64 



If our earth be trodden at present by no mammal so 

 large as the Mastodon of North America, nor by any bird 

 so huge as the Deinornis or moa of New Zealand, their dis- 

 appearance is obviously so recent, that there is little difficulty 

 in supposing that the extirpation of such species may be 

 owing to the hand of man. Indeed the various species of the 

 animal kingdom seem to be in danger of violent extinction in 

 direct proportion to their size. The increase of this renders 

 them in general less ferocious compared with other species. 

 A porpoise, that is, the least of known Cetacea, is exceedingly 

 voracious; but a sperm whale (whether Catodon or JEuphysetes) 

 which is nearly, as we have seen, the same as a porpoise in 

 all the essentials of its structure, is rendered comparatively 

 harmless by the want of teeth in the upper jaw. This defi- 

 ciency perhaps was necessary to aid its bulky stores of 

 spermaceti in balancing the specific gravity of its massive 

 skull. Kight whales are in like manner rendered mild 

 and timid by an entire want of teeth, although the weight of 

 of their skull is also relieved by the peculiar way in which the 

 quantity of bone in it is reduced.* Thus it is that immense 

 size is not ordinarily the characteristic of a beast of prey, and 

 that the largest Cetacea feed only on minute mollusca. As for 

 the immense size of Cetacea, it evidently proceeds from their 

 buoyancy in the medium in which they live, and their being 

 enabled thus to counteract the force of gravity. 



Sperm whales are found to inhabit warmer seas than true 

 whales, and are brought more within the reach of those 

 persons whose love of destruction is attracted by their size and 

 timidity, and whose love of money is excited by the value of 

 their oil. Many whalers of late have declared that the number 

 of young sperm calves annually killed is so great as to threaten 

 the speedy annihilation of this kind of whale. With less 

 motives for killing off the species, thus certainly within our 

 own times has man wantonly extinguished the Nestor pro- 



* It is for a similar reason that so many dolphins and other Cetacea have 

 the branches of their under jaw hollow, while the symphysis is very short. 



