CiRC. No. 79. 



Books and Maps. 



The whole district is comprised in Sheet 95 N.W. of the One-inch 

 (and Sheet 47 of the Six-inch) Ordnance Map, which may also be had 

 geologically coloured. Tate and Blake's 'Yorkshire Lias' — which 

 gives sections of Robin Hood's Bay — is the chief authority ; see also 

 the Geological Survey Memoirs, Baker's ' North Yorkshire,' PhilUps' 

 'Geology of the Yorkshire Coast,' and 'The Yorkshire Oolites' (Proc. 

 Geol. Assoc, Vol. iii. No. 7). 'The Naturahst' for Aug. and Sep., 

 X.888, pp. 239 and 265, contains much information on Botany, in the 

 form of lists (including flowering plants, mosses, and hepatics), by 

 M. B. Slater, F.L.S. and Prof C. C. Babington, M.A., F.R.S. 



Physical Geography and Geology. 



Mr. W. H. Hudleston states that this excursion affords a favourable 

 opportunity for the study of portions of the Lias and Inferior Oolite. 

 Many of the zones of the Lower Lias are well displayed in the scars 

 uncovered at low water, which conform more or less to the general 

 curve of the Bay, of which the Peak forms the 'South Cheek. 

 According to the Geological Survey mapping the effect of the Peak 

 fault on these scars is to throw the beds of the zones of Am. armatus 

 and Am. oxynotus against the margaritaius-hed.?, of the Middle Lias, 

 which latter constitute a projecting tongue of rock enclosed within a 

 fork of the fault. The frontispiece to Young and Bird's ' Geol. Survey 

 of the Yorks. Coast ' represents ' a view of the remarkable break in 

 the strata at Peak' as seen from this projecting tongue of rock, which 

 may be said to separate Robin Hood's Bay from Blue Wyke Bay. 



In the cliff itself the effect of this great fault is to bring the Middle 

 Lias into juxtaposition with the Lower Estuarine Series of the Inferior 

 Oolite, the beds on the down-throw side curving towards it, but 

 ultimately assuming a strong dip in the opposite direction, i.e., S.E. 

 Peak Hill, about 600 feet in elevation, is in great measure the result 

 of this fine stratigraphical feature. It thus possesses a certain 

 resemblance to Scarborough Castle Plill, whose northern precipice is 

 due to a fault having a similar direction. But in the case of the 

 Castle Hill a cross fault has helped to wedge out the entire mass 

 from the adjacent country, which is not so at the Peak. In each case 

 the hill is on the down-throw side, but the removal of the up-throw 

 side at the Peak has been less complete than at Scarborough. The 

 throw of the Peak fault is about 400 feet. 



The summit cutting of the railway does not show a section of the 

 fault, but its eff'ects are seen on the down-throw side by the strong 

 curveinthe beds of the Middle Estuarine, whilst a short distance towards 

 the north, the ' alum shale' or cojnmunis-hed.?, are observed in the 

 next cutting. An interesting section in the old alum quarry close by 

 (Crag Hall) displays the ' alum shale ' surmounted by the Dogger, 

 here only four feet thick, which is succeeded by the Lower Shale and 

 Sandstone (Lower Estuarine). A peculiar feature in connection with 

 the development of the Jurassic rocks of this district is the attenuation 

 of the Dogger and carrying Sandrock,the total absence oi xh& striatulus- 

 or: Jurensis-h&ds, and a probable loss of a portion of the co7trmunis-htd.s, 

 all of which are seen to be largely developed on the down-throw side 

 of the fault in the Peak, not quite half-a-mile distant. 



