THE PHYSIOLOGY OF DEEP-SEA LIFE. 



295 



mouth of the flask by a close-fitting india-rubber stopper. 

 The tube of the bulb has a lateral opening from an ingenious 

 sUde - valve between the bulb 

 and the flask. To the upper 

 part of the bidb is attached a 

 gas-tube with a double-ended 

 pipette, in which a vacuum is 

 formed by boiling out distilled 

 water from the bulb, closing the 

 upper end of the gas-tube, and 

 then making a connection with 

 the flask, which under the re- 

 lieved pressure will allow the 

 gas contained in the sea-water 

 to find its way into the gas- 

 tube. This is then sealed at 

 the other extremity, and the 

 contents analyzed on shore. 



Dr. Jacobsen concluded from 

 his analyses that the percent- 

 age of oxygen in sea-water was 

 practically invariable, the low- 

 est and highest percentages be- 

 ing 33.64 and 34.14. While 

 this is undoubtedly true for lim- 

 ited areas, the analyses by Dr. 

 J. Y. Buchanan of the " Challenger " show that, under varied 

 conditions of temperature, there was a somewhat wider range, 

 — between 33 and 35 per cent, in round numbers. The pro- 

 portion of oxygen being greatest on the surface, it begins at 

 once to diminish rapidly till it reaches more slowly a minimum, 

 at a depth of 300 fathoms ; and below this depth, its percent- 

 age remains constant. This does not quite agree with Dittmar's 

 results stated further on. 



The carbonic acid in the water was determined directly by dis- 

 tilling in a current of air conveying the gas, and collecting the 

 steam and carbonic acid in a vessel charged with baryta water. 

 By adding to the water to be tested a measured quantity of acid 



Fig. 19.3. — Bunsen's apparatus, modified 

 by Jacobsen and Behrens. 



