J. llofc — On Lithodomous Perforations. 5 



Wales. Mr, D. Mackintosh found thom in West Lancashire and in 

 Derbyshire, at ^oatly varyin<2; altitudes ; and iu tlie last November 

 number of the Geologioal Magazine they arc described by the Kov. 

 T. G. Bonney as found at the Ormeshoad. Thoy liavo also occa- 

 sionally been alluded to Ijy other writers as proofs of the elevation 

 of tlie coast in various places. 



The origin of these holes has been assigned to various agents, — to 

 atmospheric action or weathering — to the work of FholadcH before 

 the upheaval of the rock from the ocean — to snails — to a chemical 

 action combined with one of these, and to a mechanical action of 

 water or other abrading agent. Before, however, we consider which 

 is the most probable theory, it will be well more fully to describe 

 the holes and the situations in which they are found. They appear 

 to be confined to Limestone rocks, or, at least, they have only been 

 noticed in them hitherto, and with perhaps the exception of Monte 

 Pelegrino (the age of which I am unable to speak to with certainty), 

 to the upper Palceozoic rocks, and to the hard crystalline or semi- 

 crystalline strata in them ; and from the descriptions given by the 

 above observers, they appear to be similar in their position and in 

 their size, but those found by Mr. Pengelly are described as some- 

 what different in shape. I have personally had the opportunity of 

 examining only those found at Birkrigg, and therefore in my de- 

 scription will confine myself principally to them. 



In May last I was present at a meeting of the Geological Society, 

 when a paper on "Apparent Lithodomous Perforations," by Mr. 

 Mackintosh, was read, and I heard the discussion which followed ; 

 but having previously seen some specimens belonging to Miss 

 Hodgson, I must confess I was not satisfied with the conclusions 

 arrived at. 



On my return into Lancashire, I went to Ulverston, and having 

 called on Miss Hodgson, was guided by her to the locality in ques- 

 tion, which I found to be on Birkrigg Common, near the summit 

 of a hill of mountain Limestone, overlooking Morecambe Bay. The 

 situation of the rocks is shown on the six-inch scale Ordnance Map 

 of Lancashire, plate 16, about two and a half miles south of Ulver- 

 ston, and they are there called " Plat Limestone Eocks," and are, 

 where the specimen (Fig. 1) was found, about three hundred and fifty 

 feet above the sea. The common is crossed by several nearly parallel 

 outcrops of thin but hard beds of mountain Limestone, all dipping 

 slightly in the same direction, but parted by pasture several yards 

 wide, growing evidently on the partially denuded surface of the 

 intervening softer beds (rotten rock), and leaving the basset edges 

 of the harder beds exposed, and frequently slightly overhanging from 

 one to two feet above the pasture. These overhanging ledges form 

 a shelter from the prevailing winds, and the sheep feeding on the 

 pasture creep under them for protection, and by long and repeated 

 action the wool on their backs has piit a bright polish on the under 

 surface of the ledge, showing the power of prolonged friction on the 

 hard Limestone, even by so soft a substance as wool. 



The ideal section, Plate I, Fig. 4, will give a notion of this ar- 



