THE MENDIPS : A GEOLOGICAL REVEEIE. 



245 



cvorywliore a similarity of conditions that enabled thorn to 

 flourish and survive without change or variation. For, as 

 Mr. Jukes-Browno well remarks, " when the seas wore 

 shallowed by the continued deposition of material derived 

 from tho continents, and when the higher land was every- 

 where encircled by a wide bolt of low-lying jungle and 

 swampy ground, intersected by sluggish waterways and 

 lagoons, the conditions would be exactly those where nature 

 would present a monotonous and uniform aspect, and whore 

 the plants and animals which had established themselves 

 would be likely to maintain their existence unchanged so 

 long as the same conditions prevailed." 



But thi3 period of quiescence, protracted as it was, could 

 not last for ever. It was succeeded by an epoch of severe 

 earth-throes. Pressure set in both from the north and 

 south, and from the east and west; and the strata that had 

 accumulated under conditions so peaceful were squeezed be- 

 tween the jaws of tho surrounding continental lands. By 

 the gradual and resistless pressure thus brought to boar 

 upon them the horizontal deposits were thrown into ridges, 

 some running east and west, some north and south, just as a 

 piece of cloth puckers up in ridges when the ends are 

 pressed together. One of the most marked of the oast and 

 west ridges is that of the Mendip Hills, which then had 

 their birth after their prolonged period of gestation in the 

 womb of tlie carboniferous seas. And perhaps a great 

 igneous dyke which pierces the Old Eed Sandstone near 

 Stoke Lane may have been formed at the period of this up- 

 heaval. Of the north and south ridges, the Pennine chain, 

 sometimes called the backbone of England, is one of the 

 most conspicuous. In the basin-shaped or oval troughs 

 between tho ridges, the coal measures wore preserved from 

 that destructive denudation wrought by rain and frost, by 



