497 
Dr. Berger’s Account of the Isle of Man . 
I observed five dykes in this neighbourhood, three to the north 
and two to the south of the tuff. The composition of all these is 
nearly the same, consisting of a tolerably close grained basalt, the 
northernmost containing a great quantity of olivine. Fig. 4, 
Plate 31, represents the horizontal section of this dyke formed on 
the beach. They all intersect the stratified limestone, and one also 
cuts through the tuff. They do not appear to alter the nature of 
the limestone, except in one or two places, where it has become 
white and charged with a quantity of argillaceous matter, but at 
the immediate contact it is filled with specks of basalt and crystals 
of hornblende, which are entirely embedded in the manner already 
mentioned with respect to those portions which have been entangled 
in the tuff. 
Explanation of the Sketch, fig. 6, PI. 35. 
a , basaltic dykes. 
b 9 confused mass of crystalline limestone, mixed with fragments 
of quartz. 
c 9 crystalline limestone rising through the regular strata, containing 
many fossils. 
d 9 the more compact portion of the trap, which is amygdaloidal 
and porphyritic. 
A dyke, similar in character to these, occurs at Brada, running 
parallel to the course of the metallic vein along the coast to the 
north of the Head. 
The strata towards the southern side of Langness are much 
intersected by dykes of greenstone. 
A bed of greenstone, in which the hornblende is remarkably 
well crystallized, occurs to the south of Port-le-Murray. It may 
3 r 2 
