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» OF SOUTH CAROLINA. 13 
These rents and fissures, it will be observed, had a direction nearly at right angles with a line 
joining South Carolina, New Madrid, on the Mississippi, and Caraccas, the points where this earth- 
quake was most felt. It seems, then, that rents and fissures are produced at right angles with the 
line along which earthquake waves are propagated. The coincidence in direction between these 
rents and that of the trap dykes of the Atlantic slope is remarkable. 
Some Geologists have been led, from a consideration of the phenomena of earthquakes, to attri- 
bute the flexures and even the elevation of mountain ranges to earthquake waves. 
Having thus glanced at the probable origin of elevating foree and other igneous agencies, we may 
now return to the examination of some of their effects. Instead of the abrupt elevation and frac- 
ture of the strata, as represented in Fig. 2, we frequently observe a folding and contortion, caused 
by lateral pressure, which sometimes produces little more than gentle undulations. Fig. 3 will 
make this plain. | 
The upper part of these flexures, represented by faint lines in the cut, is often removed by denu- 
dation, and the corresponding lower portions are below the surface, so that we only see that part of 
the section represented by full lines. Such sections as these are fully exhibited between Edgefield 
Court House and the village of Abbeville; and generally the rocks below the mountains are thus 
turned up and contorted. ‘ 
This turning up, and consequent exposure of the edges of rocks, is a result of the utmost 
importance. It is indeed one of those beautiful contrivances which meet us every where in nature; 
remarkable alike for its simplicity and adaptation to the end to be accomplished. Had the rocks in 
the upper part of the State retained their original horizontal position, the clay slate, being the newest 
rock, would overlie the rest; and instead of the variety of surface and soil which it now presents, 
the whole country would exhibit a monotonous level, and be covered with the poor, grey soil of 
the clay slates. 'The beds of lime rock, the ores of iron, and the metals, would be placed far beyond 
our reach—nor would their existence even be known to us. But by this simple contrivance, we are 
not only presented with this beautiful variety, but the rocks are made to reveal their treasures for 
our use. 
The angle formed by the planes of stratification of a stratum and the horizon, is termed the dip, 
and the direction or course of the edge of the stratum is called the strike. 
4 
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