THE PRECIPITATION OF CALCIUM CARBONATE IN THE SEA. 493 



elaborate apparatus that would be necessary in order to estimate 

 chemically the amount of denitrification in cultures, it was only 

 possible to compare the rate of denitrification in different cultures by 

 noting the time taken for the first appearance of the Nitrite reaction, 

 and the time taken for all trace of Nitrite or Nitrate to disappear. It 

 seems that the rate of denitrification in culture media inoculated with 

 equal volumes of samples of sea-water must be a function of the 

 number of bacteria in the sample, the temperature at which the 

 cultures are grown, and the specific power of denitrification of the 

 individual species of bacteria. Considering the rapid multiplication 

 of bacteria when the food supply is plentiful, up to a maximum deter- 

 mined chiefly by the accumulation of the waste products of their own 

 metabolism, it appears that the factor of the number of bacteria in 

 the sample may be neglected within the limits of these experiments. 

 For example, the number of bacteria in 1000 c.c. of Gran's medium at 

 the end of twenty-four hours would probably be much the same 

 whether it were inoculated from a sample containing 8 or 16 bacteria 

 per 1 c.c, similarly it was a matter of experience that the first trace 

 of Nitrite formation was observable at about the same time, whether 

 5 or 10 c.c. of a given sample had been used for inoculation. 



Consequently it would appear that for purposes of comparison, and 

 within the limits of the experiments described, if the temperature be 

 the same for the cultures compared, the rate of denitrification is a 

 measure of the specific denitrifying power of the particular species of 

 bacteria. 



In the work on the bacterial precipitation of Calcium carbonate, the 

 precipitate, which was often so fine as to tend to remain in suspension, 

 was usually obtained by centrifugalization. It was either preserved 

 in small bottles with some of the culture fluid, or else washed first 

 with distilled water and then with absolute alcohol, and finally allowed 

 to dry. These precipitates were sent to Dr. F. Wright of the Carnegie 

 Geophysical Laboratory at Washington, who with great kindness 

 reported on their mineralogical properties. 



THE INVESTIGATION OF SAMPLES OF SEA-W^ATER 

 TAKEN OFF PORT ROYAL, JAMAICA. 



The work at Port Royal was done in May, 1911, but was of a very 

 preliminary nature. It was necessary to depend on a sailing-boat for 

 obtaining the samples, but owing to the remarkable regularity with 

 which an on-shore wind springs up every morning but little difficulty 



