1 8 . Kinahan — Weathering of Rocks. 



undisturbed, and its own fracture quite structural, and connected 

 with the crystalline elevation and starry concretion above. I have 

 no idea at present why the central portions of these concretions of 

 dark amethyst are partly terminated by right lines, or what deter- 

 mines the greater number of bands on one side than on the other. 

 The second figure is of a less varied, but of still more curious in- 

 ter st. There is no trace of violence or fracture in the stone, and the 

 line of the crj^stallized amethystine mass is undisturbed at the sum- 

 mits, except by a partial dissolution in one part and mingling with 

 the white bands above. But the white undulatory band at its base 

 is cut into three parts, and the intermediate portion lifted (or the 

 flanks removed downwards), a quarter of an inch, by pure calm crys- 

 talline action, giving thus room for an interferent brown vein of less 

 definite substance which proceeds without interruption, dividing 

 the white band in a direction peculiarly difficult to explain, unless 

 by supposing the interferent one to be the slow filling of a fissure 



originally opened in the direc- 

 tion of the black line in Fig. 8, 

 Fig. 8. and straightened in widening. 



But the third example is inexplicable, by any such supposition. 

 It is the agatescent centre of a large amethyst nodule, in which a 

 small portion, about the third of an inch long and a quarter of an 

 inch thick, of its encompassing belt, is separated bodily from the rest, 

 taken up into the surrounding concretion of quartz, and its place 

 supplied by a confused segregation of chalcedony, with a sprinkled 

 deposit of jasper spots on the surface exposed by this removal of its 

 protecting coat; spots, which in the rest of the stone, form on 

 the exterior of the coat itself, just under the quartz. There are many 

 points in all these three examples which it is useless to take further 

 note of at present, but to which I shall return, after collecting 

 examples enough to form some basis of reasoning and comparison. 

 I must apologize, as it is, for the length of this paper on a subject 

 partly familiar, partly trivial, yet in which these definitions, not by 

 skill of mine expressible in less room, were necessary before I could 

 proceed intelligibly. 



-^^^^./W./'V/ 



V. — Notes of the Weathering of Eocks near the Sea. 

 By G. Henry Ktnahan, F.R.G.S.I., Etc. 



THE following notes on the Weathering of Rocks near the Sea, 

 culled from my note-books, appear to be facts unobserved by 

 the various writers on subaerial denudation. Those agents would 

 seem to act difierently near the sea than away from it, not only in 

 the quantity of the work done but also on the colouring matter in the 

 rocks. 



As to colour, I find — '' In the neighbourhood of Valencia, Co Keriy, 

 the weather seems to have mostly affected the red colouring matter 

 in the rocks for those of a purple colour, weather a whitish blue, 

 while those of a green colour only become brighter ; inland, the 

 purple rocks are weathered red, and the green yellow ; so that, there 



