ON THE SOLAR CORONA. 761
it is obvious the rift might have gone round with the sun, but there is no positive evidence on this point.*]
As the comparison of the English plates with those taken at Caroline Island possesses great interest, I think it well to put on record here a let- ter written by Mr. Lawrence to Professor Stokes, dated Sept. 14, 1883 :
"Dr. Huggins called upon Mr. Woods this morning and showed us the drawings Mr. Wesley has made of his coronas. He told us that he particularly did not wish to see our negatives, but that he would like us to compare his results with ours. We did so, and found that some of the strongly marked details could be made out on his drawings, a rift near the north pole being especially noticeable ; this was in a photograph taken on April 3d, in which the detail of the northern hemisphere is best shown, while the detail of our southern hemisphere most resembles the photograph taken on June 6th ; in fact, our nega- tives seem to hold an intermediate position. Afterward I went with Dr. Huggins and Mr. Woods to Burlington House to see the negatives. The outline and distribution of light in the inner corona of April 3d are very similar to those on our plate which had the shortest exposure ; the outer corona is, however, I think, hidden by atmospheric glare. As a result of the comparison, I should say that Dr. Huggins's coronas are certainly genuine as far as 8' from the limb."
Though the plates which were obtained during the summer of 1883 appeared to be satisfactory to the extent of showing that there could be little doubt remaining but that the corona had been photographed without an eclipse, and therefore of justifying the hope that a success- ful method for the continuous investigation of the corona had been placed in the hands of astronomers, yet, as the photographs were taken under the specially unfavorable conditions of our climate, they failed to show the details of the structure of the corona.
The next step was obviously to have the method carried out at some place of high elevation, where the large part of the glare which is due to the lower and denser parts of our atmosphere would no longer be present. I ventured to suggest to the Council of the Royal Society that a grant from the fund placed annually by the Government at the disposal of the Royal Society should be put in the hands of a small committee for this purpose. This suggestion was well received, and a committee was appointed by the Council of the Royal Society. The committee selected the Riff el, near Zermatt in Switzei'land, a sta- tion which has an elevation of 8,500 feet, and the further advantages of easy access, and of hotel accommodation. The committee was fortunate in securing the services, as photographer, of Mr. Ray Woods, who as assistant to Professor Schuster had photographed the corona during the eclipse of 1882 in Egypt, and who in 1883, in conjunction with Mr. Lawrence, had photographed the eclipse of that year at Caroline Island.
- See Plates XI and XIa, "British Association Report," 1S83, p. 348.