On the Precipitation of Calcium Carbonate. 



35 



From these counts it is apparent that the number of bacteria falls off at 

 some point between 200 and 400 fathoms. 



The second station was worked on May 1 1 at a point 14 miles due east 

 of Golding Cay. The sea was calm at first, and the wind ENE., force i, 

 but later in the day a heavy swell set in and the wind freshened to about 

 force 4; eventually the weather became so bad that it was impossible to 

 work, and the station had to be abandoned before it was completed. 

 Bottom was sounded at 890 fathoms, but there was some stray on the wire, 

 so that the true depth was probably about 825 fathoms, as shown by the 

 chart. The bottom consisted of fine white calcareous ooze; no remains of 

 pteropods were seen, but some globigerina shells were present. The follow- 

 ing temperatures were recorded : 



Samples down to a depth of 200 fathoms were diluted i in 100 with 

 sterilized sea-water before plating. The following results were obtained 

 after 48 hours' growth: 



Depth. 



No. of colonies 



developing 



from I CO. of 



sample. 



Fmi. 



Surface | 16,200 



10 13,100 



50 14,000 



100 14,000 



200 15,000 



300 14 



400 12 



The figures given represent the mean of the number of colonies develop- 

 ing in the two plates that were made from each sample. It is here apparent 

 that the number of bacteria per i c.c. falls off very rapidly between 200 and 

 300 fathoms. 



