56 



THE DEPOSITS OF THE SEA-BOTTOM. 



same refraction as the Canada balsam, we shall see no shadow; this is the case with a few of the 

 brown grains that may perhaps be supposed to consist of a very dark obsidian, while the majority 

 consists of basaltic glass. The colourless glass differs also from the brown glass by the form of the 

 grains, as it consists either of very thin and flat leaves, or else is strongly produced in one direction 

 so as to be filamentous; this latter form approaches somewhat to that before mentioned in the brown 

 glass with lengthened air vesicles. The colourless glass has been met with altogether in 67 specimens, 

 distributed over the whole territory; as it originates from the pumice that may float about everywhere, 

 we may expect to find it in all specimens from all parts of the earth, though on most places only in 

 small quantities. At the west coast of Greenland it is found in several specimens; but south and 

 southwest of Greenland it is wanting; in most of the other specimens it is found with a few dispersed 

 exceptions; in some, more limited regions, it is found in larger quantity, viz. in some specimens west 

 of Iceland, a series of specimens between Iceland and Jan Mayen, a very little territory north of the 

 Faroe Islands, and a series of specimens east of Iceland; this latter territory is remarkable by almost 

 exclusively containing the filamentous form, otherwise not very conspicuous, while the other territories 

 contain the glass in thin, micalike leaves. The causes of this distribution are not easily explained; 

 whether they have to be sought in particular volcanic eruptions and showers of ashes or in an abundant 

 transport into the sea in these territories, is very dubious; it is upon the whole almost always impos- 

 sible to decide, how great a part the showers of ashes play with regard to the deposits of the sea- 

 bottom. The fact is that volcanic ashes may contain as well intransparent as brown, opaque grains, 

 and brown and colourless glass, so that they will most likely disappear entirely between the other in- 

 gredients. The different territories for larger quantities of the colourless glass never reach quite to 

 the land, what is at all events easily accounted for by the fact that the pumice is not to the same 

 degree as the other ingredients deposited upon a larger scale closer to the land than farther oiit in 

 the sea, and consequently it will in the former place easily disappear between the other ingredients. 

 The garnet is very conspicuous in the preparations, partly on account of its comparatively 

 great refraction that is about equal to that of the augite, partly by the colour, after which it may be 

 divided into three sorts, red garnet or almandine, dark, violet garnet or melanite, and brownish garnet 

 or cinnamon stone. It is found in the specimens as an absolute Greenland material; but on account 

 of its imperishableness it may like the quartz be widely distributed, though, of course, in far smaller 

 quantity. Thus the almandine has been found in 17 specimens very far from Greenland, spread over 

 the whole territory. At the coasts of Greenland it has been found in larger quantity in no. 94 on the 

 east coast, and in several of the specimens on the west coast, in especially large quantity in some of 

 the northernmost ones, while it is quite wanting or rather scarce in the southern ones. The melanite 

 is found in especially large quantity in the northernmost of all the specimens on the west coast of 

 Greenland, no. 53 with 13-5 per ct, in rather large quantity in the two more southern specimens, 

 nos. 32, and 31; for the rest it is found evenly distributed in all the specimens from the west and 

 south coast of Greenland. On the east coast it is found in larger quantity in no. 94, viz. 4 per ct; 

 when we get farther out it is not nearly so widely spread as the almandine, it has only been found 

 in 5 specimens, all west and southwest of Iceland, and only in small quantities, partly only in a single 

 piece. The cinnamon stone has only been found in two specimens, viz. in no. 51 at the northern part 



