TITLES AND ABSTRACTS OF PAPERS 59 



Dr. A. M. Miller: There exists iu Bath County, Kentucky, a remarkable 

 deposit of oolitic carbonate of iron which is evidently a replaced Devonian 

 limestone, the oolitic structure therefore being a phenomenon accompanying 

 chemical replacement of an already consolidated lime sediment. 



Mr. T. W. Vaughan expressed pleasure in Professor Brown's presentation 

 lof the subject of the formation of oolites. The Bahamas and Florida offer an 

 ^advantageous field for study of the origin of oolites, as the formation of oolite 

 grains can be observed in the chemically precipitated calcareous muds so 

 abundant there. Mr. Vaughan said that as in his opinion the formation of 

 oolites from chemically precipitated calcium carbonate is established, atten- 

 tion should now be especially directed to the discovery of the agencies whereby 

 chemical precipitation is effected. Two classes of bacteria, the denitrifying 

 and sulphate-reducing, are such agents. Drew's work in the Bahamas showed 

 that there are off the western shore of Andros Island as many as 160,000,000 

 denitrifying bacteria to the cubic centimeter. It was mentioned that Dr. Carl 

 F. Kellerman, of the Bacteriological Laboratory of the United States Depart- 

 ment of Agriculture, had undertaken an investigation of the bacterial flora of 

 Great Salt Lake for the purpose of ascertaining what role bactei'ia may there 

 play in the precipitation of calcium carbonate, and that he had consented to 

 make additional researches on the bacteria of the muds and the waters of 

 southern Florida and the Bahamas. 



Further remarks were made by Dr. Chester A. Eeeds. 



PRECISE LEVELING AND THE PROBLEM OF COASTAL SUBSIDENCE 

 BY DOUGLAS W. JOHNSON 



(Abstract) 



Precise leveling recently completed in New Jersey and New York throws 

 some light on the question as to whether or not this part of the Atlantic coast 

 is undergoing progressive subsidence. The work in southern New Jersey shows 

 that there has been no differential tilting or warping of the coast during the 

 25 years from 1886 to 1911. Similar investigations in the vicinity of New 

 York city also show a total absence of any differential movement during 24 

 years, from 1887 to 1911. The surveys further show that the position of mean 

 sealevel has remained the same for 24 years at least. Taken together, these 

 facts prove remarkable stability of the portion of our coast supposed to show 

 the most pronounced evidences of continued subsidence and corroborate the 

 physiographic evidence of long-continued stability. 



Presented in full without notes. 



Discussion 



Prof. William H. Hobbs : The bearing of all earthquake study seems to 

 show that vertical movements of a coastline are Interrupted rather than 

 gradual and uniform. It is therefore quite possible that for a period of 25 

 years no movement would be registered, but might yet be followed by a very 

 considerable adjustment of level in the succeeding years. 



