REPORT ON THE DEEP-SEA DEPOSITS. 
307 
After the above description of basic glasses and of palagonite, it is important to show 
that our determinations are supported in all points by the results of chemical analysis. 
We give first the analyses of three compact, black, vitreous fragments from Stations 276, 
285, and 302, all in the South Pacific. The fragments analysed presented all the 
characters above indicated for fragments of compact basic glass, in which by means of the 
lens small crystals of olivine alone could be distinguished. 
Station. 
Depth in 
Fathoms. 
No. 
SiO^ 
AI 2 O 3 
FeO 
MnO 
CaO 
MgO 
K 2 O 
NagO 
P2O5 
Total. 
276 
2350 
93 
46‘76 
17-71 
1-73 
10-92 
0-44 
11-56 
10-37 
0-17 
1-83 
101-49 
285 
2375 
82 
49-97 
11-68 
2-45 
10-60 
traces 
11-20 
12-84 
0-25 
1-60 
0-33 
100-92 
302 
1450 
95 
46-84 
17-78 
1-64 
10-79 
0-34 
11-87 
9-24 
0-28 
2-02 
100-80 
It is evident, after the examination of the above figures, that the determination of these 
fragments as belonging to the basic glasses is established in an incontestable manner ; 
they must be referred to the lithological family comprising the basalts. 
It remains now to indicate the results of the analysis of the palagonitic matter 
which covered the fragment made use of in Analysis No. 93. 
Station. 
Depth in 
Fathoms. 
No. 
SiOg 
AI 2 O 3 
MnaOg 
CaO 
MgO 
K 2 O 
Na 20 
H 2 O 
Total. 
276 
2350 
94 
44-73 
16-26 
14-57 
2-89 
1-88 
2-23 
4-02 
4-50 
9-56 
100-64 
In comparing this analysis with that of the anhydrous silicate (Analysis No. 93) from 
which this palagonitic matter was derived, it may be observed that the latter is produced 
by the hydration of the former; it contains, in fact, 9 '56 per cent, of water. The 
transformation which has taken place seems to tend to the formation of a zeolitic sub- 
stance ; lime and magnesia are eliminated, the protoxide of iron passes into peroxide, 
alkalies derived from the action of sea-water enter into combination, the quantity of 
alumina remaining almost constant. 
Palagonitic Tufas . — This name was introduced by Sartorius von Waltershausen to 
designate certain tufas found in Iceland, Sicily, Galapagos Islands, and other regions, 
composed principally of fragments of basic volcanic glass, like those described above, along 
with other volcanic lapilli chiefiy belonging to the basic series. These tufas are known 
to have been deposited under water, and in some cases the materials were probably 
derived from submarine eruptions.^ In many regions of the deep sea tufas in every way 
analogous to these palagonitic tufas were discovered by the Challenger Expedition, 
associated with extensive depositions of peroxide of manganese, and frequently forming 
the nuclei of manganese nodules. 
^ See A. Penck, “ Ueber Palagonit- und Basalttuffe,” Zeitsch. d, d. geol, Gesellsch., 1879, pp. 504-577. 
