VI ADVERTISEMENT'. 



circumftances, are taken into confidera "">n, I have 

 the prefumption to hope that the generofity of the 

 Public will, one day, rank me with the few in num- 

 ber, who have devoted thcmfelves to the interefls of 

 humanity, at the expencc of their own fortune. 



I fliall not begin, at thefe years, to deviate from 

 the principles which have governed my life. I am 

 going to infert here, therefore, fome reflexions, 

 which would, perhaps, have come in more pro- 

 perly, in the advertifement prefixed to this third 

 Edition ; but I transfer them to this place, that 

 thofe who are difpofed to purchafe the fifth volume 

 feparately, may be informed of every thing which 

 1 have thought it neceflary to add, without being 

 obliged to buy the other four. I would have, in 

 like manner, annexed the additions which I made 

 to my firft Edition, on the fubjed of the elongation 

 of the Poles, and of the Currents of the Atlantic 

 Ocean, had not thefe additions been too confi- 

 derable in bulk. But if I do not introduce them 

 here, word for word, I repeat at leaft the fenfe of 

 them ; and to thefe I fubjoin new proofs, vvhich 

 demonflrate the certainty of thofe important truths. 



I have firft correfted, in the titles of this third 

 Edition, an error which had llipt into thofe of the 

 other two. It is indeed a matter of the laft indif- 

 ference to iTiy Readers, being no more than a tranf- 



pofition 



