368 DISCOVERY REPORTS 



account so far has been taken of the possibility of a much greater elasticity in whales' 

 lungs than in those of man. Unfortunately no figures are available to show the maximum 

 internal volume of the thorax in the particular whale under consideration, but in a Fin 

 whale measured by myself in South Georgia, length 22 m., the volume of the thorax 

 was 8 cm. after death, when probably it was not fully expanded. Of this the heart and 

 blood vessels occupied approximately 0-5 cm., so that there were at least 7-5 cm. of 

 space available for the accommodation of the lungs. If the vital capacity is taken to be 

 7 cm., the whale could remain submerged for 39 min. It would be unprofitable to try 

 to assess more accurately the probable vital capacity of the Blue whale originally con- 

 sidered; but these figures indicate that a submersion period of 17-30 min. for a whale 

 at rest is a very conservative estimate. 



DIVING 



Depth and duration. What the energy requirements of an active whale would be 

 while submerged it is hard to say. But there is reason to suppose that during long sub- 

 mergence whales do not move rapidly since they frequently reappear after a quarter of 

 an hour close to the spot at which they dived. Little reliable information is available 

 on the normal period of diving of Blue whales. Most observations have been taken 

 when the whale either is being chased or has already been harpooned. A whale tends 

 to hide beneath the surface when chased and the time of submergence is 10 min. or 

 more. A harpooned whale will stay down as long as 25 min., returning to the surface 

 with a rush, and will not again remain submerged for a long period until it has had an 

 opportunity to ventilate the lungs thoroughly. I have noticed that estimates of the 

 time of submergence of whales during the chase are liable to be faulty and greatly 

 exaggerated owing to the suspense which prevails. I have gathered from conversations 

 with Norwegian gunners that the average time of submergence of a Blue whale which 

 is not alarmed is about 10 min. On being chased or harpooned the dive may last as 

 long as half an hour. 



The depth to which whales dive is a matter of the greatest interest physiologically, 

 since the pressure on the animal becomes of significance in all considerations of the 

 whale's respiration. The external hydrostatic pressure becomes communicated to the 

 lungs and the air in them, so that pressure afl'ects the most vital processes. There have 

 been many wild estimates of the depth to which whales can dive ; but W, Scoresby jun. 

 (1820) has given a conservative account of the behaviour of the Greenland Right whale. 

 "When fish have been struck by myself, I have on different occasions estimated their 

 rate of descent. For the first 300 fathoms the average velocity was usually after the rate 

 of 8 to 10 miles per hour. In one instance the third line of 120 fathoms was run out in 

 61 sec, that is at the rate of 8^ English miles or 7^ nautical miles per hour.... The 

 average stay under water of a wounded whale, which descends steadily when struck, 

 according to the most usual conduct of the animal is about 30 min. But in shallow water, 

 I have been informed, it has sometimes been known to remain an hour and a half at the 

 bottom after being struck and yet has returned to the surface aUve. . . .The remarkable 



