ch. 1. SOUTH America. 



tionin thecourfe, than that of the needle by which the fhip 

 is fteered ; as was the cafe with me in failing from Mar- 

 tinico to Curafao, and likewife of all the artifts on board 

 the fhip. Another error incident to navigators, though 

 not fo much their own, is, to fteer the fhip by one needle^ 

 and obferve the variation by another; for though 

 they have been compared, and their differences care- 

 fully obferved, their motions being unequal, though at 

 the beginning of the voyage the difference was only a 

 certain number of degrees, the continual fridlion of the 

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

 which it is fufpended, more dull than the other, which 

 is only hung when they make obfervations, being at all 

 other tifnes kept with the greatefh care ; and hence pro- 

 ceeds the change obfervable in their differences. In or- 

 der to remedy this evil, all needles intended to be ufed at 

 fea fhould be equally proper for obferving the variation % 

 and the obfervation made with thofe before placed in the 

 bittacle : And, to improve the charts of variation, fhould 

 be touched in the fame manner, and adjufted to the me- 

 ridian of a place, where the exa6l variation is known* . 

 Thus obfervations made in the fame places by different 

 fhips, would not be found fo confiderably to vary ; un- 

 lefs the interval of time between two obfervations be fuch 

 as to render fenfible that difference in the variation^ 

 which has been obferved for many years pad, and is al- 

 lowed of by all nations* 



These are the caufes of the manifeft difference be- 

 tween needles there may be others, but this is not the 

 proper place for enumerating them. 



C H A P. IL 



Defcrtption of Carthagena, 



ON the 9th of July 1735, we landed, and Don 

 George Juan and myfelf immediately waited on 



C 2 the 



