168 EFFECTS of HEAT 
as pipes through which the lavas of the lateral eruptions were 
conveyed to the open air. This fcene prefents to the view 
of an attentive obferver, a real {fpecimen of thofe internal ftreams 
which we have juft been confidering in fpeculation, and they 
may exhibit circumftances decifive of the opinions here ad- 
vanced. For, if one of thefe ftreams had formerly been con- 
nected with a lateral eruption, difcharged at more than 600 
feet above the Atrio del Cavallo, it might poffibly contain the 
carbonate of lime. But could we fuppofe that depth to extend 
to 1708 feet, the interference of air-bubbles, and the action 
of a ftronger heat than was merely required for the fufion of 
the carbonate, might have been overcome. 
Peruaps the height of Vefuvius has never been great enough 
for this purpofe. But could we fuppofe AZtna to be cleft in 
two, and its ftructure difplayed, as that of Vefuvius has juft 
been defcribed, there can be no doubt that internal ftreams of 
lava would be laid open, in which the preflure muft have far 
exceeded the force required to conftrain the carbonic acid of 
limeftone ; fince that mountain occafionally delivers lavas from 
its fummit, placed 10.954 feet above the level of the Mediterra- 
nean *, which wafhes its bafe. I recolleé& having feen, in fome 
parts of Etna, vaft chafms and crags, formed by volcanic re- 
volutions, in which vertical ftreams of lava, fimilar to thofe of 
Somma, were apparent. But my attention not having been 
turned to that obje@ till many years afterwards, I have only 
now to recommend the inveftigation of this interefting point 
to future travellers. 
Wuart lias been faid of the heat conveyed by internal volca- 
nic ftreams, applies equally to that deeper and more general 
heat by which the lavas themfelves are melted and propelled 
upwards, 
* Phil. Tranf.17474, p. $95- 
