THE CHEMICAL EXAMINATION OF THE MATERIALS FROM FUNAFUTI. 377 



Boring, there being little evidence that the proportion of magnesium carbonate 

 increases in going downwards to the limit reached of 245 feet. 



I have not been able to obtain any analysis of perfectly fresh Lithotliamyiioii , but 

 probably the fact that new living layers are constantly spreading over dead ones 

 would make any result untrustworthy. Many chemists, however, have found in dead 

 specimens of Lithothamnion a quite abnormal proportion of the magnesium carbonate. 

 Thus GtJMBEL gave the proportion of magnesium carbonate to calcium carbonate in 

 a specimen of Lithothamnion nodosum, Kutz. sp., as 5 '58 to 84 "14, equivalent to a 

 percentage of 6 "6 2 of magnesium carbonate in the total carbonates,* this being the 

 mean of several analyses. Walther in 1885 gave the composition of the mineral 

 matter in a very compact species of Lithothamnion, as 3 "99 of magnesium carbonate 

 to 85'87 of calcium carbonate (= 4"44 per cent, of the mineral matter). A specimen 

 of Lithothamnion ramulosum gave, to the same author, 6 '42 of magnesium carbonate 

 to 81 '93 of calcium carbonate (= 7 "15 per cent, of the mineral matter).! 



Very striking, indeed, are the results of a similar kind obtained by Hogbom from 

 the analysis of a considerable number of museum specimens of Lithothamnion. 



These results may be tabulated as follows :— 











Percentage of 



Speciea. 



Locality. 



Calcium 

 carbonate. 



Magnesium 

 carbonate. 



magnesium 



carbonate in 



mineral matter. 



Lithothamnion, sp 



Java Sea . . . 



72-03 



3-76 



4-96 





, ,,.... 



Pliocene, Tarent 



89-97 



6-49 



6-73 





, ,,.... 



Galapagos Is. . 



83-60 



6-53 



7-24 





) ))•••• 



Spitzbergen . . 



84-83 



8-07 



8-69 





5 ,,.... 



Honolulu. . . 



84-01 



9-39 



10-05 





, sorifern . . 



1 



80-90 



9-56 



10-57 





, polymorphwm . 



Kattegatt . . 



74-22 



9-10 



10-93 





sp 



Behring's Is. 



74-24 



9-94 



11-82 





, racemus . . . 



Naples ... . 



77 - 39 



11-33 



12-77 





, ramulosum . . 



,, ... 



63-00 



9-46 



13-05 





sp 



Bermudas . . 



82-44 



12-37 



13-05 





, glaciate . . . 



1 



83-10 



13-19 



13-70 



A specimen of Lithothamnion Pkillipi, var. funafutiensis, Foslie, which retained 

 in its outer layer the purple tint, usually so fugitive, and which was evidently 

 collected in a living state, so far as this outer layer is concerned, yielded to 

 Dr. Skeats on analysis no less than 5 '8 6 of magnesium carbonate. The mass was 

 nearly 1 inch in thickness, and, except in the purple surface layer, was white and 

 crumbling. 



All these analvses noint to the conclusion that the calcareous algse, Halimeda and 



* ' Abhandl. Bayer. Akad. Wissenchaft.,' vol. 11 (1871-74)), p. 26. 

 t ' Zeitsch. d. Deutsch. Geol. Gesellsch.,' vol. 37, 1885, p. 338. 



3 



