and the Evidence of the Funafuti Borings. 89 



high and low tide level. Dr. Cullis also draw? attention 

 to the mineralogical change from aragonite to calcite in the 

 materials of the upper part of the hore cores. In the top 

 cores aragonite is freely represented in the corals, and certain 

 other organisms, and as chemically deposited carbonate. With 

 this occurs calcite in the form of organisms and as chemically 

 deposited material. At about 100 ft. in depth it is noted that 

 less aragonite and more calcite are represented due partly to the 

 deposition of calcite instead of aragonite and partly to conver- 

 sion of aragonite to calcite. Below 100 ft. this mineralogical 

 change is more noticeable, and at 150 ft. practically all aragon- 

 ite has gone, the lowest depth at which it has been recog- 

 nised being 220 feet. 



This mineralogical change involving a change in the appear- 

 ance of the rock cores, it will be noted, is gradual and not 

 abrupt, but it is probably responsible for certain erroneous 

 conclusions to be mentioned below. Summarizing the evi- 

 dence of the organisms and of the textural features of the main 

 boring at .Funafuti it may be stated that all the organisms 

 belong to recent forms, most of the species are still living, 

 nearly all are forms which only live in the shallow water of 

 the reef and lagoon, many of the reef-forming corals in all 

 parts of the bore, including the lowest cores, occur upright, 

 in the position of growth, no deep-water types of organisms 

 were found and no Tertiary forms. 



No evidence of coral talus and no true sign of bedding was 

 noticeable although carefully sought for. Stalagmitic linings 

 to cavities in the coral limestone, such as might be expected to 

 be deposited in very shallow or tidal waters, occurred at inter- 

 vals down to the bottom cores, while the change from araa;on- 

 ite to calcite in the material of the core involving a change in 

 the appearance of the rock occurred gradually between the 

 depths of 100-150 ft., and was complete at a depth of 220 ft. 



It will be noted that the above facts are completely at vari- 

 ance with the view expressed by Agassiz* in his paper on the 

 Coral Reefs of the Tropical Pacific. Therein he remarked as 

 follows : "The boring at Funafuti reached 1 111 ft. It passed 

 at first through the modern reef rock material and below 

 that must have, judging by analogy, penetrated either an un- 

 derlying mass of Tertiary limestone or have passed through the 

 mass of modern reef rock forming the outer talus of the atoll 

 of Funafuti." 



Prof. Dalyf in his paper on the glacial control theory of 

 Coral Reefs after discussing Von Lendenfeld's view of the 

 development of an atoll by centrifugal displacement of the 

 outcrop as sinking progresses, states: "If Von Lendenfeld's 



*Mem. Mus. Comp. Zool., Harvard, xxviii, pp. 21, 22, 1903. 

 fDaly, Proc. Arner. Acad. Sci., li, p. 247, 1915. 



