CKEEFS IN COAL-MINES. 
19 
raines, that the roof is composed of hard shale, or occasional¬ 
ly of sandstone, more unyielding than the foundation, which 
often consists of clay. Even where the argillaceous substra¬ 
ta are hard at first, they soon become softened and reduced 
to a plastic state when exposed to the contact of air and wa¬ 
ter in the floor of a mine. 
The first symptom of a “ creep,” says Mr. Buddie, is a 
slight curvature at the bottom of each gallery, as at a. Fig. 
59: then the pavement, continuing to rise, begins to open 
with a longitudinal crack, as at b; then the points of the 
Fig. 59. 
Section of carboniferous strata at Wallsend, Newcastle, showing “creeps.” 
(J. Buddie, Esq.) 
Horizontal length of section 1T4 feet. The upper seam, or main coal, here worked 
out, was C30 feet below the surface. 
1. Main coal, 6 feet C inches. 2. Metal coal, 3 feet. 
fractured ridge reach the roof, as at e; and, lastly, the up¬ 
raised beds close up the whole gallery, and the broken por¬ 
tions of the ridge are reunited and flattened at the top, ex¬ 
hibiting the flexure seen at cl Meanwhile the coal in the 
props has become crushed and cracked by pressure. It is 
also found that below the creeps a, c, an inferior stra¬ 
tum, called the “metal coal,” which is 3 feet thick,has been 
fractured at the points 6,/*, A, and has risen, so as to prove 
that the upward movement, caused by the working out of 
the “main coal,” has been propagated through a thickness 
of 54 feet of argillaceous beds, which intervene between the 
two coal-seams. This same displacement has also been 
traced downward more than 150 feet below the metal coal, 
but it grows continually less and less until it becomes im¬ 
perceptible. 
No part of the process above described is more deserv¬ 
ing of our notice than the slowness with which the change 
in the arrangement of the beds is brought about. Bays, 
