1856.] MOORE SILURIAN ROCXS OF WIGTOWNSHIRE. 363 



no exception to the rule that the axis of the curves bends to the 

 north. 



If, now, we cross over to the east side of the Bay of Luce, we shall 

 find confirmations of the same structure. From Port William to the 

 Burrow Head, the rock is seen to dip north ; then it is perpendi- 

 cular ; and after three magnificent undulations, of which the northern 

 sides are the longest, it plunges perpendicularly into the sea. 



Returning to Port William, which is about the parallel of the 

 Grennan Rocks, where the change of dip is seen on the western 

 side of the bay, we find that here also as we go north the dip is 

 reversed ; and from thence to Glen Luce, the rock is either vertical 

 or dips south. From thence to the Cairn, the section, being inland, 

 is too much concealed to give any results ; and I would remark that 

 all these observations are drawn solely from coast-sections ; as in 

 those only where the base is washed by the sea can the rocks be 

 followed uninterruptedly for any distance. Whenever we leave the 

 coast, the rock, particularly when inclined at low angles, is so covered 

 by drift that no conclusions can be arrived at. Omitting therefore 

 everything until we reach the Cairn (fig. 3), we there find the slates 

 vertical ; about a quarter of a mile to the north they are seen dipping 

 south at an angle of about 30° ; from thence to Glen App they are bent 

 into three or four sharp folds, always dipping south ; on the north 

 side of Glen App they are seen for the last time highly inclined, but 

 still with a south dip ; and from thence set in a series of flaggy beds 

 which also dip south, or are vertical, until we reach the coarse con- 

 glomerate, with blocks of granite and porphyry, which is the conti- 

 nuation of the beds of conglomerate at Corswall Point, from which 

 we set out. The beds cannot be pursued much farther, since at the 

 Correrie Burn the rock changes its character ; and from thence to the 

 Stinchar consists solely of porphyry, greenstone, and amygdaloid. 



The structure I have described is similar to those inversions of 

 rock in the north of Germany, in the Ardennes, and the Eifel, and 

 to that of the Appalachian chain in the United States. It has never 

 yet been observed in this country on so considerable a scale ; and 

 what is very remarkable, if my view be correct, it does not obtain in 

 the parts of the chain to the eastward. There, according to the 

 published sections of Prof. Harkness, Prof. Nicol, and Sir Roderick 

 Murchison, the lowest rocks form an anticlinal of the normal cha- 

 racter, with the newer beds on their flanks dipping away from the 

 older : whereas in Wigtownshire, as I shall presently show, these 

 Graptolitic schists in the centre of the section are older than the con- 

 glomerate to the north, on which they appear to repose. It is also 

 observable, that where the change in the dip of the axes of the curves 

 takes place, there is no such change of circumstances as to hint at 

 the cause. In the parallel cases quoted above there is always present 

 some great mass of granite, gneiss, or crystalline schist, which appears 

 by its forcible intrusion to have occasioned the inversion of the masses 

 on its flank. Here nothing of the kind is observable : the hills pre- 

 serve the same heights with little variation : there is no unusual ap- 



VOL. XII. PART I. 2 C 



