348 Longevity of the Pcurot. 



convenient channel through which to send them down to 

 posterity. This channel is open in this Magazine ; through 

 which may the streams of science continue to flow on, still 

 fertilising as they flow ! 



The royal Psalmist has set down the average period of the 

 life of man at " threescore years and ten." But why should 

 we limit our knowledge to the duration of the life of man 

 alone, when 



" To all has Nature given a bound precise, 

 Of being and perfection ; and promulged 

 To every varying rank her varying laws" ? 



Mr. Waterton, your very valuable correspondent, and the 

 experienced naturalist, has not given us any account of the 

 length of the life of those species of birds whose biography 

 he has memorialised through the pages of this Magazine ; 

 which omission, I doubt not, has arisen from the great diffi- 

 culty there is in following any particular species of bird (or, 

 indeed, any animal, how familiar soever one may be with its 

 species), from the time of its infancy till old age puts a period 

 to its existence. 



I believe the natural duration of life in some of our domes- 

 ticated animals has been ascertained with tolerable accuracy. 

 The horse is said to live about 30 years ; the ox about the 

 same period ; the sheep about 20 years ; the hog about 20 

 years.* Of the last three species, the ox, the sheep, and the 

 hog, so few are allowed to reach even maturity, that I think 

 the natural duration of their lives is still involved in some un- 

 certainty. Naturalists, I believe, affirm, that the longer any 

 animal is in arriving at maturity, the longer is its period of 

 existence ; and, on the contrary, the sooner any animal arrives 

 at perfection, the sooner its course is finished. 



If this maxim holds good (and, upon a broad scale, it appears 

 very probable), I think, by ascertaining the time any animal 

 is in attaining its perfection, the period it endures in full ma- 

 turity, and the precise time of its beginning to decline, a 

 tolerably accurate estimate might be formed of the length of 

 the life of many species, of which we at present know nothing. 

 This might, in some degree, hold good in some of the lar^r 

 species of animals : but we must not take our examples from 

 animals in a state of confinement : they would mislead our 

 judgment, as many of them, from the privation of liberty, 

 from the artificial nature of their diet, the impurity of the 



* The Rev. G. White, in his Natural History of Selborne, mentions a 

 sow that produced young till she was fifteen years of age ; and then she 

 was fatted for bacon. 



