120 



J. Altken — On Faults in Drift. 



(although Professor Hull declines to offer a decided opinion upon 

 the subject) may, I conceive, be satisfactorily accounted for on the 

 following ground, without having recourse to the supposition of 

 their having been caused by the disturbance of the subjacent Palaeo- 

 zoic strata, an hypothesis which the author seems inclined to favour. 

 During the time the section was exposed I had frequent oppor- 

 tunities of visiting the spot, when my attention was attracted to 

 the disturbed condition of the beds, the nature of which was 

 described in the notice referred to. The section occurred on the 

 face of what was formerly a steep slippery bank of considerable 

 elevation, at the foot of which the river Eoach now runs, and at a 

 place where that river formerly made a considerable bend to the 

 south of its present course : thus giving rise to a sort of obtuse 

 promontory, around two sides of which the water would then flow, 

 and against which it would in times of flood be projected with con- 

 siderable force, and that too at a time when it was not confined to a 

 particular course by artificial means. Under these circumstances it 

 is more than probable that the faults here observed are attributable 

 to the undermining and destructive influence of the water at the 

 base of the cliff, aided by the percolation of the surface water and the 

 soft loamy and clayey character of some of the beds, causing a series of 

 subsidences or land-slips to take place. The force of this supposition 

 will be rendered more apparent by referring to the explanatory 

 sketch accompanying Prof. Hull's paper, where the strata are repre- 

 sented as being let down by three successive steps in the direction 

 of the river. 



Whether this view be accepted or not, I trust it will be found 

 deserving of careful consideration as offering a feasible and probable 

 explanation of the phenomena. 



The sketch of the section, given on page 119, although not drawn 

 exactly to scale, is approximately correct. 



EXPLANATION OF SECTION ON PAGE 119. 



No. 1. Eed sand with indistinct wavy lines of bedding 



2. Argillaceous sand ... 



3. Sand with a thin layer of fine gravel at the bottom, resting on 



No. 2., containing water-worn bits of coal 



4. Argillaceous sand 



6. &6. Sand 



7. Fine gravel 



8. Fine sand with irregular discoloured lines running through it 



9. Stiff brown clay inclosing boulders and pebbles much mottled 



with green streaks and patches ... 



10. Sand, in places mixed with gravel ... 



11. Clay, with a few pebbles 



12. Sand 



13. Fine Gravel (say 2 to 3 feet thick) 



ft. 



in 



6 









3 



1 









3 



2 









3 



5 



6 



3 







2 







1 







2 



6 



2 



6 



Total 25 



