GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 251 



eea and that concentration by evaporation is taking place. As the results of these 

 lines of inquiry are so positive, the formation of lagoons by submarine solution may 

 be definitely eliminated from consideration. 



Since the publication of this statement other investigators have 

 made important contributions to this subject, noteworthy among 

 whom are John Johnston, H. E. Merwin, and E. D. Williamson, of 

 the Geophysical Laboratory of the Carnegie Institution of Wash- 

 ington, and Roger C. Wells, of the United States Geological Survey. 

 Wells says : 1 



In other words, sea water [from the Florida reef] appears to contain so much car- 

 bonate that in contact with the atmosphere at 1° C. it neither has nor acquires an 

 appreciable solvent action on calcite. 



As I have considered the subject in detail in my paper on the 

 Murray Island bottom-samples 2 and in a paper on "Chemical and 

 organic deposits of the sea" 3 I will merely say that sea water in 

 shoal-water areas within the Tropics can not dissolve calcium car- 

 bonate, and that lagoon channels and atoll lagoons are not formed 

 by solution, but are flattish areas more or less completely inclosed by 

 built-up walls. 



As lagoons are areas of sedimentation and not of removal of 

 material, their formation by submarine scour may also be discarded. 



EFFECTS OF WIND-INDUCED AND OTHER CURRENTS IN SHAPING CORAL REEFS. 



This is an old topic; in fact, considerable bibliographic work 

 would be needed to ascertain the names of all the investigators who 

 have contributed to it and who deserve mention. That Darwin at 

 least had an adumbration of the importance of these agents is indi- 

 cated by his statement regarding Keeling atoll: 4 



That they [the waves] beat against it in the same peculiar manner in which the swell 

 from windward now obliquely curls round the margin of the reef, was evident from the 

 conglomerate having been worn in to a point projecting from the beach in a similarly 

 oblique manner. 



Among recent investigators Hedley and Griffith Taylor, as noted 

 on page 245, Wood Jones, 5 and I, in a number of my papers, two 

 of which are cited below, 6 have devoted attention to this subject. 

 During the field season of 1914 I had numbers of Ekman meter 

 current-measurements made around Tortugas and at other places 

 along the' Florida reef tract. The measurements to a certain degree 



1 Wells, R. C, The solubility of calcite in sea water in contact with the atmosphere, and its variation 

 with temperature, Carnegie Inst. Washington Pub. 213, pp. 316-318, 1918. 



2 Carnegie Inst. Washington Pub. 213, pp. 265-268, 1917. 

 » Geol. Soc. Amer. Bull., vol. 28, pp. 933-944, 1918. 



* Structure and distribution of coral reefs, ed. 3, p. 22, 1889. 



5 Coral and atolls, pp. 253-261, 1910. 



6 The building of the Marquesas and Tortugas atolls and a sketch of the geologic history of the Florida reef 

 tract, Carnegie Inst. Washington Pub. 182, pp. 55-67, 1914; Sketch of geologic history of the Florida coral- 

 reef tract and comparisons with other coral-reef areas, Washington Acad. Sci. Journ., vol. 4, pp. 26-34, 

 1914. 



