GEOLOGICAL SKETCH 285 



period in which this bulk of h'mestone was deposited, 

 and place still further back in the depths of unrecorded 

 time the aoe of the oreater masses that lie beneath. 



We pass on. We climb the flanks of the hills to 

 reach the next zone, the bands of Jurassic and 

 Cretaceous rocks with their rich store of fossils. 

 Wedged in between the Trias and the thick Tertiary- 

 formation we come upon these strata. They lie in 

 narrow bands stretching from north-east to south-west 

 across the district. Softer in structure, more easily 

 denuded by the heat, the cold and the torrential rains, 

 they present a distinct contrast to the more compact 

 masses that lie above and below them. They seldom 

 stand out in bold relief They form no crag or 

 buttress on the hillside. More often are they hidden 

 rocks. Accumulations of soil, broken fragments of 

 stone and the less resisting products of erosion may 

 conceal them ; they may mark the lines of glens and 

 valleys that have carved them, or the course of a 

 narrow mountain path. Moisture lodges in their 

 substance, and, as it trickles through the fissile shales, 

 they crumble the more easily to decay. 



Though these Jurassic bands are narrow, but a few 

 hundred feet in thickness and insignificant compared 

 with the enclosing limestones, yet they are composed 

 of many and different layers. Beneath, resting 

 directly on the Trias, are black and fragile shales easily 

 split asunder. On every face of the severed rock we 

 see the lines and rusty blotches that mark the impress 

 of organic beings. We continue the search and more 

 perfect specimens appear, belemnites often in frag- 

 ments, a complete Pecten or Inoceramus with radial 

 or concentric sculpture still perfectly displayed. 



