252 
GREENLAND VOYAGE. 
sustained. Occasional unequal veins of green¬ 
stone, and different varieties of porphyry, occur to¬ 
wards the summit of the cliffs, and in some places 
appear to intersect the pinnacles. 
About the middle of Vandyke Cliffs, where the 
beautiful structure of the rocks, and fine alterna¬ 
tions of colour are observable, the slate-clay, in its 
vertical arrangement, forms lanceolate pinnacles, 
and is repeatedly intersected, in waving lines, run¬ 
ning horizontally, with yellow and red-stained 
porphyry; so that the hack pinnacles, as they pro¬ 
gressively attain a greater elevation, and become 
visible one over another, present numerous paral¬ 
lel zig-zag or serpentine hands of various colours. 
These striking colours, which are remarkably 
bright, were traced to the decomposition of iron- 
pyrites. The yellow bands, or veins, were found 
to consist of whitish porphyry, containing a great 
abundance of imbedded grains, and small cubical 
crystals of common iron-pyrites, by the decompo¬ 
sition of which the yellow incrustation on the sur¬ 
face was produced. The red bands were either 
porphyry or slate-clay, which also obtained their 
colour from an incrustation with the decomposed 
pyrites, in a different state of oxidation. 
This interesting part of the country appeared 
to be principally composed of secondary or floetz- 
trap, and secondary porphyry. Both these rocks 
