Image: A voyage towards the North Pole - undertaken by His Majesty's command, 1773 (1774) (14781135374)

Description: Identifier: voyagetowardsnor00mulg (find matches) Title: A voyage towards the North Pole : undertaken by His Majesty's command, 1773 Year: 1774 (1770s) Authors: Mulgrave, Constantine John Phipps, Baron, 1744-1792 Phipps, Constantine John, 1744-1792 Subjects: Racehorse (Ship) Publisher: London : Printed by W. Bowyer and J. Nichols for J. Nourse Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: leys Sextant of eighteeninches radius, made by Dollond; and fonietimes byCaptain Phipps, with a fmaller of four inches radius,made by Ramfden, which commonly agreed with theother within a minute. The error of the fextantwas generally found by obferving the diameter of theSun ; which if the fame as double the femidlameterfet down in the Nautical Almanac, fliewed that theinflrument was perfedlly adjufted ; if it differed, thedifference 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 ofthe Suns diameter feveral times, and from the meanof the refult found the error of the fextant. This errorwill equally affedt all the obfervations taken nearthe fame time, and therefore cannot be difcoveredfrom the comparifon of feveral obfervations. Underthe equator, an error of one minute in altitude, nearthe prime vertical, will only produce an error offour feconds in the apparent time; but in the latitude of Text Appearing After Image: APPENDIX. * of eighty degrees it will caufe an error of twenty-three feconds. As we generally took feveral fucceffive ob- fervations, any error in the obfervation itfelf will be generally independent of the reft; and as I have calcu- lated each feparately,- the conclufions will fhew which are erroneous, by their differing much from the mean of all, which cannot but be very near the truth. In calculating thefe obfervations, I found by the logboard how much we had altered our latitude (ince the lafl: obfervation; and fometimes, when we had** an obfervation the noon following the obfervation for the time, the latitude of the fhip at the time the altitudes were taken was inferred from it. As mod** of our altitudes were obferved when the fun was near* the prime vertical, a fmall error in the latitude will not produce any conGderable change in the time;* indeed, if it is exadlly in the prime vertical, it will not.* make any change at alh * To find the Longitude from thefe obfervations: toth Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
Title: A voyage towards the North Pole - undertaken by His Majesty's command, 1773 (1774) (14781135374)
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