Penny Blood: Serial Sensation and Working-Class Entertainment — page 228: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

CH. XVI. | ON FAULTING. 21! ., 80 that when contraction has proceeded to a small extent, the end a, of the ruptured stratum has moved further from its original -position #, than a, has moved from the same place. Now let the stratum B,B, crack. It is probable that it will crack at /, half way between a, and a,. At any rate, the probability that it will crack to the right being the same as that it will crack to the left, for a large number of layers the average position of the crack will be central. Now, if the thickness of the strata be indefinitely diminished and their number indefinitely increased, we get the actual circumstances of the formation of the fissure, and the locus of the points F’,, F,, &c. is the axial surface; and it 1s obvious that if our demonstration be admitted it will hade to the downthrow, because the beds which contract most in the horizontal direction will also contract most in the vertical and form the downcast side of the fault. The fault itself would also have its throw and its hade in the same direction as the fissure, and would run on slantingly downwards until it reached some stratum or massive rock which did not contract at that place, or where unconformity occurred and contraction had previously been satisfied in the underlying beds. It would seem that vertical rather than horizontal con- traction (though the two would go on together) determines the course of faults. For horizontal contraction would tend to divide a country into polygonal areas like a bed of basaltic columns, but faults run in approximately straight lines. Now this is the direction followed by a crack which is formed by the depression of a lamina as may be observed in the case of ice. When one first steps on a sheet of ice that has never been disturbed it is usual to notice a crack run with a ringing sound, quite, or nearly, across the surface in a straight line from beneath one’s feet. This is of the nature of a fault and is another instance of the analogy between the behaviour of ice and the strata of the earth's crust. We propose therefore to explain the phenomena of faulting 14—2 GONG oOo SS (CO)