Page:Philosophical Transactions - Volume 095.djvu/152

138 It appears in general by my journal, and from these results, that when the degree of brightness at its maximum is less than usual, and its minimum not much decreased, the changes take place but very slowly, and cannot be settled with much accuracy, unless the observations have been made frequently, and with great attention; therefore, in summing them up, I think four of the first set and three of the second may be omitted, and then the duration at its maximum will be on a mean 8 + days, and ditto 20 — days

when it does not attain its usual brightness; and at its minimum - - - on a mean 9— days, and ditto 20 — days when its decrease is not so great as usual; the former observations make them 14 and 9 days.

Some of its degrees of brightness annexed to the results, have occasionally been noticed, as far as it was necessary, but the list of them I am going to give, is more exact and full. It will be there seen, that its brightness is seldom the same for two or three successive periods; that the change in half a rotation is sometimes from the 5th to the 7th magnitude, and sometimes only half a one or scarcely perceptible: its decrease has also been greater than by the former observations, particularly on September 15, 1798, and August 9, 1803, when it was less than the 9th magnitude, or had even disappeared.