1845.] Diluvial and Wave Translation Theories. 235 



In some places on the sides of the hills, the ends of the limestone 

 beds protrude in steps about a foot high, down which the rain water 

 has evidently flowed in a series of miniature cascades, which have 

 hollowed out on the slabs below little cavities, and depressions not 

 unlike the lapiaz of the Alps, marked by a a in the subjoined section- 

 al diagram. (Plate, Diagram, No. I V.J 



Variolated surfaces. The surface of some slabs exposed to the air 

 I observed to be perfectly variolated with circular, shallow cavities, 

 caused by the dropping out of cubic crystals of iron pyrites. These 

 crystals may be seen in every stage of decomposition, — first tarnishing, 

 and losing their bright metallic lustre ; next passing into a bronze- 

 coloured hue : they then become liver-coloured, and lastly pass into 

 a loose rust-coloured dust. At this stage, the limestone becomes 

 stained by the rust nearly in semi-circles, marked a a a a, on each 

 side of the crystal marked b, in the Diagram b, representing the de- 

 composing crystal of pyrites. (Plate, Diagram, No. V.J 



In the next stage, the angles between a a a a, become discolour- 

 ed, and the whole stain takes a circular form ; then the centre occu- 

 pied by the crystal drops out, and finally the whole circular space, 

 occupied by the rust-coloured stain. 



Mark of ancient rains. Surfaces of rock variolated with such 

 cavities must not be set down as having been indented by an " ante- 

 diluvian shower," though marks exactly similar to those supposed to be 

 the effects of ancient rains exist on slabs below the surface covered 

 by other layers, the lower planes of which exhibit the casts of these 

 impressions. 



Ripple marks. Ripple marks are seen in similar situations to the 

 rain-drop impressions, but are much more frequent in the associated 

 sandstone. 



Strice and Furrows on granite and gneiss. Striae and furrows on 



granite, gneiss, &c. in situations beyond the reach of present aqueous 



causes are rare, and, from their conforming to the hard and softer parts 



of the rock, cannot be set down as marks of glacial action. These 



rocks, as before observed, are much subject to exfoliation by atmospheric 



exposure; consequently ancient marks, if they did exist, are liable to 



early obliteration on the air-exposed surfaces of such rocks. 



2 L 



