Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 2.djvu/43

]

"The line of no deviation was not found to correspond accurately with the north and south points of the compass on either of the occasions at Hobarton; but in 1840 coincided more nearly with the north by west and south by east, and in 1841 with the north by east and south by west. We may perhaps ascribe with probability irregularities of this nature to slight modifications in the distribution of the iron at different periods, which we cannot but view as of not unlikely occurrence; for example, such as might be occasioned by the ship being secured at different times by the starboard or larboard chain cable. In. looking through the observations of the Erebus, it is evident that there was no systematic or constant deviation of the plane of the ship's attraction from that of her principal section; but that the points of no disturbance were sometimes a little on the one side, and sometimes a little on the other, of the north and south points. It appears, therefore, not improper to class these irregularities with those others of accidental occurrence which occasion similar discordances in partial results, and are usually ranged under the general technical head of errors of observation.

"If, further, we compare generally the deviations in 1840 with those of June 1841, the latter appear systematically rather the more considerable in amount. Viewed as a single fact, this circumstance might be regarded simply as indicating that some change had taken place in the interim in the