Vol. 57.] MESOZOIC ROCKS IN THE ISLAND OF ARRAN. 243 



basin of the Clyde. Since that time the whole of the existing 

 topography has been carved out. So vast has been the denudation, 

 that the Chalk and the Lias have been entirely stripped oif the 

 country, as they have been likewise in Antrim, save where protected 

 by the overlying basalt-plateau ; while the much thicker Triassic 

 sandstones and marls have been reduced in area to what is seen 

 of them in Arran, and what may still lie concealed under the Eirth 

 of Clyde. 



The island of Arran has long been famous for the variety of its 

 geological structure, but the recent detailed work of the speaker's 

 colleagues of the Geological Survey has shown this variety to be far 

 more wonderful than had ever before been imagined. In particular,, 

 its volcanic history has been found by l^Ir. Grunn to be especially full, 

 from the time of the presumably Arenig rocks, on through the Lower 

 Old Red Sandstone and the Carboniferous Series, to the complex 

 assemblage of Tertiary masses. The geological survey of the island is 

 now completed, and has had a most appropriate consummation in the 

 discovery described in the present paper. Sir Archibald was sure 

 that the Fellows would agree with him in thinking that Mr. Peach 

 and Mr. Gunn were to be congratulated upon the skill' and insight 

 with which they had worked out a piece of difficult ground'; that 

 Mr. Macconochie deserved hearty thanks for the intelligence and 

 enthusiasm which had led to the discovery of the fossiliferous masses 

 in the vent ; and that to no fitter hands than those of Mr. Newton 

 could the fossils have been entrusted, which have revealed the 

 former presence of so many Mesozoic horizons in the South of. 

 Scotland. 



