140 CARNEGIE INSTITUTION OF WASHINGTON. 



(Year Book No. 14, p. 154), attention has been concentrated upon 

 two points in particular: (1) the appearance of CaCOa in forms other 

 than calcite and the conditions under which such other forms may 

 appear and persist; (2) the solubiUty of calcium carbonate under 

 various conditions, with particular attention perhaps to its concentra- 

 tion in and eventual deposition from sea-water. Of the forms other 

 than calcite the only one of geologic importance at present is aragonite; 

 but, by reason of the fact that aragonite is an unstable form, it is not 

 feasible to specify the conditions which really detennine its appearance. 

 Organic agencies are doubtless responsible for a great part of the 

 aragonite found in nature, but there is no question that it may some- 

 times be precipitated in other ways, either at the higher temperatures 

 or in the presence of certain salts. This work, therefore, though it has 

 cleared up a number of points which hitherto have been obscure, has 

 not yet enabled us to make definite, positive inferences from the associa- 

 tion in which aragonite is found in particular localities. 



As a result of the recalculation of the solubility data, the solubiUty- 

 product constant of calcite can now be regarded as established with 

 sufficient accuracy, and it is now possible in consequence to compute 

 the solubiUty of calcite under any conditions ordinarily met with in 

 nature. Comparison of the results of such computations with the 

 available analytical data has led us to the behef that the warm portions 

 of the ocean-water are substantially saturated with calcite, a belief 

 which carries with it important implications. Of these, two may be 

 mentioned, namely, (1) that, wherever the sea-water is saturated with 

 calcite its degree of alkalinity is fixed thereby, and (2) that abstraction 

 of CO2 from the water, by whatever agency achieved (e. g., by a slight 

 diminution in the CO2 content of the superjacent air), must result in 

 the precipitation of a definite quantity of CaCOs. It also follows di- 

 rectly that such water would be a very efficient regulator of the 

 amount of CO2 in the atmosphere. The complete validity of this 

 conclusion ought not, perhaps, to be regarded as definitely established 

 until more accurate determinations have been made upon sea-water 

 from a wide range of locaUties; the only data now available were 

 obtained from a somewhat restricted region and their accuracy leaves 

 much to be desired. Particularly is this true with regard to the 

 various existing determinations of CO2, bound and free, when ex- 

 amined in the light of the conditions of equilibrimn involved in such 

 determinations. But these errors are no longer unavoidable, and it is 

 greatly to be hoped that a systematic investigation of the ocean-waters 

 from this viewpoint may be undertaken in the near future. Such an 

 investigation is highly desirable by reason of its bearing upon many 

 biological questions as well as upon the important geologic problems 

 which we have considered. 



