On the Geology of the Tonga Islands. 229 



The visible sections are only those given, at hand by ditches, and 

 at a considerable distance north and south by pits at Bury St. 

 Edmunds and Sudbury. The appearances in these harmonize with 

 that conclusion. Conclusion and appearances differ from what we 

 should expect on the theory that this Boulder- clay was the product 

 of the attrition between an ice-sheet and its bed. 



2. " On the Melaphyres of Caradoc, with Notes on the Associated 

 Felsites." By Prank Kutley, Esq., E.G.S. 



Within very limited areas the melaphyres of Caradoc differ con- 

 siderably in texture and in structure, some having once been 

 basalt-glass or andesite-glass (such being the superficial portions of 

 a lava-stream) ; others have possessed a certain amount of inter- 

 stitial glass, which has subsequently been rendered more or less 

 opaque by the development of magnetite, while at times it appears 

 to have been converted into a palagonitic substance. In some 

 of the rocks the crystalline texture is very fine, in others com- 

 paratively coarse. Near the summit of Caradoc is a basalt-tuff or 

 andesite-tuff. 



The melaphyre or dolerite of Little Caradoc differs from the lavas 

 in that the augite remains fresh and the felspars are altered, while 

 in the lavas of Caradoc proper the pyroxenic constituent is decom- 

 posed and the felspars remain as a rule unaltered. 



Whether the melaphyre of Little Caradoc may be regarded as a 

 neck from which the lavas lying to the south-west of it emanated, 

 is a point which can only be demonstrated by further field-work. 



The author considers that further investigation may prove beyond 

 dispute that the associated felsites are rhyolites of which the original 

 structures have as a rule been almost entirely obliterated. In an 

 appendix further evidence is adduced in favour of the original rhyo- 

 litic nature of these felsites, and a fragmental rock from Bowdler's 

 Chair is described as unquestionably a rhyolite-tuff. 



3. " Notes on the Geology of the Tonga Islands." By J. J. 

 Lister, Esq., M.A. 



The islands of the Tonga group are situated on a long ridge which 

 rises from deep water on either side to within a thousand fathoms of 

 the surface of the sea. The general direction of the ridge is N.N.E. 

 and S.S.W. 



(1) A line of volcanoes, some active, some extinct, traverses the 

 group. Continued southward, the direction of the line passes through 

 the volcanoes of the Kermadec group, and those of the Taupo zone of 

 New Zealand ; while to the north it cuts the line of the Samoan 

 volcanoes at right angles. 



(2) Besides the purely volcanic islands there are some formed by 

 submarine eruptions, whose layers have been laid out under water 

 and since elevated, with or without a covering of limestone. 



(3) The remaining islands are formed entirely of limestone. 

 Eua is an example of the second group. The volcanic basis con- 

 sists for the most part of beds laid out beneath the sea, and some of 



