George Hickling—Folds and Overfolds. 507 
whole coast which I examined, from Combe Martin to the southern- 
most part of Bideford Bay, the axes of the minor folds are inclined to 
the north in this way, so as to frequently produce the appearance of 
steady southern dip and greatly to increase the apparent thickness of 
the strata. In speculating as to the possible cause of the constant 
direction in which the axes of these folds are inclined, an explanation 
occurred to me which I believe to be the correct one, and which may 
be applied generally to a large number of cases. As I have been 
unable to find it in the works I have been able to consult, it may be 
desirable to publish it, since it may aid considerably the elucidation of 
the true structure and history of complicated districts. 
The one feature in the structure of Devon which admits of no 
dispute is the broad syncline which comprises the whole county. On 
this broad fold those previously referred to are superadded, and from 
the parallelism of the two, and the fact that they were both formed 
after the Culm and before the Permian, it is almost certain that their 
formation proceeded part passu. How, then, would the form of the 
minor folds be affected by the fact that the whole area was at the 
same time becoming a syncline? It is obvious that in a synclinal 
fold the upper beds tend to be compressed, the lower ones to be 
extended. Both of these effects are resisted, and the result is a 
sliding of the beds relatively to one another on the sides of the fold. 
This may be illustrated admirably by an experiment described by 
Mellard Reade in his ‘‘Origin of Mountain Ranges’ (p. 210 and 
pl. xli). A number of strips of paper are laid horizontally, and 
their edges marked across with vertical lines thus :— 
Fic. 1.—Edge-view of pile of paper strips, with lines drawn across at right angles 
to the plane of the papers. (After Mellard Reade.) 
If the paper is now forced into folds, the displacement of the various 
layers relatively to one another is shown by the fact that the vertical 
lines are no longer vertical to the surface of the paper, thus :— 
Fic. 2.—The same papers folded, showing displacement of lines. (Modified after 
Mellard Reade.) 
The line starting at B, for example, instead of passing at right angles 
to the plane of the strips towards A, is displaced to A’. Now, if 
these vertical lines be assumed to represent the axial planes of minor 
folds, it is clear that those folds will become asymmetrical, their crests 
being forced outwards from the centre of the syncline. In a shallow 
syncline the displacement of these axes would only be slight, but, 
however slight, it would still exist, and would determine that the 
