./. Rofe — On Lithodomous Perforations. 7 



aro in hard roclc, in wliich mctamorpliism has obliterated almost 

 every trace of oi'ganism : oven when fossils aro found, tlio holes 

 are sometimes bored through thoin, or partly through them, and 

 partly through the rock. Miss Hodgson, to whoso paper I. have 

 alluded, has a specimen in which the hole is bored partly through 

 a Oijatlwphjlliim longitudinally, and partly through the Limestone, 

 which appears to be softer than the coral, as the holo is rather flatter 

 on the side jDassing through the coral, showing that the worker 

 inclined to the softer material. I believe generally, but certainly in 

 the mountain Limestone of Lancashire, in every case where there 

 are fossils, they are not acted upon by the weather so easily as is 

 the rock in which they are imbedded, and therefore would not be 

 likely to decay and fall out of their beds and leave holes ; but, on 

 the contrary, the limestone weathers away from them, and in many 

 cases leaves the fossils beautifully clean, well displayed, and project- 

 ing from stone, as must be familiar to any observant person on the 

 roughly built boundary walls in any fossiliferous Mountain Lime- 

 stone district. In all these cases, rain or other water has free 

 access to them, first to disintegrate the matrix, and then to wash 

 away the debris. 



The action of rain, or of the carbonic acid contained in rain-water, 

 on limestone, is well known, and the effects of this weathering is 

 perhaps as well shown at Birkrigg as anywhere, but it is on the 

 surface of the rocks which are exposed to this action that we find 

 the effects, and not on the sheltered portion ; and as the exposed 

 rocks vary in hardness, probably from metamorphosed fossils con- 

 tained in them, the stones take many fantastic shapes, and are 

 collected for artificial rockeries. But to return to the borings, the 

 interior surface of these is smooth, except some very slight circular 

 marking round the cell, suggestive of a grinding action ; and that 

 this action is quite recent is shown by the state of some of the holes, 

 the lower portion, or that nearest the opening, being tinged slightly 

 green by a microscopic vegetation, whilst the upper or last ex- 

 cavated portion is perfectly fresh and white, having a fine granular 

 appearance very similar to what is given by washing the limestone 

 with dilute acid and allowing it to dry. This variation in the 

 appearance of the surface of the chambers has been noticed both 

 by M. Bouchard and by Mr. Bonney. The action of the atmosphere, 

 however, leaves a roughness and a quasi-columnar appearance, which 

 at once distinguishes it from the surface of the borings, as is very 

 evident when a boring has been fractured at the edge of the rock, 

 and the section of it exposed to the action of rain, some cases of 

 which occur on the edges of Fig. 1, where the effect of weather is 

 strongly marked. 



The next supposition is that they are the holes of Fholades, 

 excavated before the elevation of the rock above the sea, and thus 

 may be used as a proof and measure of such elevation ; and this in 

 reality is the principal geological interest connected with these 

 holes. Against this theory Birkrigg is a strong case, for the 

 burrows are in the underside of a nearly level rock, and bored 



