THE DEPOSITS OF THE SEA-BOTTOM. 2 c 





Section III. 

 The Mineralogical Nature of the Bottom-Specimens. 



See the charts on plates 5 — 7. 



The object of the present section is to show the nature of the mineral ingredients of the 

 specimens, and, as far as possible, refer the rocks and minerals to their place of origin. This latter 

 can, of course, only be made partly, even if the territory explored by the Ingolf expedition, shows 

 rather great advantages in this respect. Scarcely anywhere will be found a more marked difference 

 with regard to petrography than that existing between Iceland, the Faroe Islands, and Jan Mayen 

 on one side, and Greenland, Scandinavia, and perhaps land farther to the north on the other side, and 

 from these sources the bottom-specimens have received all their mineral material, with the only ex- 

 ception of the few ingredients that may have come from the sea-bottom. But it has been quite im- 

 possible to refer the different rocks to particular localities within these territories, and especially on 

 account of the fact that the coarsest ingredients of the specimens very seldom reach any considerable 

 size; by far the greatest number are smaller than 2 mm in diameter, and only a few pieces have sur- 

 passed the size of a pea. Consequently it will in most cases be impossible to refer the ingredients to 

 a particular rock, and still more impossible to refer this rock to a particular locality; very often each 

 grain is made up of only one single mineral, and even if it be an aggregate of more minerals, it will 

 generally, on account of its smallness, not be able to show the structure characteristic of the rock in 

 question, with sufficient distinctness. To this is to be added that the rocks in each of the two men- 

 tioned groups of lands are rather homogenous. From Greenland and Scandinavia the ingredients are 

 almost exclusively of gneiss and granite, and, far the most predominant, of quartz, and those ingre- 

 dients cannot be referred to any particular locality inside this large territory; the rocks and minerals 

 from the Faroe Islands are, in the condition in which they are found in the bottom-specimens, scar- 

 cely to be distinguished from the Icelandic ones, whereas part of these latter will not be found in the 

 Faroe Islands. The ingredients from Jan Mayen may easily be distinguished from those from Iceland, 

 but they are only found in close vicinity of the island. 



In the following the mineral ingredients of the two larger sizes of grains will be examined, 

 while the finer particles will only be treated briefly, they being partly rather difficult to distinguish, 

 and partly of about the same nature as the coarser ones. The ingredients over 0-5""" are generally 

 directly recognizable, and it has only in a few cases been necessary to subject them to a closer micro- 

 scopic examination; the ingredients between 0-5— o-05 mm , on the other hand, have chiefly been examined 

 by means of a microscope. On account of the different methods of examination, I have thought it 



The Ingolf-Expedition. I. 3. 4 



