Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/377

 Mr. Mackintosh believed that a minute study of the actual effects of rain and other atmospheric agents would convince any one that these perforations were not the result of weathering. " The pits, holes, or crevices produced by chemical decomposition, or the slight mechanical action of rain-drops *, are either rough or present no regularity of outline, and they always conform to the varying composition and structure of the rock. The distinction between the perforations under notice and all other indentations in limestone rocks is obvious." In one large specimen Mr. Mackintosh noticed that the perforations were more circular, smooth, and cleanly cut than a hole made by an iron borer, which happened to be in the same slab of rock. " They all present a uniformity of pattern irrespectively of the character of the rock. They generally occur in groups, which often ramify from a large shallow entrance or lobby. In most cases the mouths of the holes would appear to have been either fractured off by frost or in some other way destroyed ; but instances have been found in which they have been preserved, and then the mouths are seen to be smaller than the interior of the holes. They frequently exhibit circular striae, as if excavated by a rotating, or partially rotating, agency. The perforations have been ground out by some cause as evidently as any rock-surface has been subjected to a grinding process They are associated with smoothly hollowed, rounded, and funnelled rock-surfaces which run under the drifts of the limestone districts of North-west Lancashire."

In conclusion, the author expressed his belief that the holes were ground out by some animal while the land was submerged, either before, during, or after the Glacial period.

P.S. Very lately (July 1869) I have found numerous similar perforations at altitudes between 1000 and 1400 feet above the sea, near Buxton, the most perfectly preserved (about seven-eighths of an inch in diameter, and often 3-1/2 inches long) occurring on the steep or south-west side of Hill-head Valley, about a mile S.E. of Parks Inn.— D. M.

Discussion.

Mr. Gwyn Jeffreys remarked that Mr. A. Tylor had already called attention to the same subject three years ago. He could not agree in regarding the perforations as made by any mollusk or other animal. The borings of Pholas, Saxicava, and Gastrochoena were not parallel, but enlarged towards the base into a pear-shaped form. They were also comparatively straight, and not curved or bifurcated as in the limestones exhibited. The range in height was also against their being the work of marine mollusks. He thought the perforations were more probably due to atmospheric agency.

Prof. Ansted had seen in the large blocks of the Cyclopean walls of

sides of projecting ledges or blocks, in situations to which rain has little or no access."
 * " The holes generally open downwards, or horizontally, on the protected