446 Lomas : Geology at the British Association. 



was discussed by Dr. H. H. Bemrose, in a paper which dealt 

 very fully with their petrographical characters. Numerous 

 photographs were thrown on the screen, illustrating the struc- 

 tures found in the Mountain Limestone, Metamorphic Lime- 

 stones, and Metasomatic varieties. Of special interest were 

 series showing the gradual transitions from a pure limestone, 

 through limestone with quartz crystals, quartzose limestone, 

 to quartz rock, and others exhibiting changes from pure lime- 

 stones to dolomites and quartzose dolomites. 



Mr. H. Brodrick described the occurrence of Cave Pearls 

 in certain limestone caves in Derbyshire and Ireland, and also 

 announced the discovery of Reptilian footprints from the 

 Oolitic rocks near Whitby. 



Professor W. M. Davis traced the steps by which Snowdonia 

 has assumed its present form, and suggested that the occurrence 

 of cwms, blunted spurs and over-deepened valleys were, in 

 large measure, due to glacial erosion. 



Dr. Tempest Anderson exhibited a beautiful series of photo- 

 graphs, showing the changes in the Soufriere of St. Vincent 

 since the great eruption of 1902. 



Perhaps the culminating point of interest was reached 

 during the discussion on Mountain Building. The President 

 opened the proceedings by enunciating a new theory of liquid 

 or viscous horsts. He showed that rocks in a deep synclinal 

 fold must exist in this condition, and the effects of recumbent 

 folds could well be produced by great forces acting on liquid 

 masses existing below the surfaces. 



Sir Archibald Giekie, following the President, referred to 

 the two main types of mountain structure ; chains like the Alps, 

 which are plications of the terrestrial crust, and upraised 

 plateaus having an approximately horizontal arrangement of 

 their constituent rocks. 



On general principles, he stated that we were still wanting 

 means of deciding whether phcations were rapid or slow, or 

 whether they were still going on. He suggested that dehcate 

 geodetic observations might settle these questions. 



Prof. C. Lapworth gave a general resume of Earth folding 

 as a whole, and dealt specially with the harmonic relationships 

 which mountain chains exhibit. 



Prof. W. J. SoUas referred to the work of Prof. Lugeon in 

 the Swiss pre- Alps as affording support to the President's 

 theory, and showed that viscous material might be transferred 



Naturalist, 



