INEQUALITIES OF UPRISE 319 



present solitude, and in that event, the geologists 

 of Rome will no doubt be on the watch for all the 

 information that can be gathered from this source 

 as to the nature of the rocks underneath, and their 

 relations to each other. 



In the meantime, much might be done in this 

 attractive department of local geology by a far more 

 detailed study than has yet been attempted of the 

 surroundings of the Campagna. In particular the 

 recognisable stratigraphical horizons among the Plio- 

 cene strata should be definitely traced and mapped 

 in detail, where they emerge from under the volcanic 

 tuff. It would then be possible to measure the 

 amount of erosion in various places, and to deter- 

 mine how far the spread of the volcanic sheet across 

 older formations is due to actual unconformability 

 and how far to simple overlap. At the same time, 

 the precise height could be ascertained of the upper 

 limit of the Pliocene deposits, and data would probably 

 be obtained for determining not only the minimum 

 amount of the uplift of the land since the Pliocene 

 period, but also how far and in what directions there 

 may have been any warping of the peninsula in the 

 course of the elevation. We know from the obser- 

 vations of De Angelis that the Plaisancian clays, 

 which at Monte Mario do not rise more than 

 200 feet above the surface of the Mediterranean, reach 

 a height of as much as 1,050 metres (3,445 feet) in 

 the upper part of the valley of the Arno, near Subiaco, 

 only about thirty miles east from Rome, or an up- 

 heaval of as much as 108 feet in a mile. It 

 remains still to discover how far this amount may 



