226 WHALES AND DOLPHINS 



destination so straight is the course they steer, and it is possible 

 that they have. ' Fins,' as they are commonly called for 

 short, on the occasions when they are met with singly or only 

 a few together are usually feeding, and they are then hunted 

 in much the same way as the Blue Whale. But when a 

 ' school ' is encountered, the procedure differs. A whaler 

 with high speed is necessary to capture the fast-moving Fins 

 for they have literally to be run down. The excitement of 

 chasing this animal is much greater than any provided by 

 the humdrum creep after Blues." 



It is difficult for the unskilled. to distinguish the different 

 species of Rorquals by their " blow ", the variations appre- 

 ciated by the whalers being generally of degree rather than of 

 essential difference in form. In all Rorquals the " blow " is 

 vertically upwards and, in its early stages, shaped like an 

 attenuated inverted cone. Atmospheric conditions, of course, 

 alter the permanence of the effect ; it is most clearly seen in 

 cold weather, and soonest dissipated when it is windy. It 

 should not be thought that the whale blows or spouts water 

 through the blowhole. Moisture-charged breath is vigorously 

 ejected under pressure from the lungs and expands as it reaches 

 the air. This expansion causes a fall of temperature, which 

 brings about a condensation of the water vapour in the expired 

 breath in the form of a visible cloud. 



The progression of the whale through the water is punctuated 

 by the necessity to come up for fresh air at intervals. Usually 

 a series of shallow dives are succeeded by a deeper one of 

 longer duration, when the animal is said to " sound " The 

 shallow dives are in more or less rapid succession and vary in 

 number ; in a recorded instance the whale dived four times 

 at 15-second intervals. During the " blows " between shallow 

 dives the air in the lungs is thoroughly refreshed, and then 

 the animal, arching its body and taking a final inspiration, 

 swims steeply downwards. It remains underneath for a time 

 which may be anything from about 4 to 15 minutes ; the 

 maximum time of remaining under water is not known, but 

 it is probably about half an hour. When the whale dives its 

 body is rounded into an arc, so that the observer sees in 

 succession head and shoulders, back and dorsal fin, then tail 

 appear and disappear, but in the Fin Whale the tail flukes 



