ll>8 THE REASON WHY" : 



With such accoutrements, with such a form, 



Much like a porptrise, just before a storm." CHURCHILL. 



594. This is th 3 mode of swimming in all the whale tribe ; and it is easy to see, 

 from the formation of the tail, the most powerful organ of motion they possess, this 

 must be the case. Their action, like that of land mammalia, is vertical, as distin- 

 guished from the horizontal one of fishes. Their tails strike upward and down- 

 ward, and those of fishes laterally. The resistance to the stroke upwards is less 

 than the stroke downwards, because the pressure of Ihe water increases with ita 

 depth : and thus, when cetaceous animals make great exertions in swimming, they 

 always have a tendency to "roll." 



595. Wliy is the porpoise (or porcpesse) so named ? 



The name, signifying sea-hog, was given to this animal from a 

 fancied resemblance to the hog in the character of its head, and in 

 its habits of rooting for food. 



596. Why is its appearance at sea in numerous packs thought 

 by mariners to forewarn a storm ? 



Because it has been frequently found that previous to rough 

 weather, when few sea animals can procure food, an instinct has 

 led porpoises to take advantage of the opportunity afforded by the 

 calm, and so to provide for a period of deprivation. 



597. Why have whales, dolphins, &c., the flat surface of their 

 tails placed horizontally, instead of vertically ? 



This difference to the ordinary fishes is to favour the important 

 function of respiration ; for these inhabitants of the sea must rise 

 to the surface to breathe the air, and their tails are thus directed 

 to enable them to elevate their heads above water. 



MISCELLANEOUS. 



598. Why is the omnivorous character of man beneficial to 

 the lower terrestrial creation? 



Because, by his appetite for various kinds of flesh, he is incited 

 to subdue and utilize every kind of animal substance. This tends 



