I GO 



APPENDIX. 



two {hips, and confequently to determine a bafe. The 

 angles being taken with an Hadley's quadrant from each 

 of the ihips, to the objefts whofe fituations are defigned 

 to be afcertained, the diftance may be found ; and, con- 

 fequently, their relative fituations. If there is a mega- 

 meter in each fhip, the altitudes taken from both fhips 

 at one inftant, and the angles of the different parts 

 of the coaft intended to be furveyed obferved with an 

 Hadley's quadrant at the fame time, will give the fitua- 

 tion with more accuracy and expedition than any method 

 of furveying from fliips hitherto pradifed ; with tlie 

 farther advantage of the certain means of detecting any 

 error in the obfervation, fo as to judge whether it is of 

 fufEcient importance to be attended to. The only pre- 

 cautions neceflary are j to make the obfervations at the 

 fame inftant, to prevent their being, affeded by any altera- 

 tion in the relative pofition of the fhips, as a very fmalL 

 one there would occafion a confiderable error in the 

 diftance ; and to be careful in chufing objeds fufficiently 

 defined and remarkable. This method of furveying has the 

 further advantage of giving the fcale of a coad: ; Seamen, 

 though they judge very accurately of their diftance from 

 places upon coafts well known to them, are very often 

 miftaken vv'hen they fall in with land they have never feen 

 before j of v*'hich we had, at firfl, fome inftances in this 

 voyage, the height of the mountains, before we knew the 

 fcale of the coaft, making us always think ourfelves nearer 

 the land than we reallv were. Where the coaft is at all 

 a high, 



