y. THE DEPOSITS OF THE SEA-BOTTOM. 



Having thus accounted for the rocks and mineral ingredients of the single specimens, it will 

 be necessary for the general view to say a few words of the distribution of each of these ingredients, 

 before passing to more general reflections on the distribution. Of the volcanic material is to be 

 named primarily: 



Basalt, which occurs widely distributed in the specimens in many varieties: the most common form 

 is a black or black-gray, compact or very fine-grained basalt forming the chief portion of 

 Iceland and the Faroe Islands, and found in almost all the specimens from the vicinity of 

 these islands, being often the chief ingredient of the specimens, and sometimes the only 

 ingredient of the coarser particles. Of the 79 specimens in which ingredients over a diameter 

 of o-5 mm are found, the compact basalt is found in 53, and in 18 specimens it is more than 

 half of all the ingredients; these latter specimens are almost all found in close vicinity of 

 Iceland, where the terrigenous material has not been mixed up with material from other 

 places; besides, especially large masses of basalt are found between Iceland and Jan May en; 

 accordingly the circumstances must be especially favourable for transport from Iceland in 

 that direction. A single specimen, no. 140, north of the Faroe Islands, occupies a peculiar 

 position, containing, contrary to the neighbouring specimens that are rich in quartz, nothing 

 but 5 pieces of black basalt; but these may well be supposed to have arisen from one single 

 piece that more or less casually may have been carried to this place, while the circum- 

 stances have otherwise been of such a nature as not to allow coarser material to be depo- 

 sited in the said place. Among the specimens from Greenland, small, dubious pieces of 

 basalt have been observed from a single station, no. 29; they may be supposed to have ori- 

 ginated from the Greenland basaltic region farther north. In the basalt small grains have 

 often been observed of feldspar, olivine, augite; more rarely small cavities are found filled 

 with some white mineral, either chalcedony or zeolites. Sometimes the basalt assumes a 

 more brownish or reddish colour; it is often, like several of the other ingredients, covered 

 on the surface by a dark, red-brown crust, which crust may either be formed by disintegration 

 or else by the surrounding water having contained dissolved iron, and deposited it on the 

 grains as ferric oxide; that this process has taken place in many cases, may be seen from 

 the fact that also the grains of quartz and other grains that cannot decay, are often covered 

 with a similar brownish crust Sometimes the basalt has been totally disintegrated, and 

 has passed into a rather loose, brownish rock, chiefly observed in the specimens between Iceland 

 and Greenland. Very commonly the basalt is found to be quite filled with small cavities; 

 the designation of porous basalt has been used, when the elementary matter is compact, 

 while the rock has been put down as vesicular glass or pumice, when the elementary matter 

 is glassy. The porous basalt has been observed in 20 specimens, situated to all sides 

 of Iceland, mostly, perhaps, to the southeast; in three of these specimens it forms the chief 

 portion of the ingredients, viz. no. 80, southwest of Iceland, no. 106, east of Iceland, and 

 no. 125, north of Iceland; thus it would seem, as if this rock and the compact basalt may 

 arise from all sides of the island indiscriminately. 



