Correspondence — Mr. Dugald Bell. 189 



they are of Old Red Sandstone age. It is the object of the author 

 to show the correctness of the latter supposition, and he brings 

 forward evidence to prove that the red rocks rest unconforniably 

 upon the Lower Palasozoic rocks, or are faulted against them, and 

 that the breccias of the red rocks contain fragments of the Lower 

 Paleeozoic rocks, and also of intrusive rocks which break through 

 the latter. The red rocks also resemble deposits which are known 

 to be of Old Red Sandstone age. 



The Old Red Sandstone rocks of the district form an irregular 

 and incomplete elliptical ring around a denuded plateau of older 

 rocks. The incompleteness is due to the concealment of the southern 

 part of the ring beneath the sea ; but if the southern part of tliis 

 ring be as irregular as the northern portion, faulted patches of the 

 Old Red Sandstone rocks va^y well come in among the older rocks of 

 the cliffs in the positions where the beds which are discussed in this 

 paper occur. 



3. " On the Depth of the Source of Lava." By J. Logan Lobley, 

 Esq., F.Gl.S. 



The author contends that lava cannot have been brought to the 

 surface from a depth of 30 miles, as fissures which would serve 

 as conduits could not exist at that depth, and, moreover, the lava 

 would be consolidated before it reached the surface, owing to 

 contact with cool rook for a considerable period. He argues that 

 the pressure of the overlying rocks would cause the rocks even at 

 a depth of 10 miles to be practically plastic, as shown by M. Tresca's 

 experiments, and that no continuous fissure could occur in such 

 rocks. Estimates of the volumes of ascending lava-col iimns were 

 given, with a diagram comparing them with a 30-mile thickness of 

 rocks. 



THE HIGH-LEVEL SHELLY CLAYS AND MR. MELLARD READE.' 

 Sir, — My "writings on the subject" are not so "numerous" 

 by a long way as those of Mr. Mellard Reade, but I had hoped 

 that they were at least tolerably clear as far as they went. I 

 find, however, that my friend Mr. Reade has " completely misunder- 

 stood their tenour." He thinks I have made "strenuous endeavours 

 to prove that high-level shelly beds do not exist." This would 

 indeed be a waste of time on my part, in all cases where they 

 were ordinarily well attested. No ; freely admitting them in all 

 such cases, the point of interest with me has been — How were 

 they formed or deposited ? . Are they in situ, and do they indicate 

 former levels of the sea? Mr, Reade seems to hold as a matter 

 of course that they are and do ; and he even suggests that if 

 such shelly clays are found in one place, say at 1000 feet, it becomes 

 "futile " and a " waste of time " to question whether a different bed 

 (from all description) is found in another place at 500 feet ! On 

 the contrary, I hold that as some of these clays are known to 

 1 Geol. Mag., March, 1897. 



