goo JDr, Richardson's Letter on the basaltic Surface 
Tenth Stratum. ( a ) 
The stratum upon which the pillars of the preceding rest, is 
ochreous, red as minium, and about twenty feet thick ; it is 
scarcely seen at Port moon, a patch alone of its surface being 
distinguishable under water at low tide ; but immediately to the 
northward it shews itself, and from its bright colour makes a 
conspicuous figure across the face of the precipice in a course 
of more than a mile and half ; its last appearance to the west- 
ward is at Rovinvalley , the opposite point of the bay from the 
Giant’s Causezvay, from which we have a good view of it. The 
final dip and immersion of this tenth stratum, as well as its 
emersion, are lost for want of perpendicularity. 
The six remaining strata are all similar in material, but 
differing much from each other in thickness ; they are all of 
that description called tabular basalt, sometimes shewing a 
faint disposition to assume a columnar form at their edges, 
and always separated from each other by ochreous layers. 
These six strata are not so perfectly distinct as those above 
them, for sometimes we think we can count seven, and again 
not more than five ; nor does each of these preserve the same 
thickness through their whole extent, for they are deeper 
towards the northern point, where they culminate,* forming 
by themselves a perpendicular fa£ade near two hundred feet 
high, but they grow thinner as they recede from this centre. 
The jets of black rock in the view of Portmoon, are the 
emersions of these strata ; their last appearance on the west 
side is at Rovinvalley , where they strongly display the incli- 
nation of their strata, (the same with all the rest) to those 
approaching from the westward ; their final immersion is lost 
for want of perpendicularity. 
