Torsion-Structure in the Alps. 263 



assume the form of confocal conies round an area of sub- 

 sidence, they tend to keep that form. 



Case 2. — Fig. 2 shows the result of the superposition of a 

 regularly-spaced system of radial corrugations on a regularly- 

 spaced parallel system. 



Fig. 2. 



ys7 



The resemblance of these curves to the spiral s or " whirl- 

 shaped " arrangement of the various Alps is undoubtedly 

 very suggestive. Here also, as in case 1, the superposed 

 system crosses the original system at all angles from 0°to 90°. 



In order not to confuse the figure I have shown only the 

 positive branches of the curves. 



As is shown in the appendix, the radial system cf corruga- 

 tions would require the forces, to which it would be due, to 

 have a direction at right angles to the radi i, and of magnitude 

 inversely as the distance from the centre. 



