OF DISKO ISLAND, 265 





To the north of Kakarsoak, in the colony of Upemavik, in 

 Lat. 72° 3%, the floetz-trap again disappears, and granite, al- 

 ternating with gneiss, present themselves, and continue to 

 Lat. 73° 32^ at the islands of Udjordlersoak and Tessiursak. 

 Near Cape Nullok, in Sanderson's Hope, the floetz-trap again 

 appears in large masses of columnar basalt, resting on gneiss ; 

 but beyond this place, there is no farther approach, the coun- 

 try being covered by the Great Boreal Glacier, — the Northern 

 IceSlink. 



The direction of the trap-rocks, which are here spread over 

 such an extent. of country, is almost entirely similar, being 

 nearly horizontal, stretching from south-west to north-east. 

 The beds of which they are composed are of a very unequal 



^ thickness: those of basalt are most prevalent. The hills com- 

 posed of gneiss and granite are never highly elevated ; and the 

 floetz rocks are placed immediately on the gneiss, which is al- 

 ways slightly decomposed upon the surface, where in contact 



f ' with the trap. The prismatic basalt of this district, is of that 

 species distinguished in Germany by the name of Basaltic 

 Greenstone, ( Griinsteinartiger Basalt ) . It is almost pure, but 

 sometimes contains a few detached specks, perhaps crystals of 

 felspar. I found only in one place some small grains of augite 

 and of hornblende. The massive basalt, on the contrary, often 

 becomes amygdaloidal, by the small globules of mesotype, stil- 

 bite and quartz which it contains. It occurs very generally 

 undermost, and touching the primitive rocks, which is very 

 rarely the case with the columnar basalt. 



The Trap-tuff, which is very common among the floetz rocks 

 of Disko, rests also always immediately on the primitive rocks : 

 Indeed, I never found it in any other situation in that island. 

 It appears to me here necessary to mark two varieties of 

 this rock, namely, that which consists almost entirely of frag- 



l 1 2 ments 





it 





