A. Milward, Esq., 0” the Motion of a Lava-Stream. 51 
was seen through the cracks of the superficial scorie. I 
particularly examined two of these luminous places, but shall 
chiefly confine my description to one of them, and refer to 
any difference worthy of notice in the other. The most 
striking characteristic of the great mass of lava on the south 
side of the mountain, was that of irregular heaps, fantastic 
projections; but from an elevated point, longitudinal ridges, 
and something like transverse ones, were suficiently appa- 
rent. The hot lava presented the curious phenomenon of 
flowing along the tops of these longitudinal ridges, so as to 
occupy the highest ground. I have reason to think that the 
greater part of the lava was still red hot, and plastic within 
little more than a foot or two of the surface. Where it 
pursued its course in a plastic state along the tops of the 
ridges, it evidently rose up from below like a spring, in con- 
sequence of the pressure from behind. A change in the in- 
clination of the mountain side, or some obstruction below, 
was probably the immediate occasion of this rise. I exa- 
mined particularly two of these streams which were not far 
from the east boundary of the lava, and where the black mass 
was still advancing slowly, and causing the small trees of a 
wood already partially destroyed, to bend before it from day 
to day. 
The hottest of the two streams was about a dozen or twenty 
yards distant from the margin of the lava, and rose through 
a small hole in the top of a ridge, assuming a breadth of three 
or four feet, and following the line of the ridge from which 
it had emerged. It gradually concealed itself, as it advanced, 
beneath black scoria, which rapidly increased in thickness, 
and then broke away in fragments, as I shall presently de- 
seribe. The lava, as it rose in an unbroken curve from the 
hole, was red hot, and perfectly homogeneous, free from 
scoriz or surface-markings of any kind. Its consistency was 
so great that the sides where the ridge fell away did not, for 
the space of six or seven yards, spread out over the cold lava. 
but advanced with a boundary nearly vertical, and about a 
foot in thickness,—apparently preserving so far the form 
which it had been forced to assume at its appearance. In 
consequence of this exposure, I could distinctly see the upper 
