Ch.I. south AMERICA. 19 



tion in the courfe, than that of the needle by which the 

 iliipis ileered ; as was the cafe with me in falling from 

 Martinico toCurafao, and likewife of all the artiils on 

 board the ihip. Another error incident to navigators, 

 though not fo much their own, is to ñeerthe fhipbyone 

 needle, and obferve the variation by another; for 

 though they have been compared, and their differences 

 carefully obfervedj their motions beingunequal, though 

 at the beginning of the voyage iht* difference was only 

 a certain number of degrees, the continual friilion of 

 the former on the pivot, renders the point of the needle, 

 on which it is fufpcnded, more dull than the other, 

 which is only hung when they make obfervations, being 

 at all other times kept with thegreateft care; and hence 

 proceeds the change obfervable in their differences. 

 In order to remedy this evil, all needles intended to be 

 ufed at fea íhould be cqaally proper for obferving the 

 variation ; and the obfcrvation made with thofe before 

 placed in the bittacle ; and, to improve the charts of 

 variation, fliould be touched in the fame manner, and 

 adjufled to the meridian of a place, wliere the exat'H. 

 variation is known. Thus obfervations made in the 

 fame places by different Ihlps, would not be found fo 

 coniiderably to vary ; unlefs the interval of time be- 

 tween two obfervations be luch as to render fenlible 

 that difference in the variation, which has been obferved 

 for many years pafl, and is allowed of by all nations. 



These are the caufes of the manifeñ difference be- 

 tween needles ; there may be others', but this is not 

 tbe proper place for enumerating them. 



CHAP. II. 



Defcription of Carthagena, 



ON the 9th of July 1735, v-e landed, and Don 

 George Juan and myfelf immediately waited on 

 the governor of the place. We were informed that the 



C 2 FreBch 



