Partly in deference to the report of the United States Weather Bureau, from which it appeared that the chance of a fair eastern sky on the morning of the eclipse was about 8 to 1, and after examination by Mr. Abbot of many stations in North Carolina, Wadesboro, of that State, was selected early in April as the site of the Smithsonian observations. The advantages of Wadesboro being also recognized by Professor Young, of Princeton, Professor Hale, of Yerkes Observatory, and the Rev. J. M. Bacon, of the British Astronomical Association, it came about that four large observing parties, besides several smaller ones and numerous excursionists from the surrounding country, were all joined to produce at Wadesboro one of the largest company of eclipse observers ever assembled for scientific purposes. It is a matter for congratulation that the sky at Wadesboro upon the day of the eclipse was cloudless and clearer than the average, so that the efforts of the observing forces were not thwarted by any circumstances beyond their control. The provisions of the Mayor and authorities of Wadesboro for preventing intrusion before and during the eclipse, and thus securing an undisturbed field of operations, deserve especial recognition. Further than this, the many acts of courtesy and hospitality to the visiting astronomers on the part of the townspeople will long be remembered by the recipients.
The Smithsonian party proper consisted of thirteen observers, and included Mr. Langley, Mr. Abbot, aid acting in charge of the Smithsonian astrophysical observatory; Mr. Smillie, in charge of photography; Mr. Putnam, of the United States Coast Survey; Mr. Fowle, Mr. Mendenhall, Mr. Child, Mr. Draper, Mr. Gill, Mr. Kramer and Mr. Smith. Included with these, the Rev. Father Searle and the Rev. Father Woodman gave most valuable assistance. Mr. Hoxie, of Port Royal, S. C., and Mr. Little, of Wadesboro, rendered valued assistance to Mr. Putnam during totality.
Professor Hale, of the Yerkes Observatory, was a member of the party, while still in general charge of the Yerkes expedition, and his counsel and aid were of the greatest service. Mr. Clayton, of Blue Hill Meteorological Station, occupied a part of the grounds of the Smithsonian party.
The main object of investigation was, of course, the corona, and of this, (first) a photographic and visual study of its structure; with, (second) a determination by the bolometer whether appreciable heat reaches us from it, and, if possible, an examination of the form of its spectrum energy curve.
The writer had been particularly struck, when observing the eclipse of 1878 on Pike’s Peak, by the remarkable definiteness of filamentary structure close to the sun’s limb, and had never found in any photographs, not even in the excellent ones of Campbell taken at the Indian eclipse of 1898, anything approaching what he saw in the few seconds which he was able to devote to visual observations at the height of fourteen thousand feet. His wish to examine this inner coronal region with a more powerful photographic telescope than any heretofore used upon it, was gratified by the most valued loan by Prof. E. C. Pickering of the new 12-inch achromatic lens of 135 feet focus, just obtained for the Harvard College Observatory. This lens, furnishing a focal image of more than 15 inches diameter, was mounted so as to give a horizontal beam from a cœlostat clock-driven mirror by Brashear, of 18 inches aperture, and used with 30-inch square plates. To supplement this great instrument, a 5-inch lens of 38-feet focus, loaned by Professor Young, was pointed directly at the sun. This formed images upon 11 × 14 plates moved in the focus of the lens by a water clock. Specially equatorially mounted lenses of 6, 4 and 3-inch aperture, driven by clock work, were provided for the study of the outer corona, and the search for possible intra-mercurial planets.
For the bolometric work, the massive siderostat with its 17-inch mirror, and a large part of the delicate adjuncts employed at the Smithsonian Institution in recent years, to investigate the sun’s spectrum, was transported to Wadesboro. The excessively sensitive galvanometer reached camp without injury even to its suspending fibre, a thread of quartz crystal 1-15,000 inch in diameter.
Besides these two chief aims (the photography and bolometry of the inner corona), several other pieces of work were undertaken, including the automatic reproduction of the ‘flash spectrum’ by means of an objective prism with the 135-foot lens, the photographic study of the outer coronal region, including provision for recognizing possible intra-mercurial planets, already alluded to, visual and photographic observations of times of contact, and sketches of the corona, both from telescopic and naked-eye observations.
The assignment of the observers was as follows: Mr. Langley, in general charge of the expedition, observed with the same 5-inch telescope used by him on Pike’s Peak in 1878, which was most kindly lent for this special comparison by Professor Brown, of the United States Naval Observatory; C. G. Abbot, aid acting in immediate charge, assigned with C. E. Mendenhall to the bolometer; T. W. Smillie, having general direction of the photographic work, made exposures at the 135-foot telescope; F. E. Fowle, Jr., assigned to the 38-foot telescope; Father Searle, directing the assembled telescopes for the outer coronal region, and for intra-mercurial planets, assisted by P. A. Draper and C. W. B. Smith, exposed two cameras of 3-inch aperture and 11 feet focus, and two of 4½-inch aperture and 3½ feet focus, all four of these telescopes being mounted on a single polar axis driven by an excellent clock; De Lancey Gill, assisting Mr. Smillie, removed the flash spectrum objective prism at second contact, and made a single long exposure with a 6-inch photographic lens of 7½ feet focus equatorially mounted; Assistant G. R. Putnam, who, by the kindness of the superintendent of the United States Coast Survey, was detailed for latitude,[C] longitude[D] and time observations, also observed contacts, directed the striking of signals by Mr. Little, and rendered other valuable services. Mr. Putnam was assisted in recording contacts by Mr. Hoxie. R. C. Child, observing with a 6-inch telescope of 7½ feet focus, made sketches with special reference to inner coronal detail, and was in addition charged with all electrical circuits for chronograph and automatic photographic apparatus. Father Woodman, with 3½-inch telescope, observed contacts and made sketches.
[C] 34°, 57′, 52″ N.
[D] 5h., 20m., 17.8s. W.