On the Precipitation of Calcium Carbonate. 



37 



that B. calcis will grow slowly at 15° C, but that growth is totally inhibited 

 at 10° C. It would thus seem that the observed distribution of the bacteria 

 agrees fairly with what might be expected from the temperature conditions. 



As regards these observations on the occurrence of bacteria in small 

 numbers at depths below 350 fathoms, the possibility of experimental error 

 must be considered; a leakage into the water-bottle of 0.25 c.c, as it was 

 being hauled up through the last 300 fathoms, would account for the number 

 found, and there are also many possible sources of error in the process of 

 siphoning ofif the sample and making the cultures where a permanent labor- 

 atory is not available. It is possible that the water below 350 fathoms was 

 really sterile, though if so the constancy of the results obtained is curious if 

 ascribed to experimental error. In any case, the small number of bacteria 

 found at depths below 350 fathoms can play no part in the metabolism of 

 the sea, since it has been shown that B. calcis is incapable of growth at the 

 temperatures obtaining at these depths. 



The much greater abundance of bacteria in the surface waters of the 

 Tongue of the Ocean than in the waters around Tortugas may perhaps be 

 accounted for by the fact that in the Tongue of the Ocean by far the greater 

 part of the surface water must flow over the immense chalky mud fiats and 

 shallows which bound it in most directions and, as will presently be shown, 

 these mud flats are phenomenally rich in bacteria and are probably still 

 being deposited by bacterial agency. 



HYDROGRAPHIC OBSERVATIONS IN THE TONGUE OF THE OCEAN. 



The samples of water taken for hydrographic investigations were 

 analyzed by Mr. D. J. Matthews at Plymouth. With great kindness he 

 calculated the results, and from his notes the following observations and 

 conclusions are drawn. 



The samples were analyzed for salinity in comparison with the standard 

 sea-water supplied by the Central Laboratory of the Conseil International 

 pour I'Exploration de la Mer, and hence the results are strictly comparable 

 with all other analyses published under the auspices of this International 

 Council. The following results were obtained: 



Note. — The original surface sample was lost, owing to breakage of the bottle in transit to England. The 

 analysis was made on a sample taken 3 days later at the same spot. 



In this table Cl " 00 means the weight of chlorine in grams found in 1,000 grams of sea -water. S '00 means 

 the salinity, or total weight of salt in grams found in 1,000 grams of sea-water, aa represents the specific 

 gravity of the sample at 0° C, and at represents the specific gravity of the sample at the temperature I at which 

 it was collected, with no correction for pressure. 



