Origin of the Rock-salt Formation. 195 
the limestone, marl, and gypsum; and in regard to this fact, 
nothing more is requisite than to ascertain more exactly the 
relative ages of these formations. 
** But if Von P. assumes that this sulphur is the cause of the 
existence and duration of the volcanos of Italy, we are by no 
means disposed to adopt his view ; although he has very clearly 
shown that the three active volcanos of Italy, (Vesuvius, Strom- 
boli, and tna); and moreover, the points which, according to 
history, have had only one vent (Ischia and the Monte-nuovo 
at Pozzuoli); and finally, those places of the Roman territory 
which display in the character of their mountains, traces of 
lava, and other effects of fire, as Valentano, Viterbo, Frescati, 
and perhaps Monte Rossi,—lie collectively in a floetz district 
which he has indicated (part of it lying at Solfaterra), and 
which contain sulphur and other inflammable substances. It 
is certainly not denied that in this tract a chemical agency 
displays itself in various ways; but it still seems to us very 
different from the proper volcanic agency. We dare not as- 
sume with Von P, that the former can rise to the height or 
vehemence of the latter. If it also is the fact that we cannot 
always distinguish on the surface of the earth, effects whose 
causes are deeply hid in the bowels of our planet, from those 
which are peculiar to the newer formations of the earth’s crust; 
and if, moreover, the earlier results of the chemical agency still 
operate in some places, it would be impossible to pass from 
the one class to the other, on account of the similarity between 
the weaker volcanic effects and the most striking phenomena, 
which are both produced on the surface of the earth by the 
same chemical process. 
** Was then the coincidence of the locality of the Italian vol- 
canos with the existence of the sulphuriferous tract merely 
accidental? That is a question which one might not answer ex- 
actly with a negative. Although the rationale of the association 
of those phzenomena is not quite clearly before us, and we can 
only premise obscurely, only hint at what it is; still it is not 
impossible that time may completely prove it to us. Perhaps 
too what Von P. regards as a cause of volcanic powers, may 
be only an effect of them? Such a hypothesis can be viewed 
only as a geological heresy, since the illustrious L. de Buch 
has given a very credible explanation of former volcanic agency 
to so wide an extent. The proportionately limited presence 
of gypsum of all forms, and its accompaniments of rock-salt and 
sulphur in the various formations of limestone, had long ago 
been observed, and may indicate that the formation is in a state 
of decline. With a view to this question we venture to draw 
attention, particularly, to the interesting letter of L. de B. to 
M. Freisleben, concerning the Hartz. 
2B2 “ The 
