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32 TRANSACTIONS OF THE [oer. 1%, 
layer has been crumpled up against the huge abutting mass of 
distorted gneiss which makes up the base of East Mountain, has 
been soldered together into a rock of extraordinary compactness 
in which the original slaty structure has been almost entirely 
obliterated. d 
In addition to the secondary bedding structure, by which the 
stone, especially at its eastern outcrop, is divided into thick and 
nearly horizontal layers, we also find many nearly vertical fis- 
sures, running about N. and&., ¢. e., with the strike and lamina- 
tion—evidently remnants of the old bedding-planes of original 
deposit. There is besides a cross-set of strongly marked master- 
joints, trending nearly E. and W. (EH. 10° N. or E, 10°S. to 
W.10° S. or W. 10° N.). By these numerous division-planes the 
mass of the rock is naturally cut up into huge blocks, oblong 
and angular. In many of them, near the surface, the rounding 
off of corners, by subterranean decay, has converted the form 
into that of elongated, often egg-shaped boulders. The results 
of these planes of subdivision can be readily seen in an ordinary 
quarried block of the stone. 
First, its elongated or sometimes flattened, slab-like shape in- 
dicates the regular horizontal bedding, the position in which it 
lay before it was hewn out—the ‘‘ bed,” ‘‘ free grain,” or “‘ rift ” 
of the quarrymen. ‘The stone cleaves easily parallel to the 
broader flat faces of such a block. 
Secondly, the stone cleaves less readily in another direction, 
vertical and at right angles to the former, which is generally 
shown by two even faces at opposite ends of the block. This 
was originally caused by the horizontal thrust of the folded 
strata, and marks the ‘‘cross-grain” of the quarrymen. 
Thirdly, a series of dark gray and grayish-white lines and 
bands, straight or zigzag, over four faces of the square block, 
indicates only the edges of the lamination-plates, marking the 
lines of the original horizontal deposit of successive thin layers 
of sediment. With the exception of certain slates and granytes, 
these lines would show in ether rocks, e. g., sandstones and 
limestones, the present surface of bedding and of easiest cleav- 
age. The exception in this case is almost unique among the 
magnesian limestones or dolomytes. The original slaty struc- 
ture has been obliterated by the subsequent folding and pressure, 
and there is no longer any tendency to cleave in this direction— 
the ‘‘ mock grain ” ‘of the quarrymen. The distinction between 
these three directions is of the utmost practical importance ; 
since past experience with other stones always inclines a stone- 
cutter to attempt to cleave such a stone in the last direction or 
‘‘mock grain,” with the result of loss of labor and often the 
waste of a valuable block. 
