Letter | Published:



THE spot seen on the sun by Mr. W. A. Holland (NATURE, vol. xxv. p. 316) would appear to have been simply a large sun-spot which made its appearance at the sun's east limb on November 15, and went off the disk on November 27. It is shown on photographs taken at Greenwich on November 16, 17, 18, 19, 20, 21, 23, 26, and 27. On November 21, 11h. a.m. it was north-east of the centre, Pos-angle 50° 27′, Dist. 0.188 of sun's radius, and on November 23 oh. it was north-west of the centre Pos-angle 313° 39′ dist. 0.412. The estimate of its size by Mr. Holland is very much exaggerated, the dimensions of the whole spot (nucleus and penumbra), as measured on the photographs, being one-twentieth of the sun's diameter in length, and one-twenty-fifth in breadth. The area, corrected for foreshortening and expressed in millionths of the sun's visible hemisphere, was 832 for the whole spot, and 152 for the nucleus on November 21, and 970 for the whole spot, and 171 for the nucleus on November 23. The spot had began to break up between November 21 and 23, and the area for November 21 is really the largest as applying to a single undivided spot. This spot is one of the largest yet recorded at Greenwich. Two other large spots of about the same size were photographed in 1881, on March 22 and June 1, their areas being respectively 919 for the whole spot, and 195 for the nucleus; and 931 for the whole spot, and 158 for the nucleus. The next largest spot in previous years was that of 1877 November, with an area of 801 for the whole spot, and 109 for the nucleus.

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