318 PROF. HARBISON AND ME. JUKES-BROWNE ON [Aug. 1 895,. 



On consulting Dr. Murray's volume we found that, as a matter of 

 fact, minute fragments of volcanic glass and palagonite were found 

 in this particular Red Clay, as well as several pieces of pumice, ' one 

 of which was red in colour and appeared to be undergoing altera- 

 tion' (op. cit. p. 117). Fragments of basic volcanic glass are 

 indeed described as common in all deep-sea deposits, and as especially 

 abundant in the Eed Clay areas of the Pacific. The characters of 

 such glass and its manner of decomposition are also discussed, and 

 an analysis of the palagonitic matter is given on p. 307 of the 

 ' Challenger ' Report. This analysis (B) we place side by side with 

 that of the clay isolated by our analysis re-calculated to a percentage 

 composition (A), and also one of a palagonite (C) from Climbach, 

 near Giessen (Streng, Neues Jahrb. 1888, vol. ii. p. 224), for the 

 reference to which we are indebted to Mr. J. J. H. Teall, F.R.S.: — 



A. B. 0. 



Silica 49-67 4473 50-02 



Alumina 17-91 1626 13-06 



Peroxide of iron 15-31 14-57 1760 



Peroxide of manganese 2*29 2 - 89 — 



Lime 1-02 1-88 2"82 



Magnesia -82 2-23 4-57 



Potash 1-35 402 -55 



Soda 2-33 450 -84 



Water 931 956 10-54 



10001 10064 10000 



We do not doubt that the decomposition of the basic pumice 

 which is also very abundant in tbe Pacific would result in the 

 formation of a similar material. The close connexion between this 

 pumice and the volcanic glass is shown by the following analyses 

 taken from the ' Challenger ' Report (pp. 297, 307) :— 



Basic Basic Basic 



Glass. Glass. Pumice. 



1. 2. 



Silica 46-76 49-97 50-56 



Alumina 1771 11-68 1030 



Ferric oxide 1'73 2-45 4-95 



Ferrous oxide 10-92 10-60 7"59 



Manganese oxide '44 traces -14 



Lime 11-56 1120 9-35 



Magnesia 1037 12"84 9"27 



Potash -17 -25 1-24 



Soda 1-83 1-60 2'81 



Titanic acid — — '80 



Water — — P70 



101-49 100-59 98-71 



The clay is formed by the hydration and oxidation of these sub- 

 stances in the presence of sea-water. Dr. Murray remarks that, in 

 comparing the analysis of the palagonite with that of the anhydrous 

 silicate from which it was derived, it is seen that ' lime and magnesia 

 are eliminated, the protoxide of iron passes into peroxide, alkalies 

 derived from the action of sea-water enter into combination, the 



