THE NATUEE OF THE INTEEIOE OF THE EAETH. 
By DAVID FORBES, F.R.S., &c. 
W HAT the central mass of the globe upon which we live 
consists of, is a question which most educated men have 
doubtless at some time or other asked themselves, without, it is 
surmised, eliciting a response which could in any degree satisfy 
their natural curiosity; most probably the idea which would 
first suggest itself, is, that its internal mass must be composed 
of solid rock similar to what is seen forming its mountain chains, 
the foundations of its continents and the basins which contain 
its seas. The belief in this hypothesis would, however, be rudely 
shaken upon the first experience of the effects of an earthquake, 
or the sight of a volcano in activity, for such phenomena could 
not but at once suggest grave doubts as to whether the earth 
could be in reality either so solid or so stable as at first thought 
one felt inclined to believe. 
Such phenomena, however rare they may be in G-reat Britain, 
are not exceptional, as the intelligence from all quarters of the 
globe testifies. During the past year, scarcely a mail has arrived 
without bringing tidings from some part or other of volcanic 
outbursts or earthquakes, several of them fearfully disastrous ; 
now taking place near the North Pole, as in Iceland or Alaska, 
then in the Antarctic regions of Polynesia or New Zealand, whilst 
still nearer home Vesuvius and Etna have alternated in fiery 
activity. Extensive eruptions and earthquakes have also occurred 
within the last twelve months in the West Indies, Sandwich 
Islands, California, Mexico, Nicaragua, and in various parts of 
the Andes of South America ; yet even this enumeration is far 
from being a complete one. 
Nor have the continents, or, as the Spaniards say, ^^Tierra 
firma,” been alone so affected, for numerous accounts also bear 
witness that the depths of the sea have been equally disturbed. 
In the Mediterranean, for example, the sea bottom at Santorin 
has been so elevated by volcanic action as to have become dr}" 
land, where only lately was deep water in which the largest ships 
afloat could ride at anchor ; and submarine eruptions of great 
