304 Sir James Hall on the Consolidation of the Strata. [Oct. 



^bove described, of perfectly loose materials, traversed ver- 

 tically by a dyke, which, in its middle, consisted of whinstone, 

 and was flanked by solid conglomerate ; but this solidity abated 

 gradually till the conglutination of the rounded masses diminish- 

 ing by degrees, the state of loose shingle and gravel was entirely 

 restored on both sides. The agglutinated mass adjacent to the 

 'dyke bore no resemblance to the result of calcareous petrifac- 

 tion ; scarcely ever gave eftervescence with acid; and, by its 

 gradual termination, differed from any whinstone-dyke I have 

 seen to penetrate the strata ; for, in the ordinary case, the ter- 

 mination of the crystallite against the adjoining aggregate 

 through which it passes, is almost always quite abrupt. 



About a hundred yards higher up the valley of Aikengaw, 

 there occurs an agglutination similar to the last, though without 

 any whin-dyke, and sufficiently strong to resist the elements, by 

 which the surrounding matters had been washed away, leaving 

 the pudding-stone, or agglutinated shingle, to stand up by itself, 

 in a manner remarkable enough to have attracted the notice 

 of the peasantry as something supernatural, since they have 

 Ijestowed upon it the name of the Fairy's Castle. 



Farther up the stream, other agglutinations occur frequently, 

 as we could see in little narrow glens cutting through the mass ; 

 and higher still, they are so numerous as to meet and convert 

 the whole into one unbroken mass of pudding-stone, occupying 

 all that is exposed to view. 



These very remarkable, and, to me at least, novel appear- 

 ances, were the first which suggested the idea, that the con- 

 solidation not only of this class of conglomerates, but of sand- 

 stone in general, had been occasioned by the influence of some 

 substance in a gaseous or aeriform state, driven by heat into the 

 interstices between the loose particles of sand and gravel, where 

 it had acted as a flux on the contiguous parts. On considering 

 what this penetrating substance might be, and from whence it 

 could have come, the following circumstance presented itself to 

 my recollection at the moment, and promised to afford some 

 assistance to these conjectures. 



A few miles lower down the valley in which the above facts 

 were observed, at the distance of more than a mile from the sea, 

 and between two and three hundred feet perpendicularly above 

 it, there occurs a crag of sandstone, in wliich a numerous suc- 

 cession of strata are distinctly visible. Several of these beds 

 have yielded much to the action of the air, and, in dry weather, 

 exhibit a considerable white elflorescence, which has completely 

 the taste of common salt; and so remarkable is this circum- 

 stance, that the rock has acquired, in the country, the name of 

 Salt-Heugh. 



Here, then, it immediately occurred to me, was probably the 



