Report on the Moel Tryfaen Drift. 115 



shock or tremulous motion was felt by anyone, and the seismograph 

 at the Low-level Observatory at Fort William showed no sign of 

 any movement. The noise was heard also at Blarmacfoldach and 

 Lundavra, which are respectively 3 and 5 miles to the south 

 of Fort William ; all thi-ee places being close to the northern 

 boundary fault of the Highland district. As to the seismic origin of 

 the sound, there can be little doubt, for the district is one where 

 slight shocks are occasionally felt, and all the observers agree that it 

 was an ' earthquake-noise.' So far as our knowledge of the earth- 

 sound goes, its evidence confirms the conclusion that the great fault, 

 or one of the system of faults, hades to the south-east. 

 [To he continued in our next Number.) 



IV. — Eeport on the Drift at Moel Tryfaen.^ Drawn up by the 

 Secretary, E. Greenly, F.G.S. 



Introduction. — In August, 1898, it became known that what is 

 perhaps the clearest and most instructive section in the famous 

 high-level drift deposits at Moel Tryfaen must in a short time be 

 swept away in the course of the quarrying operations. There are 

 two slate quarries on Moel Tryfaen, the "Alexandra" and the 

 " Moel Tryfaen " Quarries, excavated in the same line of strike of 

 the slates. Gradually expanding, they had approached each other 

 so nearly as to leave a narrow bank between them with no more 

 than a yard or two of uncut turf upon it. Now the drift sections 











P\4 





"^ .jef 



Fig. 1. — Map of part of Moel Tryfaeu from Six-inch Ordnance Map. 



thus in danger of destruction are exceedingly important for the 

 following reasons : (1) They are at right angles to the strike of 

 the slates, and thus display the character of the underlying rock 



1 Report of the Committee, consisting of Dr. H. Hicks (Chairman), deceased, 

 Mr. E. Greenly (Secretary), Professor J. F. Blake, Trofessor P. Kendall, Mr. G.W. 

 Lamphigh, Mr. J. Lomas, Mr. T. Mellard lleade, Mr. W. Shone, and Mr. A. 

 Strahan, appointed to make photographic and other records of the disappearing di-ilt 

 section at Moel Tryfaen (spelt Tryfan in New Ordnance Survey Maps). Reprinted 

 from the British Association Report, 1899 (1900), pp. 414-423. 



