Page:Philosophical Transactions - Volume 095.djvu/146

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132
Mr. Pigott's Investigation of the Changes

Its rotation on its axis was, in 1796, estimated at 623/4 days, from a mean of six observations of its greatest and least brightness. Here follow about 26 similar determinations, most of them the results of very accurate observations; and as they probably will in future be compared with others, I have examined them repeatedly with the utmost care, attending particularly to the progression of their changes.

Table I.

Dates when at its greatest
Brightness.
Magnitudes Dates when at its least
Brightness
Magnitudes
1796. September 17 5 1796. September 3 6
November 13 5 October 22 6
1797. May 14 : 5 + 1797. July 10 5.6
August 7 5 September 15 6
October 15 6.5 November 6 6
1798. July 29 5 + 1798. July 10 6
October 25 5.6 September 15 9.0
December 5 : : 5.6 November 10 6
1799. June 1 : : 6.5 1799. July 4 7
August 7 5 September 16 6
October 11 5 + November 5 : 6.7
1801. July 14 : 5 1801. June (middle) : 6
September 24 5 August 21 6.7
October 16 6.5

The + and — annexed to the magnitudes denote them to be more or less bright; the doubtful results are marked with dots; all the others are esteemed exact, except those of August 7, 1797, and August 21, 1801, which are in a small degree less so. From these determinations the rotation on its axis may be computed as follows.