52 Papers from the Marine Biological Laboratory at Tortugas. 



or sodium is at first of gelatinous consistency and later aggregates into 

 spherulites. 



In 1903, G. Linck published, in an article entitled "Die Bildung der 

 Oolithe und Rogensteine,"^ accounts of a series of important experiments 

 he conducted on the precipitation of calcium carbonate from sea-water by 

 the addition of alkaline carbonates, and in 1909 another contribution from 

 him, "Ueber die Bildung der Oolithe und Rogensteine, " appeared in the 

 Jenaische Zeitschrift fur Wissenschaft, vol. 45, pp. 267-278. According 

 to Linck's experiments calcium carbonate precipitated from sea-water at 

 a temperature of 17° C. to 40° C, by adding an alkaline carbonate, is 

 aragonite and aggregates into spherulites, the diameters of which range 

 from 0.02 to 0.2 mm. Murray and Irvine have shown that calcium car- 

 bonate precipitated from sea-water by an alkaline carbonate at a tempera- 

 ture of 34° F. is calcite, at 47° F. is a mixture of calcite and aragonite, at 

 80° and over is aragonite.- 



Drew in 1912 published the following statement regarding the calcium 

 carbonate precipitated^ in a culture from a sample of water from Marquesas 

 Lagoon : 



To such a culture a trace of very finely powdered hydrated calcium sulphate was added. 

 This resulted in the formation of a precipitate, which, on microscopical examination, could 

 be seen to consist of finely laminated concretions, some of which appeared to have a particle 

 of calcium sulphate or sand as a nucleus. The concretions were soluble in dilute hydro- 

 chloric acid with evolution of carbon dioxide. These concretions bear a resemblance to 

 those of some oolitic limestones, and the experiment suggests the manner in which such 

 oolites may have been formed. 



These references, although they lay no claim to completeness, are clear 

 evidence that calcium carbonate, particularly aragonite, when precipitated 

 from a water-soluble calcium salt by the addition of an alkaline carbonate, 

 is at first of gelatinous consistency and later aggregates into spherulites.^ 



As I did not observe oolite grains in the muds when collected in the 

 field, I was led to the opinion that oolitization was the result of secondary 

 changes after precipitation and directed my attention to ascertaining if 

 such supposed changes were taking place. ^ 



Bahaman shoal-water bottom muds were collected through South Bight 

 and off the west shore of Andros; and other samples were collected in 

 Florida. As has been stated, these flocculent oozes when collected were not 

 observed to contain oolite grains; howe\-er, such grains may have been 

 present and may have escaped attention. All the Bahaman muds when 

 examined at the end of November did contain oolite. Besides oolite grains, 

 finely divided particles less than o.ooi mm. in diameter, some fragmental 



> Neues Jahrb. fur Min. Beilage. Bd. l6, pp. 49S-SI3- 



2 Proc. Roy. Sci. Edin., vol. 17, pp. 79-109. 1890. 



' Carnegie Institution of Washington, Year Book No. 10, p. 141. 1911. 



* Without making a special diversion to go into the subject, it may be mentioned that spheruhtes or oohtes 

 of calcium malate and calcium phosphate are well known, and that the occurrence of spherulites of barium car- 

 bonate and strontium carbonate have been recorded. It is therefore established that a number of salts of the 

 calcium group of elements may assume a spherulitic form. 



'" Carnegie Institution of Washington, Year Book No. 11, pp. IS5, I37, 158. 1913. 



