12 MR. J. E. MAER ON A C0NGL031EKATE ^ [Feb. 1 899, 



show unmistakable signs of being slickensided, though a few 

 scratches are found here and there which it would be difficult, 

 if not impossible, to distinguish from glacial striae. The following 

 features in connexion with these pebbles are noticeable : — ■ 



(i) The regular parallelism and closeness of the lines, in the 

 majority of cases. 



(ii) Erequent curvature of the lines. 



(iii) Grains of the matrix often firmly embedded at the ends of 

 the groovings. 



(iv) Deposit of mineral films on the grooved surfaces. 



(v) Fracture and frequent faulting of pebbles, the throw of the 

 faults being a fraction of an inch. 



(vi) Sudden commencement and ending of grooves at a fault- plane. 



(vii) Striae on adherent matrix in places. This feature was long 

 ago pointed out by Prof. T. McK. Hughes in the case of the pebbles 

 of homotaxial deposits near Sedbergh, and its significance was 

 insisted on.^ 



(viii) Slickensiding occurring on other planes beneath the surfaces 

 of the pebbles. 



(ix) Indentation of the pebbles, as the result of pressure. This 

 also occurs in glacial boulders, especially of limestone, but, so far as 

 lam aware, not on so extensive a scale as here. 



The pebbles in the two coarse conglomerates show the same 

 features, though they are best exhibited on the pebbles of the lower 

 accumulation. 



On removing a mass of the upper conglomerate, at the point 2 in 

 the section, the rock beneath (a coarse red sandstone with small 

 scattered pebbles) was found to be marked with groovings. There are 

 two principal sets of these, crossing each other at an angle of 

 abont 40°. Their directions were not observed, as the block ex- 

 tracted was carried for some distance to water before the striae 

 were rendered visible. The striaB appear to be impressed upon 

 crushed rock welded on to the sandstone, rather than upon the sand- 

 stone itself. Here again evideuces of slickensiding are clear, and the 

 parallelism of the striae, their closeness, their occurrence on more 

 than one plane, and the development of films over them is clearly 

 noticeable. Again, we observe a few scattered striations which it 

 would be difficult to separate from true glacial striae. The uneven 

 nature of the surface appears to be due to indentation by masses of 

 overlying rock. 



It will be noticed that the plane of discontinuity between the 

 coarse conglomerate and the underlying rock is absent to the left 

 of the section, or rather it curves down into the sandstone, so that 

 it is probably a plane produced by differential movement, rather 

 than one due to pause during deposition of the strata. The section 

 itself yields abundant evidence of the occurrence of diff'erential 



^ ' Notes on the Geology of Parts of Yorkshire & Westmoreland,' Proc. 

 Geol. Polyt. Soc. West Eiding Yorks, vol. iv (1868), No. 8, p. 570. 



