PROGRESSION ON AND IN THE WATER. 



101 



io discover the true action of the fins in question, but the 

 flight of the fish is so rapid that he utterly failed. He gives 

 it as his opinion that flight is performed in two ways, — first 

 by a spring or leap, and second by the spreading of the 

 pectoral fins, which are employed in propelling the fish in a 

 forward direction, either by flapping or by a motion analogous 

 to the skimming of swallows. He records the important fact, 

 that the flying- fish can change its course after leaving the 

 water, which satisfactorily proves that the fins are not simply 

 passive structures. Mr. Lord, of the Eoyal Artillery,^ thus 

 writes of those remarkable specimens of the finny tribe : — 

 " There is no sight more charming than the flight of a shoal 

 of flying-fish, as they shoot forth from the dark green wave 

 in a glittering throng, like silver birds in some gay fairy tale, 

 gleaming brightly in the sunshine, and then, with a mere 

 touch on the crest of the heaving billow, again flitting onward 

 reinvigorated and refreshed." 



Before proceeding to a consideration of the graceful and, 

 in some respects, mysterious evolutions of the denizens of the 

 air, and the far-stretching pinions by which they are pro- 

 duced, it may not be out of place to say a few words in re- 

 capitulation regarding the extent and nature of the surfaces 

 by which progression is secured on land and on or in the 

 water. This is the more necessary, as the travelling-surfaces 

 employed by animals in walking and swimming bear a cer- 

 tain, if not a fixed, relation to those employed by insects, bats, 

 and birds in flying. On looking back, we are at once struck 

 with the fact, remarkable in some respects, that the travelling- 

 surfaces, whether feet, flippers, fins, or pinions, are, as a rule, 

 increased in proportion to the tenuity of the medium on which 

 they are destined to operate. In the ox (fig. 18, p. 37) we 

 behold a ponderous body, slender extremities, and unusually 

 small feet. The feet are slightly expanded in the otter (fig. 1 2, 

 p. 34), and considerably so in the ornithorhynchus Tfig. 11, p. 

 34). The travelling-area is augmented in the seal (fig. 14, p. 

 34 ; fig. 36, p. 74), penguin (figs. 46 and 47, pp. 91 and 94), 

 sea-bear (fig. 37, p. 76), and turtle (fig. 44, p. 89). In the 

 triton (fig. 45, p. 89) a huge swimming-tail is added to the 

 1 Nature and Art, November 1866, p. 173. 



