BOTTOM SAMPLES, MURRAY ISLAND, THE BAHAMAS, AND FLORIDA. 267 



extent of combined C0 2 — are altogether untrustworthy, since the results 

 depend on the amount of indicator added and upon other factors which have 

 not been adequately controlled." The inference from this statement is 

 that in the writers' opinion the method used by Dole in his work 1 is subject 

 to question. However that may be, geologically speaking the results of Dole 

 and of Johnston and Williamson are identical. 



Johnston and Williamson have paid particular attention to the solu- 

 bility-product constant [Ca ++ ] [C0 3 = ], the concentration of H 2 C0 3 , the 

 effect of temperature on H 2 C0 3 concentration, and the relation of the solu- 

 bility-product constant to rise in temperature. Two quotations from this 

 paper follow: 



'Now it is possible that calcium carbonate may through the intervention of 

 biologic agencies be precipitated within a medium which is not saturated with it, 

 yet a permanent deposit can hardly result unless either (1) the solution in contact 

 with it is saturated with respect to CaC0 3 , or (2) the precipitated carbonate is pro- 

 tected from the solution by an organic tissue or otherwise, or (3) that the process of 

 deposition is rapid, in water circulating very slowly or not at all, under which con- 

 conditions re-solution by diffusion is very slow. The fact therefore that permanent 

 deposits are being formed in many regions of the sea is of itself good evidence 

 that the water in those regions is substantially saturated with respect to CaC0 3 . 

 Indeed recent experiments of A. G. Mayer 2 show that the sea-water about the 

 coast of Florida is substantially saturated, for shells exposed to it for a year lost no 

 significant weight. Moreover, the investigations of T. W. Vaughan 3 on coral 

 reefs 'show that submarine solution is not effective there [about Florida], as all the 

 bays, sounds, and lagoons are being filled with sediment,' a conclusion which accords 

 'with the conclusions reached by numerous investigators in the Pacific, which are 

 that the more or less continuous walls inclosing lagoons have been formed by con- 

 structional geologic processes and that lagoon channels and atoll lagoons are not due 

 to submarine solution.' We believe therefore that the surface layers of the ocean, 

 except in the Polar regions, and within currents of cold water — in other words, the 

 warmer portions of the ocean — are substantially saturated with CaC0 3 ; but the 

 truth of this belief can not be regarded as established until trustworthy determina- 

 tions of the several quantities concerned have been made." 



They summarize their conclusions as follows: 



"In discussions of the mode of deposition of calcium carbonate there is a point 

 which has not received adequate recognition; namely, the concentration of calcium 

 relative to the limiting saturation concentration of calcium carbonate under the 

 particular conditions, or, in other words, the relative degree of saturation of calcium 

 carbonate, and its local variation, throughout the ocean. The neglect of this 

 important point is without doubt due to the erroneous and misleading statements 

 as to the solubility of CaC0 3 which have been prevalent. Its solubility under 

 specified conditions can now be calculated with the requisite accuracy; it is affected 

 materially by variations of temperature and of concentration of free C0 2 such as 

 occur in nature. For example, a change in the proportion of C0 2 in the air from 



■Carnegie Inst. Wash. Pub. 182, p. 71, 1914. 

 •Mayer, A. G., Proc. Nat. Acad., 2, 28, 1916. 



'Vaughan, T. W, Am. Jour. Sci. 41, 133, 1916; see also his earlier papers, especially in the publications of 

 the Carnegie Institution of Washington. 



