Geology. 



129 



Sir Charles then alluded to his discovery, in 1828, of marine shells in 

 volcanic tuff, at the height of nearly 2000 feet, in the island 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 neighborhood 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 the 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 shrink- 

 age 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 colored 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 vol- 

 canic 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 up- 

 lift 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. 



8. A Geological Reconnoissance of the State of Tennessee, being the 

 Author's first Biennial Report, presented to the thirty-first General Assem- 

 bly of Tennessee, December, 1855; by James Safford, A.M., State 

 Geologist, Professor of Natural Science in Cumberland University, Leba- 

 non, Tennessee. 164 pp. With a colored Geological map of the State. 

 Nashville, Tenn., 1856. — Prof. Safford is contributing much to our knowl- 

 edge of the geology of Tennessee and its mineral resources. This bien- 

 nial report is occupied mainly with the latter, taking up in order the 

 ores of iron, copper, lead and zinc, gold, coal, marble, greensand, hydraulic 

 limestone, etc. The last 40 pages are devoted to the geological structure 

 of the State, under which the foldings, dislocations, and denudation of 

 the rocks are briefly discussed, and the order and character of the rocks 

 explained. We cite the following from pages 148, 149 and beyond. 



upheaval above mentioned, Mr. Roberts states, that settlers have now to go three 

 miles farther up the river Wairau to obtain supplies of fresh water, than they did 

 before the earthquake of January, 1855. There was no volcanic eruption in the 

 northern island at the time of these events ; but the natives allege that the tem- 

 perature of the Taupo hot-springs was sensibly elevated just before the catastrophe. 



During a previous earthquake in 1832, other alterations in the relative level of 

 land and sea occurred ; and many of the colonists fear a repetition of such move- 

 ments every seven years, for in 1848 there were violent convulsions. The larger 

 part, however, of New Zealand has not suffered any injury during the same period 

 from earthquakes. 



SECOND SERIES, VOL. XXII, NO. 64. — JULY, 1856. 17 



