282 Reports and Proceedings. 



causes pointed out by the author. He did not, however, regard them as entirely re- 

 sulting from subaerial denudation acting on a surface of uniform quality. There was 

 probably a difference in the proportions of the constituent parts in the granite, some 

 parts in the same quarry being soft, while others were of extreme hardness. These 

 softer parts were easily remoYed, while the harder parts were left. The question was, 

 whether this difference was the result of the original deposition or of subsequent se- 

 gregation. Even where china clay resulted from the decomposition of the rock, some 

 of the nodules of hai-der granite occurred. 



Prof. Brayley had observed similar spheroidal structure in other crystalline rocks, 

 and had called attention to the subject some years ago. The phenomena at Karn Bre 

 in Cornwall were much the same as on Dartmoor, and resulted from the concealed 

 concentric spheroidal sti-uchire of the rock, or what he might term spheroidal ten- 

 sion. In Leicestershire syenite, Rowley Rag, and Northumberland basalt the same 

 was to be ti-aced. He regarded it as the result of slow cooling. 



Mr. Scott had observed similar tors in the neighbourhood of Dublin ; and on ex- 

 amination of smaller blocks, each was found to contain a nucleus coated with a sort 

 of crust, formed principally of black Mica. In the stratified granites of Donegal 

 such nuclei did not occur. 



2. "I^otes on apparent Lithodonms perforations on the Hills of 

 I^orth-west Lancashire." By D. Mackintosh, Esq., F.G.S. 



The author described certain perforations discovered by him in the 

 limestone rocks near Morecambe Bay at altitudes varying from 200 or 

 300 to 667 feet above the sea. He stated that the course of these per- 

 forations seemed to be irrespective of any differences in the hardness of 

 the rock, and hence, and from the regularity and smoothness of the 

 cavities, he argued that they could not be the result of the chemical 

 and mechanical action of the atmospheric moisture. The perforations 

 were said to occur chiefly in groups, often ramifying from a common 

 entrance, and where the actual entrance is preserved this is narrower 

 than the more deeply seated portions. The author maintained that the 

 hollows described by him had been ground out of the rock, and he ex- 

 pressed his belief that they were made by some animal when 'the 

 land was submerged to the extent indicated by the altitutes at which 

 they occur.' Prom their position he supposed their formation to have 

 taken place during, or immediately before, the Glacial epoch. 



Discussion. — Mr. J. 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 

 marking as lithodomus borings. The borings of Saxicava and GastroclwEna 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 theii- being the work of marine mollusks. He 

 thought the holes were more probably due to atmospheric agency. 



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

 of various sizes, bored to different depths by the combined action of vegetation and 

 atmospheric influences. In some cases these holes were large enough to receive the 

 arm, and were two or three feet in length. 



3. " On the Parallel Eoads of Glen Eoy." By Prof. James Kicol, 

 P.R.S., P.G.S. 



The author briefly noticed the two principal hypotheses which have 

 been advanced to account for the formation of these terraces, and 

 asserted his own belief in their marine origin. He rested his argument 

 against the hypothesis of their lacustrine origin chiefly on the ground 

 that if their formation be due to successive periods of repose, alternating 

 with sudden drainings of a lake occupying the present valley of Glen 

 Hoy, we ought still to find traces of the violent debacles occasioned by 

 these drainings, or of large rivers in the gorges through which the 



