4 
layers of rock, a foot or two in thickness, have been bent 
into the figure of an inverted W. The angles are sharp, but 
unbroken. You may easily test this on the ground by 
passing a finger over the apex of one of the bends. There 
is neither crack nor vein. 
I propose now to consider how this phenomenon can have 
been produced, and under what conditions rocks once hard 
and horizontally laid can be bent to an acute angle without 
fracture. 
Forty years ago it would have seemed natural to invoke a 
volcanic eruption acting upon plastic matter — to regard such 
folds and contortions as due to the formation or elevation of a 
kind of blister upon the earth's surface. But thanks to a 
few experimental inquirers, such as Sorby, Hodgkinson and 
Tyndall, a number of plausible suppositions have been swept 
away as fallacies. In 1867 the geologist looked rather to 
lateral pressure (due possibly to contraction of the figure of 
the earth) as most probably the force concerned, and he did 
not find it necessary to suppose that the distorted rocks had 
ever been plastic. It is true that Sir James Hall assumed 
that the rocks of Berwickshire were ductile when contorted, 
and Dr. Edward Hitchcock, a well-known American geologist, 
had recently maintained that some contorted pebbles in a 
conglomerate at Newport, Ehode Island, must have been as 
plastic as moist clay when they were bent and twisted. But 
this gratuitous assumption was soon disposed of. There were 
a few fossils in the Draughton limestone, and these were 
distorted like the rest of the rock. 
This seemed to prove that plasticity was not a necessary 
condition of contortion. The shells and corals had surely 
not been plastic. Indeed the matrix itself may well have 
been compact rock from the time of its deposition, growing 
by the addition of hard lumps and shells and films of stony 
calcareous matter. 
