14 Jackson, Facetted Pebbles with Glacial Deposits. 



EXPLANATION OF PLATES I. and II. 



Figs, i to 14. Facetted and Wind-worn Pebbles. Pendleton, Lanes. 



iths Nat. Size. 



Plate I. 



Fig. 1. — Coarse indurated ash with large quartz grains : upper 

 surface showing two main facets, both of which show 

 evidence of wind-erosion. The angle is probably due 

 to erosion. 



Fig. 2. — Very fine compact sandstone : the facet is a wind- worn 

 split face ; the splitting almost coincides with the 

 lamination planes. The whole stone, including the under 

 surface, shows signs of sand-blast. The angles are clearly 

 due to fracture. 



Fig. 3- — Very fine compact sandstone : upper surface showing two 

 facets ; one (the upper) is probably a split face smoothed 

 by blowing sand, the other (lower) is the original surface 

 of the pebble with the lamination planes slightly accentu- 

 ated by wind-erosion. This pebble is also facetted on 

 its under surface. 



Fig. 4. — Very fine compact sandstone : upper surface showing 

 three main facets ; the lower facet faced N.W. when 

 in situ. The left-hand facet coincides with the lamina- 

 tion planes. The under surface is water-worn. The 

 ■ typical " dreikanter " form is clearly due to fracture. 



Fig. 5. — Very fine compact sandstone (bedding not perceptible) : 

 an irregularly facetted form. The under surface shows 

 numerous glacial strise in a longitudinal direction. 



Fig. 6. — Very fine compact sandstone (bedding not perceptible) : 

 upper surface showing modified split face ; remainder 

 of stone is worn smooth by sand-blast. The angle is 

 clearly due to fracture. 



Fig. 7. — Fine gritty ash : upper surface showing five incipient 

 facets and flat top, all differentiated. The under surface 

 is quite flat and shows glacial striae in various directions. 

 There is no clear indication that this form has here been 

 determined by splitting. 



Fig. 8. — Very fine compact sandstone (Kirkby Moor Flag?): a 

 typical " dreikanter," showing the relation of one of 

 the three facets to natural planes of fracture due to 

 recent frost-action by which the pebble has been broken. 

 The fractured face (to left) would seem to have suffered 

 considerable wind-erosion. 



Fig. 9. — Fine compact sandstone : upper surface showing four 

 facets and the picking out of bedding planes by wind- 

 erosion. The facet to left coincides with the bedding 

 planes. This pebble was found in situ in an inverted 

 position. 



