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APPENDIX. 



Account of the Astronomical Observations and 

 Time-Keepers, by Mr. Lyons. 



'nr^HE obfervations for finding the time at fea, were 

 •^ taken with a brafs Hadley's Sextant of eighteen 

 inches radius, made by Dollond; and fonietimes by 

 Captain Phipps, with a fmaller of four inches radius, 

 made by Ramfden, which commonly agreed with the 

 other within a minute. The error of the fextant 

 was generally found by obferving the diameter of the 

 Sun ; which if the fame as double the femidlameter 

 fet down in the Nautical Almanac, fliewed that the 

 inflrument was perfedlly adjufted ; if it differed, the 

 difference was the error of the fextant. It was necef- 

 fary to know this error of adjuftmcnt very cxadly, 

 and therefore I generally repeated the obfervation of 

 the Sun's diameter feveral times, and from the mean 

 of the refult found the error of the fextant. This error 

 will equally affedt all the obfervations taken near 

 the fame time, and therefore cannot be difcovered 

 from the comparifon of feveral obfervations. Under 

 the equator, an error of one minute in altitude, near 

 the prime vertical, will only produce an error of 

 four feconds in the apparent time ; but in the latitude 



of 



