136 On a saline Substance'from Mount Vesuvius. 
demonstrated, as I have already had oceasion to mention, by the 
immense quantity of marine exuvie inclosed in the secondary 
strata. Now this character is found in the same countries as the 
volcanic eminences that are now the object, which I have parti- 
cularly described, along the left bank of the Rhine, between 
Coblentz and Bonn, and in the country of Hessia. These emi- 
nences have all the characters of the actual volcanoes, and in 
particular of Vesuvius. In them and around them are seen not 
only lavas of different degrees of porosity and of mere scori@, 
which successively flowed over each other, but between them 
layers of cinders and an immense quantity of pumice- stones. 
The pumice-stones are a known circumstence belonging to 
Vesuvius, but with a very remarkable character. It is not an 
ejection from the crater, or from any known part of that voleano 5 
it rises from the bottom of ihe sea, in parts where the water is 
very hot. My brother had the opportunity of discovering that 
circumstance by a dog, who was fond of swimming by the side of 
his boat, and sometimes cried out as being scorched by the 
heat ; and my brother actually found the water hot by plunging his 
hand into it. These are probably the places whence the pumice- 
slones come up from the bottom of the sea: they are found float- 
ing on the surface of the sea, as pumice-stone is specifically 
lighter than salt waéer. 
Now this very important and known volcanic product is found 
around some volcanic eminences near the Rhine. I have seen 
very extensive beds of pumice-stones on the left bank of that 
river opposite to Coblentz; and in some places these beds of 
pumice-stones are intermixed with distinet beds of cinders, thrown 
up at some intervals from the crader of these volcanoes. But on 
this subject, as on the aqueous origin of our mineral strata, 
there are too many circumstances all to be mentioned here; 1 
must therefore refer the author to my descriptions. 
These are not the only remains of ancient volcanoes observed 
on our continents. 1, a new geological work which f have lately 
published, under the title of Geological Travels through some 
Paris of France, Switzerland and Germany, | have deseribed in 
the northern parts of the latter country a multitude of lasaltic 
hills, which evideutly are volcanic from the nature of their sub- 
stance ; but they are particularly interesting, as they afford a new 
proof that some /avas come out from the botiom of the sea: these 
lavas from their natures when meeting red-hot the water of the 
sea, were broken into the prismatic form of Lasaltes. 
Of this effect my brother has seen an instance belonging to 
modern volcanoes on the coast of Sicily, near Catana, A lava 
having flowed from the side of Mount Etna down to the sea, the 
part which remained on the avd retained the land all 
avas 3 
