217 



Witli regard to the origin of (he phosphorite of Ajtiwi there can 

 exist no doubt, but it was formed in the same way as the other 

 phosphates from the Pacific. From the investigations made in this 

 respect appeared that those ishmds were in former times atolls or 

 at least contained lagoons, into whicii the excrements of the birds 

 producing guano were washed by the atmospheric waters. The 

 phosphoric acid that had become free by the dissolution was the 

 cause that the coral-limestone surrounding the lagoons was changed 

 into phosphorite. The coral fragments that had come down to the 

 bottom of the lagoons, the boulders of limestone etc. were likewise 

 submitted to a similar metamorphosis, and were afler\vards cemented 

 into a compact rock '). 



Wherever such like phosphorites of coral islands make them- 

 selves apparent, it can only be the consequence of negative level- 

 changes. For this reason the rocks of Ajawi are to be considered 

 as the ruins of an original atoll, which has obtained its present shape 

 after subsequent upheaval t)y the waves of the sea. 



Now the question still needs to be answered, in what way the 

 absence of phosphorite in the islands of the Indian Archipelago can 

 be explained. For Ajawi belongs already to the territory of the 

 Pacific Ocean, and Christmas Island, 10°25', S. Lat. 105°42' E. 

 Long. '), rich in phosphorite is, it is true, situated in the Indian Ocean, 

 but its distance from the west-point of Java amounts to 420 km.. 

 so that it does not form any longer part of the Archipelago. 



As we have seen the conditions for the formation of phosphorite 

 in the Pacific were: the existence of coral islands with lagoons and 

 further deposits of guano. There is no doubt but there existed also 

 during the tertiary period a great number of coral islands. Neither 

 is it hazardous to suppose that in some of them settlements of guano- 

 producing birds were found. Consequently it seems to me that the 

 third condition — the existence of lagoons — was not complied 

 with, from which would follow that no more at that time than at 

 the present moment there were atolls in existence. At any case, 



^) 0. Stutzer. Ueber Phosphallagerstalten. Zeitschrift fur praiitische Geologie 

 19. Beilin 1911, pp. 81 — 82. — 0. Stutzer. Die wichtigsteu Lageistatten der 

 Nichlerze 1. Berlin 1911, pp. 488—440. — Paul Hambeuch. Entstehung, Bildiing 

 iind Lagerung des Phosphats auf Nauru. Zeilsclir. Gesellsch. f. Erdkunde. Berlin 

 1912, p. 679. — Already as early as 1896 Ad. Carnot (^Siir la mode de formation 

 des gites sédimentaires de phosphate de chaux. Compt. rend. Acad, des Sc. 123. 

 Paris, pp. 724 — 7:29) proved, that in general phosphorite and phosphate-chalk are 

 to be considered as shore- and lagoon-formations. 



") Charles W. Andrews. A Monograph of ChrisUnas Island (Indian Ocean). 

 London 1900, pp. 5289—291. 



