BY HUGH MILLEE. 353 



No mere weathering, it seems to me, could form siicli holes, 

 which, I may say, were not associated with the rusty cores to 

 be occasionally remarked in limestone. On the other hand, so 

 complete a shelter might well be sought as such. Slugs and 

 snails, even without doing any active boring, would concentrate 

 moisture at the inner end of the cavities, and so promote their 

 elongation by solvent action. If this be the proper view, the 

 first beginnings of the holes were due to weathering : the deep- 

 est dimples were then selected as resting places or shelter by 

 some wet-bodied animal, and there was thus brought to bear on 

 their elongation the moisture otherwise excluded. 



Conclusion. — In one of the limestone, quarries you may find a 

 coralline, — an exquisite piece of filagee, with the stone dissected 

 away from it as no human hand, or finest instruments have deli- 

 cacy to dissect, — every mesh perfectly opened, every thread pure 

 white. The same power of waste, carving that stone lace- work 

 into its minute tracery of threads and meshes, has cut out this 

 Tynedale region into most of its diversity of heights and hol- 

 lows, — from its pot-holes and swallow-holes up to its ribs of 

 escarpment. A varied sculpture is the inseparable accompani- 

 ment of the gradual working down of drainage basins into the 

 body of the country. There is a sort of evolution in the process. 

 The river, its larger and lesser branches, and its minute capillary 

 feeders, although constituting one great eroding machiuc, have 

 neither equal powers, nor simultaneous opportunities, for exca- 

 vation ; and long after the main stream in its lower reaches has 

 worked its bed down so close to the level at which it enters 

 the sea, that gradients have become low, and action sluggish, and 

 the processes of carving are more and more retarded, and the 

 features, which are the monuments of active erosion, grow worn 

 and vague, like the mouldings on any old bit of sculpture, — the 

 golden age of force, activity, and opportunity has passed to the 

 higher regions. 



In this paper wc have seen only one side of Nature's geolo- 

 gical balance — that side which persistently lowers towards tlie 



