216 On the Vents of Hot Vapor in Tuscany. 
tion of the chief ridges of Italy is more or less at right angles to 
the main direction of the Alps, we know that the greatest amount 
of metamorphism has been impressed on both chains after the 
nummulitic period ; and again, that in both, very violent move- 
ments took place after the deposition of the miocene tertiary. In 
he chief range of the Swiss and Austrian Alps, the greatest 
changes of metamorphism, elevation, depression, and contortion 
n 
linear bands trending generally from N.W. to S.E., and even 
veering round to a meridian strike as they approach the direc- 
tion of the anciént and paleozoic rocks of Corsica and Sardinia. 
Notwithstanding, however, their great diversity of direction, the 
Alpine and the Sardinian lines of active disturbance have eac 
been manifested along primeval coasts, the strata formed upon 
which contain paleozoic fossils. When, however, we pass from 
the consideration of events so long past to the contemplation of those 
agents of terrestrial change which have been most active in compat- 
atively recent times, the Appennines are at once distinguished from 
the Alps in possessing those truly voleanic phenomena which con- 
nect geology and existing history. With the most frequent evr 
dences of recent mutations to an enormous extent in their outlines 
—1. e. since the period of the glacial waters*—the Alps present no- 
where the trace of any subaérial voleano ; the youngest igneous 
rocks being those which have traversed the older tertiary deposits 
of the Vicentin and other tracts. The Appennines, on the eon- 
trary, offer proofs, particularly on their western shores, not only of 
recent oscillations, but also of copious voleanic eruptions. Thus, 
early Greek settlements in the Bay of Naples. _ 
Lastly, let us recollect, that in the tract of Western Tuscany, 
which has beer the special subject of this memoir, we also 
a most instructive lesson upon the efforts of subterranean igneous 
JSorces to develop themselves at successive periods along one ane 
the same established band of active change in the crust of the 
—_—— 
* See “ Distribution of the Superficial Detritus of the Alps, compared with that 
of Northern Europe.” (Quart. Jour. Geol. Soc., vol. vi, p. 65.) 
t Quart. Jour. Geol. Soc., vol. vi, p. 294, 
