178 Kendall: Notes on the Robin Hood’s Bay District. 
Peak Fault seems to belong to a system of dislocation 
completely surrounding the folded, but not faulted, mass of the 
Cleveland Hills in much the same way that the Craven and 
related faults surround the unfaulted mass of Carboniferous 
rocks of the Yorkshire Dales. The analogy may be traced 
even further, and just as it has been argued that contempor- 
aneous movements of the Craven system of faults affected the 
deposition of the Carboniferous and Permian rocks, so, and 
with even greater clearness and certainly, it can be inferred 
that the Cleveland system of faults affected the deposition of 
Jurassic and Cretaceous sediments. It is not improbable that 
the Cleveland phenomena are the actual complement of those of 
Craven, and that if either the secondary rocks had been partially 
preserved in the western area, or the paleozoic rocks exposed 
in the eastern one, we might see that repetition of movements 
of the dislocations had continued intermittently from Car- 
boniferous times, or earlier, down to Cretaceous times, or later. 
It can be readily demonstrated that some of the folds were lines 
of persistent movement. 
The Peak Fault, which belongs to the same series as the 
Speeton Fault and the dislocation that runs across the peninsular 
ot Scarborough Castle, has long been a subject of speculation 
among geologists, and within the last two or three years Mr. 
Rastall and Mr. Herries have both written on the subject. The 
feature to which most attention has been directed is the effect 
of the fault upon the contrasted development of the Upper Lias 
and Lower Oolites upon opposite sides of the fault. 
On the downthrow (seaward) side the Dogger shows a very 
large development, and includes important fossiliferous marine 
beds, and the Blea Wyke beds and the Lytoceras jurense beds 
are of great magnitude. While on the upthrow (landward) side 
the succession, which is splendidly exposed in the great range 
of old Alum Works extending from Peak Tunnel to Stoupe 
Brow, shows a greatly attenuated Dogger, consisting of only a 
few feet of sandstone, with some inches of basal conglomerate 
resting on the Alum Shales of the Upper Lias, the jwvense zone 
and the Blea Wyke beds being absent. Various explanations 
of the discrepancy have been offered, and they will form 
excellent provocation to those dialectic encounters for which 
the geologists have long been renowned. i 
Glacial Geology will, no doubt, have its day, and if there 
should chance to be a geologist present whose jaded palate can 
still respond to the stimulus of glacier lakes and overflow 
Naturalist, 
