10 
flexible limestones are very difficult to bend permanently. 
One specimen exhibited for many years in a public museum, 
with the two ends supported and the centre slightly depressed 
to show its flexibility, does not present any visible deflection 
when placed on its edge. 
Thin natural laminae of flagstone from the coal measures 
were also tried. Various specimens were selected according 
to their texture and mineralogical character, but none yielded 
important results. It will be seen further on from other 
evidence that considerable deflection has been unintentionally 
produced in these flagstones, but as yet I have never succeeded 
in bending thin plates more than 8'. Slates of various kinds 
have also proved very intractable, an interesting and not 
unexpected result. N"o material has yet done so well in my 
hands as carefully cut slabs of mountain limestone 4 in. x 3 in. 
and '07 in thickness. 
The frequent destruction by spontaneous fracture of bent 
plates when removed from the machine seems to imply that 
an indefinitely protracted and uniformly contorting force is 
needed to produce unbroken curvature, such as that on the 
coast of Berwickshire. The experiments next to be related 
tend to show that resistance on all sides diminishes the risk 
of fracture. While designed to answer other purposes, the 
precautions described and the result attained serve to 
strengthen the opinion that unbroken anticlinals and syn- 
clinals are only formed under a considerable weight of 
superjacent strata. 
Anxious to imitate the natural condition of lateral pressure 
more closely, and at the same time to preserve well- contorted 
specimens for reference, I tried another method, which ulti- 
mately yielded interesting results. My object was to apply 
pressure to the edges of a slab of stone and overcome the 
tendency to fracture by embedding it in a matrix of some 
tenacious substance* The precaution was especially necessary 
