COAL FORMATION. A481 
square rods, covering the lower layer of bluish sandstone, which is 
not at all fissured to correspond with the ironstone. Below three 
inches of the sandstone, there is another layer of ironstone similar to 
the one just described, and lying upon a thick layer of the same solid 
bluish sandstone. The walls of the larger areas extend through the 
whole thickness of the ironstone layer; but not so those of the smaller, 
which are often very irregular; and hence the upper and under sur- 
faces generally have but little resemblance. 
Within the areas, the rock is laminated and slightly concentric ; it 
is rather soft, and is worn out to a considerable depth, (often nearly 
an inch,) producing a honeycomb texture. ‘The walls are hard, and 
consist of clay ironstone. 
Calcareous Prismatic Concretions.—Various specimens of remark- 
able prismatic forms of lime were presented us by Mrs. Robert Scott 
of Glendon. ‘They were described as occurring in clay ; but whether 
they pertain to the sandstone rocks under consideration is not yet 
determined. As these rocks occur at Glendon, this is their most pro- 
bable source, and we therefore mention them in this place. The facts 
as to their characters are the same, whatever be their place of origin. 
Two of these singular crystals are represented in the following 
figures, much reduced. Some of the crystals are twenty inches long ; 
Fig. 2. 
three or four inches is the average size. They have a rhombic form, 
and taper towards each extremity, the two ends curving slightly in 
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