A HISTORY OF CUMBERLAND 
published in the Quarterly Fournal of the Geological Society of London, vol. 
x., by Miss Ellis. 
II. We may now turn to the fuller consideration of the volcanic 
episode to which brief reference has just been made, and in connection 
with which so much that is of geological interest in the present Lake 
district is intimately concerned. The history of the volcanoes cannot be 
completely made out ; but we already know quite enough to give us a 
much clearer view, as we look back into the past, than is possible in the 
case of the Skiddaw Slates. One thing is quite clear: the volcanoes 
began with a series of extremely violent eruptions, in the course of which 
the explosions tore away vast quantities of the older sediments through 
which the volcanic vents arose, and ejected those fragments to a con- 
siderable distance from their starting-point. It is not a little remarkable 
that fragments of lava in many cases form but a small proportion of these 
ejected materials from the earlier-formed vents. Fragments of the Skid- 
daw Slates abound in these old tuffs, thereby proving, if proof were still 
needed, that the volcanic rocks are of /ater date than the rock referred to. 
On theoretical grounds we may suppose that these violent paroxys- 
mal explosions were due to the water finding its way down through the 
outer zones of the lithosphere (or rocky crust of the earth) to the inner 
zones, where, from one or other of several possible causes, there existed 
a temperature sufficiently high to produce conditions favourable to the 
generation of new compounds. Heated waters, containing but a small 
percentage of the alkalies present in combination in sea water, are com- 
petent to dissolve almost any rock material known, and are able to do so 
at a comparatively low temperature—far below that which lavas have 
when first poured out of a volcano. A compound of the nature referred 
to possesses violent explosive properties, and, indeed, can only be kept 
from exploding by the influence of enormous pressure. If by any ter- 
restrial movement the pressure at the critical time happens to be relieved, 
liquefaction at once commences, and steam in a highly explosive condition 
is generated throughout the area where the pressure has been eased off. 
Under these circumstances the fluid rock material begins to eat its way 
in the direction of least resistance, and finally reaches the surface, where 
the pressure is relieved by a succession of more or less violent detonations, 
whose general nature may be likened to that of boiler explosions. One 
of the determining causes of both a local rise of underground tempera- 
ture and a spasmodic relief of pressure must have been the local bendin 
of the outer part of the lithosphere to which reference has already been 
made. Indeed, it seems unnecessary to invoke any other factors in the 
generation of volcanic action than this local conversion of the energy of 
motion into heat energy, combined with the downward transference by 
osmosis of alkaline waters from the floor of the ocean, and the subsequent 
release of the imprisoned gases by the local and spasmodic relief of pres- 
sure which accompanies the folding mentioned above. 
The Cumberland volcanoes were probably small to begin with, and 
probably there were several in an irregular line ranging southward 
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