140 TOWN GEOLOGY. [vr. 



Look at any sea cliff in which the strata are twisted 

 and set on slope. There are hundreds of such in these 

 isles. The beds must have been at one time straight 

 and horizontal. But it is equally clear that they have 

 been folded by being squeezed laterally. At least, that 

 is the simplest explanation, as may be proved by 

 experiment. Take a number of pieces of cloth, or any 

 such stuff ; lay them on each other and then squeeze 

 them together at each end. They will arrange them- 

 selves in folds, just as the beds of the cliff have done. 

 And if, instead of cloth, you take some more brittle 

 matter, you will find that, as you squeeze on, these 

 f old will tend to snap at the points of greatest tension 

 or stretching, which will be of course at the anticlinal 

 and synclinal lines in plain English, the tops and 

 bottoms of the folds. Thus cracks will be formed; and 

 if the pressure goes on, the ends of the layers will shift 

 against each other in the line of those cracks, forming 

 faults like those so common in rocks. 



But again, suppose that instead of squeezing these 

 broken and folded lines together any more, you took 

 off the pressure right and left, and pressed them 

 upwards from below, by a mimic earthquake. They 

 would rise ; and as they rose leave open space between 

 them. Now if you could contrive to squeeze into 

 them from below a paste, which would harden in the 

 cracks and between the layers, and so keep them 

 permanently apart, you would make them into a fair 

 likeness of an average mountain range a mess if I 

 may make use of a plain old word of rocks which 

 have, by alternate contraction and expansion, helped 

 in the latter case by the injection of molten lava, been 

 thrust about as they are in most mountain ranges. 



