4* LETTER X. 



and agility, and all in dexterity. In all these par- 

 ticulars, however, habit has a great and remarkable 

 influence. Constant exercise is requisite to invigo- 

 rate the human body ; and the strength of man is very 

 considerable, and indeed almost incredible, when 

 thoroughly matured by practice. We are assured, 

 that the porters of Constantinople can carry burdens 

 x>f nine hundred pounds weight ; and M. Desaguliert> 

 informs us of a man, 'who, standing in an upright pos- 

 tUTe, by distributing the weight in such a manner that 

 $very part might bear its share, supported the inere- 

 iible weight of two thousand pounds. 



Men who are accustomed to running, can in length 

 of time outstrip horses. The royal messengers of 

 Ispahan, who arc runners by profession, can go above 

 an hundred miles in fourteen or fifteen hours ; and 

 seme travellers tell us, that savages, who hunt the 

 elk, pursue with such speed and perseverance that ani- 

 mal, which is as fleet as a stag, that in time they lira 

 it down. Whatever may be the degree of credit du 

 tp these relations, we have well-authenticated accounts 

 of Indians, .in South America, who have carried dis- 

 patches from Buenos Ayres, on the river Plata, to 

 Lima, across immense forests, and over the rugged and 

 almost impassable mountains of the Andes, with a ce- 

 lerity equal to that which is attributed to the runners 

 of Ispahan, and absolutely incredible, were not these 

 performances repeatedly exemplified, and the vera- 

 city of these accounts sanctioned by the highest au- 

 thority. Man, in a civilized state, is ignorant of his 

 strength, and of the degree to which it might be aug- 

 mented by habitual and vigorous exercise. The con- 

 stitution of man is stronger than that of most animals, 

 and few of them equal him in longevity. He is an in- 

 habitant of every climate, and can by early habit ac- 

 custom himself to live on almost every kind of food. 

 The "human frame is so constituted, as to lasff ninety 

 or an hundred years, and if not shortened by acci- 

 dental causes, this appears to be the ordinary duration 

 of the life of man. Moderation of the passions, so- 

 briety, temperance, and exercise, at the surest pre- 



