182 



CARNEGIE INSTITUTION OF WASHINGTON. 



coruls need only two additional lines of inquiry in order to be adequately 

 known. One of these is to obtain more accurate information on the tem- 

 perature gradient with increasing depth of water, a subject on which some 

 data are available but have not been tabulated. The other line of inquiry 

 is to ascertain the upper and lower limits of temperature at which corals will 

 take food. 



A few samples of water were collected in 1912 for salinity determination, 

 and, by an arrangement with Mr. George C. Short, samples of water were 

 collected in Fort Jefferson moat during and after heavy rains in January 

 and February 1913. The latter samples are intended to indicate the 

 amount of dilution to which the water in the moat is subject. Through an 

 arrangement effected between the Laboratory of Marine Biology and the 

 U. S. Geological Survey, Mr. R. B. Dole, of the latter organization, under- 

 took during June the examination of a series of water samples collected at 

 the Tortugas. He determined the salinity of the samples collected by Mr. 

 Short and of a set of samples collected twice daily, at ebbing and flowing tide, 

 for nearly a lunar period, in Southwest Channel off the southern end of 

 White Shoal. Other samples were also examined. 



The following data furnished by Mr. Dole are to be considered in this 

 connection: 



Salinily of Tortugas waters, as determined by R. B. Dole* 



*A more comprehensive statement is made by Mr. Dole in his article "Some chemical character- 

 istics of sea-water at Tortugas, Florida," Carn. Inst. Wash. Pub. No. 182. 



The water specimens collected in July 1912 were titrated, through the 

 kind offices of Mr. Drew, by Mr. D. J. Matthews, at the Plymouth, England, 

 marine laboratory, and gave the following results : 



Salinity of Tortugas waters, as determined by D. J. Matthews. 



More information on saUnity along the line of the reefs is greatly desired, 

 and it is hoped this may be procured. Experimental investigation of the 

 degrees of salinity, the maximum and minimum which the different species 

 of corals will endure, remains to be made. 



