DEPARTMENT OF MARINE BIOLOGY. 189 



samples were not studied in so great detail. Mr. Bramlette resumed work on 

 the collection during the latter part of July. This work will constitute the 

 first critical study of the shoal-water bottom deposits in an embayment in a 

 tropical island and will be valuable for comparison with the studies made by 

 the Roj'-al Society coral-reef expedition to Funafuti, the studies made of the 

 deposits associated with the coral reef at Murray Island, Australia, and the 

 studies of the shoal-water deposits of the Bahamas and Florida. Accurate 

 knowledge of the shoal-water deposits in several parts of the tropical seas is now 

 becoming considerable. 



Bottom Samples prom the Bahamas and Florida. 



In consequence of interruptions due to the Great War and other causes, the 

 studies of the bottom samples I collected in association with the Department 

 of Marine Biology in the Bahamas and Florida betwen 1912 and 1915 suffered 

 postponement and but little was done on the samples between 1916 and the 

 summer of 1921, when the studies were resumed. An effort is being made to 

 complete certain supplemental studies and to present in form suitable for 

 publication the entire body of information. Considerable information on the 

 Bahamian and Floridian bottom deposits has been given in publication No. 213 

 of the Carnegie Institution, in other publications of the Institution, and else- 

 where, but the statements therein contained are only preliminary accounts of 

 the work. For instance, the results of only a small fraction of the mechanical 

 analyses have been printed. 



During the past year, Dr. M. I. Goldman, of the U. S. Geological Survey, 

 has completed an exhaustive study of the ingredients of a composite sample of 

 reef sand from behind Coconut Point reef, Andros Island, Bahamas. In 

 1921, Dr. Paul Bartsch collected for me an additional sample of calcium- 

 carbonate mud off the west side of Andros Island, while on an expedition under 

 the auspices of the Department of Marine Biology. This sample has been 

 elaborately studied in a number of different ways. A complete chemical 

 analysis and a special chemical analysis for organic carbon have been made by 

 Mr. E. T. Erickson in the Chemical Laboratory of the U. S. Geological Survey; 

 Professor Milton Whitney, chief of the Bureau of Soils, U. S. Department of 

 Agriculture, has supervised mechanical analyses and tests for colloidal 

 material by the amount of water- vapor absorbed; Dr. K. F. Kellerman of the 

 Bureau of Plant Industry, U. S. Department of Agriculture, has studied the 

 bacterial flora of this sample and has conducted experiments to ascertain if 

 certain bacteria will precipitate calcium carbonate when grown on no culture 

 medium except the bottom mud ; and I have devoted much time to a study of 

 the ingredients composing the sample. Dr. R. C. Wells, of the U. S. Geo- 

 logical Survey, is conducting a series of experiments on the cementation of 

 calcium-carbonate sands. Much other work has been done, but the details 

 will not be given here, enough having been said to indicate the progress made 

 in the investigations. 



The purpose of these investigations is to aid in understanding the origin, the 

 classification, and the lithification of limestones, and already important 

 results have been achieved. A point worth noting is that chemical analyses 

 and determinations of the percentages of material in the colloidal state have 

 recently been completed for about 60 deep-sea samples collected from the 



