132 DISCOVERY REPORTS 



estimate. According to direct observations made during the course of the present work, httle more 

 than I sec. elapsed from the first appearance of the head above water to the submergence of the blow- 

 hole. This is astonishingly short and is rather shorter than an estimate of the time made by indirect 

 methods, according to which the blowing might perhaps take 3 sec, but even this is half the time allowed 

 by Racovitza. 



We are agreed with the view that the time taken over inspiration is shorter than the time taken over 

 expiration which immediately precedes it. Racovitza, however, maintains (p. 12) that 'La bosse de 

 I'event est toujours la seule partie qui apparait a ce moment sur I'eau', whereas numerous photographs 

 of living whales have shown other parts of the head and neck also above water. On p. 13 he notices 

 the neck bend, but for the intermediate dives he states that ' chez les Balenopteres la dorsale ne se 

 montre pas '. In the present series of observations, the dorsal fin showed above water after almost 

 every act of blowing seen (see p. 127). 



Whether it is possible to infer from the attitude of a whale whether it is making an intermediate dive 

 or whether it is sounding, may be questioned, as indeed may so many of Racovitza's assertions. 

 Andrews (1909), whose ideas are evidently modelled to a considerable extent upon Racovitza and 

 Millais, touches upon the subject but gives little that can be looked upon as corroborative evidence. 

 The posture of a whale diving at a steep angle is admittedly different from that of a whale swimming 

 horizontally, but whales have frequently been seen by the writer to dive at a steep angle during inter- 

 mediate dives. 



The view expressed by Andrews (1909) and Allen (1916) that the 'slick' left by the whales is due 

 to the counter-currents produced by the displaced water as the whale comes to the surface and with- 

 draws; or that it is ' incontestablement une couche de graisse extremement mince, qui s'etent a la 

 surface de I'eau et qui lui donne cet aspect bien connu du miroir ' (Racovitza, 1903, p. 15) ; or yet again, 

 the theories elaborated earlier leave out of account the fact that the patches often appear in series 

 when the whale does not break surface. They seem far more likely therefore to represent a gush of 

 water propelled upwards by the tail flukes. 



Respiratory rhythm 



Racovitza's estimate of the time taken over an intermediate dive ' plus ou moins longtemps, mais 

 sans jamais depasser un petit nombre de minutes' (p. 13), like his estimate of sounding 'rarement 

 inferieure a un quart d'heure' (p. 14) are far longer than our own. 



Owing to their limited number, our observations by no means exclude the probability that whales 

 can and do remain below for very much longer periods than we have been able to show. The estimates 

 of 15 min. made by Millais (loc. cit. p. 268) and of 23 min. by Andrews (1909, p. 225) are by no means 

 unreasonable and are to be expected from our data. But periods of over a quarter of an hour are certain 

 to be exceptional as compared to the frequency of sounding for shorter periods. 



In this our results confirm the observations of Allen (1904, p. 615) ' They rose to spout about once 

 in every 12 to 15 seconds with great regularity for perhaps twelve times, after which they dove for 

 a much longer stay of several minutes. The precise length of the longer periods was not accurately 

 determined, but could hardly have been more than five or ten minutes.' 



The mean of seven instances of such rhythm given in Table i shows the schools to have been blowing 

 at 16 sec. intervals seven to eight times and then to have been sounding for about 4 min. Individual 

 whales were blowing less often, however ; the figures gave an average of four to five times at intervals 

 of 26-27 sec. between each sounding. When feeding at the surface, or in flight, whales did not show 

 this rhythm and sounded less, so that the respiratory rhythm reflected to some extent their occupation. 

 Andrews (1909, p. 224) also has observed 'that Finbacks, when feeding, often rise to respire with 



