IN THE SOUTH-WESTERN COUNTIES. 55 



disclosed a section consisting of bluish-grey (? Devonian) shales 

 faulted against Triassic sands. At the fault the shales are curved 

 into an S-shaped form. If this section merely revealed the upper- 

 most curve of the shales, any one on the look-out for terminal 

 curvature as a proof of ice-action would accept it as an additional 

 sign. 



Fig. 2 shows a sketch section of a road-cutting between Great Tor- 

 rington and Bideford, in which numerous faults are exposed ; ter- 

 minal curvature, probably due to the intrusion of fault rock, is 

 exhibited. 



The Culm-measures of North Devon, near Torrington, Eggesford, 

 Merton, &c, are often flexed at such acute angles that the detec- 

 tion of faults by dip, unless shown in section, is impossible. By 

 the road from Exeter to Cowley Bridge the Culm -measures exhibit 

 an extraordinary amount of flexure. Near Holcombe Burnell * flex- 

 ures from proximity of faults, fan-shaped structure, &c. are visible. 

 These are a few of many instances which 1 might cite as examples. 



The second cause assigned is the intrusion of wedging frosts 

 between the laminae of shales, leaving earthy matter filling up the 

 gaps produced by them, on the approach of summer. This has 

 been advocated by Mr. Godwin- Austen f in explanation of a section 

 of contorted shales at Gurrington, near Ashburton. I have seen 

 counterparts of the section he gives in illustration in many parts 

 of the Culm-measure area. In times past, judging from evidence of 

 a more rigorous climate furnished by the Head, searching frosts 

 may in many cases have produced superficial curves and contortions 

 in soft shales. 



The third and most common cause of strictly superficial curvature 

 is the intrusion of .roots acting as wedges. The hedge banks of 

 Devon afford many examples of this action in the Palaeozoic area ; 

 and the continuity of the layers in the Triassic pebble-bed is often 

 broken from a similar cause. 



Near Newton Abbot a road-section, of which I give a sketch 

 (fig. 3), was pointed out to me by Mr. H. B. Woodward. The 

 surface-curvature is partly due in this case to the intrusion of 

 roots ; but the general contortion is apparently due to a more 

 deep-seated cause. 



In conclusion I would suggest the possibility of surface -curva- 

 ture having been produced in spots where no roots can now be 

 found, by the intrusion of the latter, though subsequent decay has 

 left no other trace of their former existence. 



* Tn Ordnance Sheet 22., S.E. of Exeter. 



t Trans. Geol. Soc. 2nd ser. vol. vi. part 2, p 437. 



