GEOLOGY. 373 



brought up partly to call the attention of geologists to a method of 

 research which promises important results. As indicating an extension 

 of such investigations, it will be said that arrangements have been made 

 with the geologists associated or cooperating with the Coastal Plain 

 investigations of the U. S. Geological Survey to make studies similar 

 to those mentioned for the continental shelf along the entire Atlantic 

 and Gulf borders of the United States and for most of Central America. 

 References to such studies in the area off the Florida coral-reef tract 

 will be found on pp. 236-237 of this Year Book. 



With regard to the locus of the hving reefs in the West Indies, it 

 will be said that they have grown upon these terraces either during 

 or subsequent to submergence, and conform to the principles found to 

 govern their development on Mosquito and Campeche Banks, off 

 Honduras, and in Florida.^ (See pp. 233-238 of this Year Book.) 



Attention has also been paid to the causes producing changes in 

 position of strand line in Recent geologic time. As the subject is a 

 vast and complicated one, although the body of information on Pleisto- 

 cene and Recent strand-line movements is rapidly increasing, all that 

 should at present be expected in interpretation is the formulation of 

 working hypotheses. Professor Joseph Barrell, of Yale University, has 

 cooperated by writing an article entitled ''Factors in movements of the 

 strand line and their results in the Pleistocene and Post-Pleistocene,"^ 

 and Professor W. J. Humphreys, of the U. S. Weather Bureau, has 

 reconsidered the subject "Changes of sea-level due to changes of ocean 

 volume."^ The continued critical investigation of shore-line phenom- 

 ena, it is hoped, will render possible the discrimination of results which 

 may be due to local causes from those which may be due to general 

 causes, and ultimately lead to the discovery of whatever general causes 

 may have been operative, and should they be multiple, supply a basis 

 for the evaluation of the effects ascribable to each. 



iR. T. Hill, although he did not elaborate the theme, was perhaps the first to recognize the rela- 

 tions living coral reefs bear to submerged terrace surfaces. In his "Geology and physical 

 geography of Jamaica," Bull. Mus. Comp. Zool., vol. 34, pp. 99-100, 1899, he says, after describing 

 the elevated reefs: "That Jamaica was once a more extensive land than now, with benched and 

 toiTaced margins which were submerged by subsidence, is shown not only by the adjacent sub- 

 marine configuration but by the elevated reefs themselves, such as that at Barbican, which can 

 be seen to be clearly deposited upon a surface horizontally eroded across the vertical structure of 

 the old Blue Mountain Series. Similar submerged plains are now occupied by the growing reefs 

 around the island." An article by E. C. Andrews, entitled "Relations of coral reefs to crust 

 movements in the Fiji Islands" (Amer. Journ. Sci., 4th ser., vol. 41, pp. 135-141, 1916), should 

 be read in this connection. 



^Published in full, Amer. Journ. Sci., 4th ser., vol. 40, pp. 1-22, July 1915. The paper was 

 read before the Geological Society of Washington, March 24, 1915, and an abstract, entitled 

 "Factors in movements of the strand line," with discussion of it, appeared in Journ. Wash. Acad. 

 Sci., vol. 5, pp. 413-420, 444-447, 1915. 



^Journ. Wash. Acad. Sci., vol. 5, pp. 445-446, 1915. 



