Yol. 69.] VOLCANIC ROCKS OP THE EOEEAKSHIKE COAST. 469 



of the calcite-ruatrix over patches measuring a quarter to half an 

 inch in diameter. The heach is covered with large boulders set 

 close together, but its foundation appears to consist of volcanic 

 rock, and some large stacks of basalt in situ stand out at low-water 

 mark between these masses of sandstone and the sea. Some 

 50 yards farther north-east, an escarpment 150 yards long may be 

 seen at exceptionally low tide. Its edge is almost horizontal, and 

 strikes north-west and south-east. The rock consists of a* well- 

 bedded sandstone-breccia, dips north-eastwards at about 5°, and 

 appears to rest upon a denuded surface of volcanic rock. 



The close lithological resemblance between these sandstones and 

 the Upper Old Red Sandstone of Boddin Point, coupled with (as 

 Dr. Hickling informs me) their dissimilarity to any of the sand- 

 stones of the Cairnconnan Series, favours the opinion that they 

 are of Upper Old Red Sandstone age, a probability which is 

 strengthened by the marked unconformity that appears to exist 

 between them and the lavas upon which they rest. 



Further, it seems very likely that the mass of Upper Old Red 

 Sandstone, which rises a little above high- water mark at Boddin, 

 skirts the coast not far below low-water mark from Fishtown of 

 Usan to the Lunan- Water estuary, being thrown down by the 

 faults that run parallel to the coastline ; also, that it continues 

 under Lunan Bay and much of the drift-covered area on the west, 

 reappearing in the cliff and along the shore south of Lunan Bay 

 in close relation with another series of faults, which are cognate 

 with those on the north side of the bay, and have a similar effect in 

 determining the line of cliffs. It is significant that such an area of 

 Upper Old Red Sandstone coincides remarkably in position with 

 the Upper Old Red Sandstone which emerges here and there through 

 the superficial deposits north of Montrose, and is possibly continuous 

 beneath them. The same kind of feature is again repeated in the 

 occurrence of Upper Old Red Sandstone at Seaton Bay, north-east 

 of Arbroath. 



An attempt has been made to represent, by means of the accom- 

 panying ideal section (fig. 5, p. 470), every important feature along 

 the coast from the south-western corner of Lunan Bay to the Red 

 Head. The rocks are so admirably exposed, that most of what is 

 set down may be directly observed, little being the product of 

 mere inference. This is more particularly the case with the part 

 of the coastline trending from north to south outside Lunan Bay. 



From what has already been said, it will be understood that 

 the base of the series of lavas south of Lunan Bay is not exposed. 

 How far they extend northwards under the cover of Upper Old Red 

 Sandstone is merely a matter of conjecture. Inland they thin out, 

 as represented on the Geological Survey map, towards the south- 

 west. It is probable that they thicken north-eastwards, and ulti- 

 mately unite with the lavas north of Lunan Bay, the intervening 

 Cairnconnan Sandstones thinning out in the same direction. 



The lavas succeed each other regularly, with the usual admixture 

 of sediment in the upper portion of each sheet, until at Ethie Haven, 



