Section C. — British Association. 463 



The time when they became extinct would doubtless amaze us by 

 its magnitude, if it could be stated in years, but yet it is compara- 

 tively so recent that not all the undying forces of atmospheric 

 degradation have heen able to obliterate their individual origin. 



It is, however, generally very different with respect to volcanoes 

 of Mesozoic age, for, though Lyell stated with doubt, that volcanic 

 products of Jurassic date are found in the Morea, and in the 

 Apennines ; and Medlicott and Blanford consider that probably 

 the igneous I'ocks of Eajmahal may be of that age, we must, perhaps, 

 wait for further information before the question ma^^ be considered 

 as finally settled. Of Jurassic age no actual craters remain. Darwin 

 also has stated, on good grounds, that in the Andes a line of volcanic 

 eruptions has been at work from before the deposition of the 

 Cretaceo-Oolitic formation down to the present day. 



In the British Islands we have a remarkable series of true volcanic 

 rocks, the chronology of which has been definitely determined. The 

 oldest of these belongs to the Lower Silurian epoch, as shown, for 

 example, on a large scale in Pembrokeshire, at Builth in Radnor- 

 shire, in the Longmynd country west of the Stiper stones in 

 Shropshire, and on a far greater scale in North Wales and Cumbria. 

 Of later date we find volcanic lavas and ashes in the Devonian 

 rocks of Devon, and in the Old Red Sandstone of Scotland. The 

 third series is plentiful among the Carboniferous rocks of Scotland, 

 and in a smaller way interstratified with the Coal-measures of South 

 Staffordshire, Warwickshire, and the Clee Hills. The fourth series 

 chronologically is associated with the Permian strata in Scotland, 

 and the fifth and last consists of the Miocene basaltic rocks of the 

 Inner Hebrides and the mainland of the West of Scotland. 



In the British Islands the art of geological surveying has, I 

 believe, been carried out in a more detailed manner than in any other 

 country in Europe, a matter which has been rendered comparatively 

 easy by the excellence of the Ordnance Survey Maps both on the 

 1-inch and the 6-inch scales. When the whole country has been 

 mapped geologically, little will remain to be done in geological 

 surveying, excepting corrections here and there, especially in the 

 earliest published maps of the South-west of England. Pala9onto- 

 logical detail may, however, be carried on to any extent, and much 

 remains to be done in microscopic petrology which now deservedly 

 occupies the attention of many skilled observers. 



Time will not permit me to do more than advert to the excellent 

 and well-known geological surveys now in action in India, Canada, 

 the United States, Australia, New Zealand, and South Africa. 



On the Continent of Europe there are National Greological Survej^s 

 of great and well-deserved repute, conducted by men of the highest 

 eminence in geological science ; and it is to be hoped the day may 

 come when a more detailed survey will follow the admirable map 

 executed by Sir Roderick Murchison, De Verneuil, and Count Key- 

 serling, and published in their joint work, " The Geology of Russia 

 in Europe and the Ural Mountains." 



It is difficult to deal with the Future of Geology. Probably in 



