420 
HARBOUR OF INEADA, 
chap, consist is a decomposed and crumbling porphyry ( 
V. , -,-. so imperfectly adhering, that upon the slightest 
shock it falls to pieces. Climbing the sides of 
the cliff, we found it to be dangerous even to 
place our feet upon any of those pillars ; whole 
masses giving way with a touch, and, falling 
down, were instantly reduced to the state of 
gravel. Nuclei of an aluminous substance might 
be discerned in the very centre of their shafts ; 
and white veins, of an exceedingly soft crum- 
bling semi-transparent matter, not half an inch 
in thickness, traversed the whole range, in a 
direction parallel to the base of the columns. 
The vertical fissures between all the pillars were 
filled with a white kind of marble, forming a line 
of separation between them, which prevented 
their lateral planes from coming into contact'. 
Those vertical veins, thus coating the sides of 
the columns, were in some instances three 
Theory of inches in thickness. From all these facts, it 
then ongin. geemg ev i<jent that the basaltic pillars of Ineada 
have been the result of an aqueous deposition 5 
and that their prismatic configuration, like that 
of starch, or the natural columns of trap, seen at 
(l) A similar incrustation of zeolite may be observed upon the 
lateral planes of the pillars at Staff'd, and upon the north coast of 
Ireland ; also of sparry carbonate of lime in pit-coal , when it exhibits a 
near approach towards crystallization. 
