334 Correspondence — A. Strahan. 



shales and mudstones, but contain a group of volcanic tuffs on the 

 horizon of the pisolitic ironstone. 



The Carboniferous rocks appear to be about 700 feet thick, and 

 contain conglomerates, sandstones, and shales, with plant-remains 

 about the middle of the series. 



The glacial strias sweep round from SSW. at the north, to S.W. 

 and WSW. at the south end of the district. In the Penmon area 

 there is cross-hatching with a series running SSE., and it is 

 suggested that this is due to fluctuations in the power of the Car- 

 narvonshire glaciers to deflect the ice coming from the north, 

 combined with the local influence of certain high ground. 



3. " Seismic Phenomena in the British Empire." By M. F. 

 de Montessus de Ballore, Captain of Fortress Artillery at Belle-Ile- 

 en-Mer. (Translated by L. L. Belinfante, B.Sc, B. es L. Com- 

 municated by Sir Archibald Geikie, D.Sc, F.R S.) 



The author gives a brief outline of a plan that he has elaborated 

 for studying Seismology. He has separated his work into four 

 parts — I. The. formation of an Earthquake Catalogue. 2. Refuta- 

 tion of the empirical laws previously enunciated. 3. Description of 

 the globe from a seismological point of view. 4. Investigation of 

 the characters which differentiate stable from unstable regions. 



He gives a method by which the relative seismicity (or instability 

 as regards earthquakes) of regions may be obtained and registered, 

 and indicates some of the results which he has derived from his study, 

 including the intimate relationship between instability and surface- 

 relief, and the independence of seismic and volcanic phenomena. 



The main part of the paper is a section of the third division of 

 the author's work, and deals in detail with the earthquakes of the 

 British Empire. In this part of the paper, the recorded earth- 

 quakes of the British Isles, India, Australia and New Zealand, 

 British Africa, Canada, and various scattered possessions are 

 described. 



COKEESPOUDEIsrCE. 



EOCENE BEDS AT BINCOMBE, DOESET. 



g IK; — l n your last issue (p. 247) Mr. Fisher says that if I had 

 seen the section of Eocene beds at Bincombe open as he did, 

 I might not have been at a loss to find room for the full thickness 

 of chalk below them. But though I did not see the section, I had 

 seen what was next best to it, and that was Mr. Fisher's account of 

 it, showing the Eocene to be vertical. The chalk also is almost 

 certainly vertical, or nearly so, between the Eocene and the mouth of 

 the tunnel, where we are close to its base, but even so I was not 

 able to pack in its full thickness, and had therefore to assume an 

 overlap by the Eocene. 



Mr. Fisher explains the occurrence of the Eocene gravels on the 

 theory that they are wedged into the chalk by two faults, and do 

 not occur as an outlier in the usual sense of the word. This 



