DU NOYER NOTES ON THE GIANT'S CAUSEWAY. 



9 



columnar beds ; they also become thinner, and lose their remarkable 

 parallelism of deposition, as well as distinct colnmnar structure ; 

 The upper one is now but rudely columnar, and the columns are 

 much thicker than those of the bed below ; the underlying ochre- 

 layer is wanting, and its place is supplied by a deposit of amorphous 

 basalt, which now attains a thickness equal to that of the super- 

 imposed columnar beds. This change of structure in the cliff-section 

 occurs in a distance of less than three hundred yards. Below 

 this amorphous basalt a new columnar bed of trap appears, the 

 pillars of which are exceedingly symmetrical in every respect, and of 

 great beauty ; they are exposed for the distance of about two hun- 

 dred feet, and are all inclined to the eastwards ; while their upper 

 surface, which is very even, slopes to the westward at about six 

 to eight degrees. This group of columns is called " The Organ" 

 (see figs. 4 and 5). 



Below this bed, though not absolutely seen, the missing ochre- 

 layer is presumed to be. If we now follow the cliff section west- 

 ward, we find that the " organ-bed" in its extension to that direction, 

 and with its dip of six to eight degTces would eventually be 

 brought so low that more than one-half of its thickness would be 

 emersed below the level of the sea, leaving the remainder to project 

 above the water, and thus to form that singular looking natural pier 

 called " The Giant's Causeway." At this spot the thickest and very 

 nearly the most central portion of this particular lava-flow is reached, 

 and it is worthy of remark that here the columns on the east side of 

 the Causeway, which is about one hundred and sixty feet across, in- 

 cline to the east, while on the west side they slope to the west, thus 

 showing in their vertical arrangement a radiation from a series of 

 centres, all following a given line, which would have very nearly a 

 meridional direction, or in other words that of the longest axis of 

 the lava-flow. This structure, I have no doubt, would be apparent 

 throughout the entire of this particular bed if we had the power to 

 examine it throughout, indeed the view which the cliffs afford of it 

 is almost conclusive on this point, as it exposes a transverse section 

 of it in two of its most important positions, viz., at the " Organ-" 

 columns, near its eastern termination, and at the Causeway, close to 

 its centre. 



VOL. III. B 



