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the paper into folds further to represent the net result of a complex 

 series of thrusts and strains affecting the rocks when they were 

 much nearer the centre of the earth than at present — and there is 

 an illustration of the nature and origin of faults in general, and 

 especially of the particular faults whose effects I am about to 

 describe. 



But it often happens that two or more faults may join at various 

 angles, and thus give rise to a line of fracture that is by no means 

 straight in its course. This further complication may be unravelled 

 by an extension of the last experiment. Run the cut out to the 

 edge of the copy-book at its lower margin, and continue the cut at 

 the other end a few inches off to the left, at rather less than a 

 right angle to the line of the original cut ; the incisions will then 

 represent the middle and upper limbs of the Z. Press the paper 

 on the left hand in the direction of the cut, as before, and in such 

 a way that the part lying to the right hand may this time remain 

 quite flat, while that on the left of the cut is bent into an upward 

 curve, arching above the general level of the paper at the point of 

 greatest curvature, and, at the inner angle of the incision, bent 

 down at the comer in such a way as to be depressed beneath it. 

 There will then be three points where any given sheet of paper will 

 be edge to edge with other portions of the same sheet, (that is to 

 say where there is no dislocation in a vertical direction,) and there 

 will be two points where the dislocation will be at its maximum. 

 If the separate sheets are coloured, or better still, are lettered 

 consecutively from a\o z, a on the left of the cut will be opposed 

 to a on the right; then as the paper arches upward on one side 

 while it remains fiat on the other, a point is presently reached 

 where z at the bottom, on the left, is opposed to a on the right. 

 We will call that a downthrow on the right hand. Then, as the 

 upward curve gives place to a curve in the opposite direction, y, x, 

 w, V, and so on, come in succession edge to edge with a, until 

 presently the point is reached where a and a are again together. 

 That is to say, at that point the vertical displacement is reduced to 

 nit. But the downward inclination being continued beyond that 

 point, the result is that a on the left of the incision is depressed 



