222 
of-a-mile in breadth, each escarpment being from 90 to 120 
feet lower than the other, up to the northern edge, which is 
not less than 650 feet above the river-bed. The principal 
parts of these wide flat surfaces range between 900 to 1,100 
feet above the sea-level. 
The internal geological structure of Rombold's Moor and 
its outliers embraces strata occupying the interval between 
the Lower Coal Measures of Baildon Hill and the Mountain 
Limestone of Skipton. Near Skipton, on the side of Eom- 
bold's Moor, the Limestone is succeeded by the Yordale 
Shales and Grits, and the latter by the Millstone Grit. The 
Government surveyors have lately, as is well known, divided 
the Millstone Grit into at least four sub-formations. I have 
not yet been able to make out to which of these the highest 
strata of Eombold's Moor belong. Generally speaking, the 
Grits and Shales are approximately horizontal, but here and 
there deviations from horizontality are strikingly marlced. 
The general elevation of the strata may have been produced 
in a gradual manner, but there are abundant evidences of 
considerable convulsions at intervals; and whether the 
strata have been subjected to convulsions at one or more 
periods after their elevation or not, it is certain that they 
have experienced very violent movements ; especially is this 
evident in many places on the north side of the moor. 
Appearances warrant us in saying that they have been 
turbulently smashed, so as to leave great fractures, in addition 
to the regular joints or divisional planes. This may be seen 
in a quarry in a deep ravine a short distance south-west of 
Ilkley, and between this quarry and Ilkley, at a lower level, 
a section reveals strata dipping at a very high angle nearly 
southy or towards the moor. (See plate I., fig. 1.) Whatever 
amount of disturbance may have been experienced by the 
strata of Rombold's Moor and the valley of the Wharfe, it is 
certain that the present form of the surface is the effect of the 
