46 
are due to the presence of chlorite diffused through the rock, in a 
greater or less degree, the red and purple tints being due to hematite. 
There is generally more or less stratification discernable in the 
ashes, shown in some cases by clearly defined bands of light and 
darker colour, and in others by fine and coarser materials. These 
alternating beds or layers of finer and coarser ash are often very 
irregular, some layers thinning out and others thickening; and 
occasionally very clear examples of false-bedding are seen amongst 
the finer varieties. Sometimes a single fragment of older rock of 
considerable size, showing all its original structure, may be seen 
embedded in a mass of fine ash. 
The materials of which the coarser ashes and breccias are 
formed, consist chiefly of fragments of older ashes and lavas, but 
in the purple breccia, at the base of Falcon Crag or Bleaberry Fell 
section, which is probably the oldest member of the volcanic series, 
there are numerous fragments of altered Skiddaw Slate. ‘The fine 
ash has no doubt been formed of the same material as that which 
is sometimes ejected so copiously from modern volcanoes when in 
a state of activity, and which is merely lava reduced to powder bya 
succession of violent explosions of steam and gas; indeed, the 
ashes, breccias and lavas of the Borrowdale series afford abundant 
evidence in their structure and composition that they were derived 
from a similar source, and in a similar manner to the beds of 
recently formed volcanic ejectamenta which may_be seen surround- 
ing the cone of an active volcano. 
All the rocks of the volcanic series, as well as the underlying 
Skiddaw Slates, have been subjected to great lateral pressure, 
caused in all probability by the shrinking of the earth’s crust in 
cooling; and this pressure, which acted in a N.E. and S.W. direction, 
has produced cleavage in a higher or less degree in nearly all the 
beds of both these formations, by causing them to expand in a 
direction perpendicular to that in which the pressure was applied, 
the particles constituting the rock being flattened and rearranged 
during the process, with their longer axis in the direction in which 
the expansion was made. This change in the structure of the rock 
causes it to split readily across the old planes of stratification at a 
