PetrograpMco-geological Description. 



I. Archæan rocks. 



As already stated, the archæan rocks constitute the bulk 

 firstly of all the Greenland central mass, and secondly, within 

 the tract with which we are here concerned, of the isolated 

 and elongated peninsula north of Scoresby Sund, called Liver- 

 pool Land. Already by reason of their position, far from each 

 other, each of these tracts must be dealt with separately, and 

 the same applies to the various districts situated far from one 

 another at the bottom of the great fjords, where up to now 

 opportunity has been afforded of getting to know the structure 

 of the central mass. The following description will therefore 

 be an account of the different localities. 



A. Structure of the Central Mass within Scoresby Sund. During 

 the Expedition of 1900 we never penetrated so far into this 

 fjord that I had an opportunity of studying the features of the 

 primary rock in situ. The Ryder Expedition of 1891 — 2, on 

 the other hand, brought back from here a considerable collec- 

 tion of rocks, which I had an opportunity of examining both 

 as specimens and in thin sections, and on these, as well as on 

 the description given by Bay^), the following summary is based. 



The material in question, taken from a considerable area, 

 shows that the rocks there are unexpectedly uniform and consist 

 almost everywnere of gneiss, usually grey micaceous gneiss, 



M Medd. om Grønland. XIX, 147 seq. 



