, is the sudden 
and repeated changes in the mineral type of the layers and rocks which enter into this 
formation ; and perhaps the presence of those singular beds of iron ore, is not the least 
interesting of the facts connected with it. That a mass whose average thickness does not 
exceed one foot, should be spread out so extensively and by itself, unmixed with other 
matter, is a circumstance of great interest, and worthy of special investigation. The source 
of the iron is not well determined. In Jefferson and St. Lawrence counties, the red spe¬ 
cular oxide of iron is abundant; and the beds which are now open, exhibit the fact that 
they have at some former period suffered from denudation and transportation in a southerly 
direction, but this occurrence belongs without doubt to a period long posterior to the forma¬ 
tion of the oolitic iron. Still it is rational to believe that these northern beds may have 
furnished the materials for the iron of the Clinton group; and it is evident "that these 
masses were brought to the surface at a period subsequent to the deposition of the Potsdam 
sandstone, and the event may have happened in the era of the Clinton group. There is 
yet nothing discovered that militates against this view of the origin of the iron in question. 
The Clinton group is not confined to the State of New-York : it is found in Ohio, Penn¬ 
sylvania and Canada. Its thickness in New-York, according to Mr. Hall, does not exceed 
eighty feet. It is between fifty and sixty feet in Warren in Herkimer county. 
§ 2. Niagara group. 
Geodiferous limerock, and Calciferous slate, of Eaton ; Lockport limestone and Rochester slate, Upper part of the 
Protean group, of the Annual Reports. 
This name, as proposed, is selected from the place where the group is best developed, 
and where it not only is well situated to arrest the attention of the curious, but also occu¬ 
pies a point more generally visited than any other within the bounds of New-York. It 
consists of only two distinct members, and hence is comparatively a small group, or one 
which is composed of a small number of members. 
