214 Sir C. Lyell, on the Changes of the Temple of Scr apis, 



of Ischia ; and to the exact agreement of these, as well as other fossil 

 shells, since collected by M. Philippi, with species now inhabiting 

 the Mediterranean. If the antiquity of such elevated deposits, when 

 contrasted with those found during the last 2000 years in the 

 neighbourhood of the Temple of Serapis, be as great as the relative 

 amount of movement in the two cases, or as 2000 is to 30 feet, it 

 would show how slowly the testaceous fauna of the Mediterranean 

 undergoes alteration : and therefore that naturalists ought not to 

 expect to detect any sensible variation in the marine fauna in the 

 course of a few centuries, or even several thousand years. 



In conclusion : the probable causes of the permanent upheaval 

 and subsidence of land were considered — the expansion of solid rocks 

 by heat, and their contraction when the temperature is lowered, the 

 shrinkage of clay when baked, the excess in the volume of melted 

 stone over the same materials when crystallized, or in a state of 

 consolidation ; and, lastly, the subterraneous intrusion of horizontal 

 dikes of lava, such as may have been injected beneath the surface, 

 when melted matter rose to the crater of Monte Nuovo, in 1538. 

 A large coloured section of a cliff, 1000 feet high, at Cape Giram, 

 in Madeira, was referred to as illustrating the intrusion both of 

 oblique and horizontal dikes, between layers of volcanic materials 

 previously accumulated above the level of the sea, and after 

 Madeira had been already clothed with a vegetation very similar to 

 that with which it is now covered. The intercalation of such 

 horizontal sheets of lava between alternating beds of older lava and 

 tuff would uplift the incumbent rocks, and form a permanent support 

 to them ; but when the fused mass cools and consolidates, a partial 

 failure of support and subsidence would ensue. 



[C. L.] 



