64 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



have contrived, in some measure at least, to follow the stages of 

 evolution through which the present condition of volcanic energy 

 over the surface of the earth has been reached. 



An investigation of this chronological nature must evidently 

 start from a definitely ascertained stratigraphical base. Until the 

 true order of succession of the rocks has been determined, it is im- 

 possible to make any satisfactory collation of the geological history 

 which they chronicle. In this country, thanks in large measure to the 

 labours of Fellows of our Society, the general stratigraj^hy has been 

 so carefully worked out that probably no part of the earth's surface, 

 of the same extent, has had its geological annals so well deciphered. 

 Moreover, it has been our good fortune here to find the geological 

 record marvellously complete. Undoubtedly we meet here and 

 there with blanks in the chronicle, which must be supplied from 

 elsewhere ; but there are probably few areas of corresponding size 

 on the face of the globe where such blanks are so few and unim- 

 portant. 



But not only is our general stratigraphical series remarkably full ; 

 it includes a succession of volcanic rocks of altogether unrivalled 

 continuity and variety. Placed on the edge of a continent and the 

 margin of a great ocean-basin, the site of Britain has lain along 

 that critical border-zone where volcanic energy is most active and 

 continuous. Its geological records have accordingly preserved the 

 memorials of volcanic eruptions from pre-Cambrian down to Older 

 Tertiary time. Some of these memorials have been studied in 

 minute detail, and with the general characters of the rest we are 

 more or less familiar. The time, however, seems now to have 

 come when an attempt may be made to present a general outline 

 of the whole volcanic history of the region. Such is the task on 

 which I have for some time been engaged, and the subject seems to 

 possess sufficient importance to be worthy of being laid before the 

 Society as the theme of the present Address. 



Without entering into detailed descriptions which would be out of 

 place on such an occasion as the present, I shall endeavour to por- 

 tray in broad outline what seem to me to have been the leading- 

 characteristics of volcanic action during each great geological period, 

 beginning with the most ancient records yet discovered. But so 

 full and varied are the volcanic chronicles of our area that even such 

 an outline, if it W3re to embrace the whole series of events, from the 

 earliest to the latest, would extend to so great a length as to task 

 the patience and endurance of even the most sympathetic listener. 



