CHAP, XXIX 
THE ISLE OF MAN 
29 
so far as can be observed, lies in tbe agglomerate — a large cake of white 
limestone with pebbles of quartz, which has probably been broken off from 
some underlying bed and carried up in the chimney of the volcano. 
As a rule the agglomerate is a tumultuous, unstratified mass. But in 
many places it shows lines of bedding and, as already stated, passes outward 
dito ordinary bedded tuff, the number and size of the ejected blocks rapidly 
diminishing. Where this transition occurs we seem to see a remnant oi 
file base of the actual volcanic cone. Thus, in the most westerly vent 
already cited, while the wall of the vent has been laid bare on the side next 
fde sea, so that the agglomerate on the beach descends vertically through 
file surrounding bedded tuffs, on the western side the cliffs have preserved a 
Portion of the material that accumulated outside the orifice (Fig. 187). 
Piq. 187. — Section of part of a volcanic neck on shore to the south-east of Poyll Vaaish Bay, 
Isle of Man. 
this section we observe that the coarse agglomerate which fills tip 
fhe main part of the vent has been left with a hummocky, uneven surface, 
<u id that a subsequent and perhaps feebler eruption of finer material has 
covered over these inequalities, and has extended to the left above the fine 
fuffs through which the agglomerate has been drilled. 
Again, in the largest of the vents, that near Scarlet Point, still 
clearer proof of successive eruptions and dislocations within a volcanic 
lG * 188. Section of successive discharges and disturbances within a volcanic vent. Scarlet Point, 
Isle of Man. 
chimney may be noticed. At one point the accompanying section (Pig. 
f b8 ) has been laid bare by the waves. The oldest accumulation is a fine 
pen granular tuff («), rudely and faintly arranged in layers inclined at 
'(gh angles, like the fine materials in many of the vents of the basin of the 
lrtb of Forth. This peculiar stratification, due not to the assortment of 
