
202 DYNAMICAL GEOLOGY. - < eBoow HT: = 
that the voleano formed at 
one time a large island with 
wocded slopes, and a some-— 
what civilized human popu- 
lation, cultivating a fertile 
valley in the south-western 
district, and that in pre-his- ~ 
toric times the tremendous 
explosion occurred whereby 
the centre of the island was 
blown out. 
The similarity of the 
structure of Santorin to that 
of Somma is obvious. Vol- 
canic action still continues 
there, though on a dimin-— 
ished scale. In 1866-67 an 
eruption took place on Neo 
Kaimeni, one of the later- 
formed islets in the centre of 
the old crater, and greatly 
added to its area and height. 
The recent eruptions of 
Santorin, which have been 
studied in great detail, are 
specially interesting from the 
additional information they 
have supplied as to the 
nature of volcanic vapours 
and gases. Among these, as 
already stated (p. 201), free 
hydrogen plays an important 
part, constituting at the 
focus of discharge thirty per 
cent. of the whole. By their 
eruption under water the 
mingling of these gases with 
atmospheric air and the com- 
bustion of the inflammable ~ 
compounds is there preven- 
ted, so that the gaseous dis- 
charges can be collected and 
analysed. Probably were 
operations of this kind more 
practicable at terrestrial vol- 
canoes free hydrogen and its 
compounds would be more’ 
abundantly detected than has 
hitherto been possible, 
district a non-volecanic tract in the 
herasia, an isiand composed, like 
with bedded tuffs and lavas; c, Mount St. Elias (568 metres), 
b] 
, Fig. 58) and forming with the surrounding 
e, Neo Kaimeni, the scene of the eruptions in 1866-67; /, T 




Fic. 59.—View oF THE INTERIOR OF THE CRATER OF SANTORIN FROM THE ENTRANCE. 
consisting of marble (shown by oblique lines in the chart 
midst of the lavas and tuffs; d, Mikro Kaimeni; 
Santorin, of beds of tuff, slags, and lavas. 

a, Town of Apanomeria, standing on tuffs, &c.; b, North-west cape of Santorin 
