PROCEEDINGS OF THE COTTESWOLD CLUB 259 



and the Hebrides, where sheets of basah 3,000 feet thick 

 have been spread over the whole district during the 

 Miocene period, sections of which are seen in Fingal's 

 Cave, the Scuir of Eigg, and oven so far off as tho Giant's 

 Causeway. 



A closer parallel may be found in the district of 

 Auvergne, where large basaltic plateaux occur, pierced 

 through by masses of eruptive trachyte such as the Pic de 

 Sancy and the well-known Puy de Dome. The date of 

 the outburst in Central France was probably nearlv the 

 same as that of one, at any rate, of the periods of volcanic 

 disturbance in the Rocky Mountains, viz., the commence- 

 ment of the Tertiary ])eriod ; but in the Yellowstone 

 district there have been at least two epochs of intense 

 activity, the earlier flooding the region with sheets of 

 andesitic lavas, the later characterised by lavas of the 

 basaltic type. These latter seem to belong to the Pliocene 

 period, but considerable erujnions must have taken place 

 in still later times, and the existing thermal phenomena 

 are the last expiring efforts of these volcanic energies ; if 

 indeed they are dying out, and not gathering strength for 

 a fresh out-burst. 



The latest period of activity, however, took place so long 

 ago that not a single crater corresponding to the splendid 

 row of symmetrical cones which astonish the traveller in 

 Auvergne, has survived the destructive action of weather 

 and water. Probably most of the lava issued from long 

 narrow fissures, as in the case of the Pic de Sancy and the 

 hills in the Cantal district. Glacial action and river 

 erosion have ploughed out valleys in the basaltic plateaux 

 until the original volcanic contours of the region are no 

 more recognisable than the features of the vouth can be 

 traced in the wrinkled old man. 



Many interesting evidences of the work of ice are 

 observable ; rocks polished and striated in the caiions, 

 mounds of moraine in the valleys, and blocs pcrchds of 



