G. W. and F. M. Balfour — On the East Lothian Coast. 161 



age there occur, according to Mr. God win- Austen, some large ice- 

 transported blocks. This seems to me to have been the period when 

 the Eeindeer frequented Britain and the South of France, and that 

 to which so many of our river gravels belong. 



Whether any geologists may be disposed to agree in the view 

 which I have put forward or not, the question I think demands in- 

 vestigation ; and the more this is attempted, the more, I think, 

 geologists will become satisfied of the greater remoteness of the true 

 Glacial period, and of the far longer duration of the Post-glacial, than 

 has been hitherto supposed. 



IV. — On some Points in the Geology of the East Lothian Coast. 



Ey G. "W. and F. M. Balfour, 



Trinity College, Cambridge. 



THE interesting relation between, the Porphyrite of Whitberry 

 Point, at the mouth of the Tyne near Dunbar, and the adjacent 

 sedimentary rocks, was first noticed, we believe, by Professor Geikie, 

 who speaks of it in the Memoirs of the Geological Survey of East 

 Lothian, pages 40 and 41, and again in the new edition of Jukes's 

 Geology, pp. 269. The volcanic mass which forms the point, con- 

 sists of a dark felspathic base with numerous crystals of augite : it 

 is circular in form, and is exposed for two-thirds of its circum- 

 ference in a vertical precipice facing the sea, about twenty feet in 

 height. 



The rock is traversed by numerous joints running both in a hori- 

 zontal and in a vertical direction. The latter are by far the most con- 

 spicuous, and give the face of the cliff, when seen from a distance, 

 a well-marked columnar appearance, though the columns themselves 

 are not very distinct or regular. They are quadrangular in form, 

 and are evidently produced by the intersection at right-angles of 

 the two series of vertical joints. 



It is clear that the face of the precipice has been gradually receding 

 in proportion as it yielded to the action of the waves ; and that at a 

 former period the volcanic rock extended considerably further than at 

 present over the beds which are seen to dip beneath it. These latter 

 consist of hard fine-grained calcareous sandstones belonging to the 

 Lower Carboniferous formation. Their colour varies from red to 

 white, and their prevailing dip is in a N. W. direction, with an average 

 inclination of 12-20°. If the volcanic mass is a true intrusive rock, 

 we should naturally expect the strata which surround it to dip mcay 

 in all directions, the amount of their inclination diminishing in pro- 

 portion to their distance from it. We find, however, that the case 

 is precisely the reverse : as the beds approach the base of the cliff, 

 they dip towards it from every side at perpetually increasing angles, 

 until at the point of junction the inclination amounts in places to as 

 much as 55 degrees. The exact amount of dip in the various posi- 

 tions will be seen on referring to the accompanying map. 



VOL. IX. — NO. XCIV. 11 



