May 17, 1900] 



NA TURE 



55 



passing on to the Atlantic from the shore of Virginia, 

 near Norfolk. The track is thus crossed by many of 

 the numerous railway systems of the Southern States, 

 exceptional facilities being thereby offered to observers 

 with large instruments. Information supplied by the 

 U.S. Weather Bureau indicates that stations in Alabama 

 and Georgia are most likely to be favoured with an un- 

 clouded sky \ hence the expeditions from the chief 

 American observatories will go there. Congress has 

 voted 5000 dollars to the Naval Observatory, and 4000 

 "dollars to the Smithsonian Institution, for the necessary 

 ■equipment. The Naval Observatory staff will organise 

 two expeditions, one going to North Carolina, the other 

 to Georgia, -so that the stations will be some 200 miles 

 apart, and wiU furnish valuable evidence as to the changes 

 to which the solar surroundings are subject. 



Ihe Smithsonian Institution will be represented by 

 Prof S. P. Langley, and the Princeton Observatory by 

 Prof. Youngs who will make a redetermination of the 

 vave-length of the green corona line. Prof Stone will 

 ■conduct a party from the University of Pennsylvania, 

 and although details are as yet unknown here, it is ex- 

 pected that expeditions from the Yerkes (Profs. Hale, 

 r>nrnard and Frost) and Lick (Prof Campbell) Observ- 

 ories will endeavour to obtain complete spectroscopic 

 e( ords of the various stages of the eclipse. The latter 

 \\'\\\ again use the 4o-(oot coronograph, giving a 4-inch 

 disc on plates 14x17 inches. Prof. Pickering, of the 

 Harvard College Observatory, proposes to make a 

 systematic search for an intra- Mercurial planet, and will 

 probably occupy a station in Alabama. 



By the kindness of Prof Young, the Rev. J. M. Bacon 

 has been enabled to organise an expedition to the States, 

 and his observations will be made in the neighbourhood 

 of Wadesborou^h, near the boundary between North and 

 South Carolina. The party will consist of the Rev. J. M. 

 Bacon, Miss Bacon, and Mr. and Mrs. Maskelyne. The 

 two latter observers will expose a telescopic kinemato- 

 graph on the corona during totality, and also an ordinary 

 kinematograph on the landscape during and after totality, 

 in the hope of recording the sweep of the moon's 

 shadow. The Rev. J. M. Bacon, using a telescopic 

 iiiiera, will photograph the corona at definite times 

 th respect to mid-totality, for determining the posi- 

 iiuns of sun and moon, and will expose a long film, 

 continuously driven, to the zenith before, during and 

 after totality, for recording the relative brightness of the 

 «ky during and without eclipse. By means of a kite, 

 he will also c-ompare the temperature of the air at an 

 altitude of several hundred feet and at ground-level. 

 Miss Bacon will attempt to photograph the outer corona 

 and extensions, and also a series of landscape photo- 

 :graphs showing the gradual diminution of illumination. 

 Special attention will also be devoted to the "shadow 

 bands," and to making standard photographic compari- 

 sons of the light of the corona with that of the full 

 moon. 



Prof. Burckhalter, of the Charbo Observatory, will 

 ]jhotograph the corona by means of a camera provided 

 with revolving screens, so adjusted as to give varying 

 exposures for the different regions. 



As the eclipse will occur at the American stations at 

 times from ih. 30m. to ih. 50m., we in England will be 

 able to hear of the results obtained there before the 

 observers in Spain have commenced operations. 



After leaving the American coast, the moon's shadow 

 crosses the Atlantic in a westerly direction, and reaches 

 the coast of Portugal, near Ovar, about 4.0 p.m. Thence 

 it rapidly passes across the peninsula, leaving the main- 

 land some little distance south of Alicante, and crossing 

 the Mediterranean to Algiers. Most of the European 

 expeditions will have stations along this line, chiefly at 

 Ovar, Santa Pola and Algiers. Taking the stations in 

 the order suggested by the progress of the eclipse, the 



NO. 1594, VOL. 62] 



distribution of the various parties and their plan of 

 operations will be as follows : — 



Ovar. — At this place, some twenty miles south of 

 Oporto, and five miles from the coast, will be stationed 

 one of the three official expeditions sent out by the 

 British Government, the observers being the Astronomer 

 Royal and Mr. Dyson, his chief assistant. The former 

 has arranged to take large scale photographs of the 

 corona with the 9-inch object-glass of the Thomson 

 photoheliograph at Greenwich, the primary image being 

 enlarged by a concave secondary magnifier to a scale of 

 about 4 inches to the sun's diameter, on plates 15x15 

 inches ; and also photographs with the double camera 

 used in previous eclipses, having a 4-inch rapid rectilinear 

 lens of 33 inches focus, and another of 13 inches focus, for 

 recording the extensions of the coronal streamers. 



Mr. Dyson's programme is purely spectroscopic. He 

 will have two slit spectroscopes belonging to Captain 

 Hills, and will endeavour to obtain photographs of the 

 spectrum of the "flash" and of the corona. 



Prof Miiller, of Potsdam, will from this station de- 

 termine the albedo of Mercury from direct photometric 

 comparisons with Venus, which will then be near its 

 greatest brilliancy. 



Santa Pola. — The second British official expedition 

 will be stationed here, some distance south of the town 

 of Alicante, on the east coast of Spain. The party 

 will be under the direction of Sir Norman Lockyer, 

 who will be primarily assisted by Mr. A. Fowler, Dr. 

 W. J. S. Lockyer and Mr. H. Payn. On their arrival at 

 Gibraltar, they will be taken on board H.M.S. Theseus., 

 of the Mediterranean squadron, which will then convey 

 them to their destination. As at Viziadrug in 1898, and 

 Norway in 1896, volunteers will be selected from the 

 ship's company, and parties detailed out for every 

 character of observation it is possible to make during a 

 total solar eclipse ; and in the interval between their land- 

 ing and the final day, besides the erecting and adjusting 

 of the instruments, the principal observers will have 

 their time fully occupied in giving lectures, practical 

 demonstrations, and rehearsals to the host of volunteers 

 who will undoubtedly offer themselves. 



Sir Norman Lockyer will make visual observations 

 with a 4-inch Cooke photo-visual telescope equatorially 

 mounted, and will give the signals for the whole of the 

 remaining human and mechanical machinery to be set 

 in motion. The following are the chief sections of the 

 observers : — 



20-foot Prismatic Camera. — This will be manipulated 

 by Mr. Fowler, and consists of a Cooke photo-visual 

 triplet lens, of 6 inches aperture and 20 feet 3 inches 

 focal length. Outside this will be placed the objective 

 prism, of 9 inches aperture and 45^ angle, which was 

 used at Viziadrug in 1898. The instrument will be fixed 

 horizontally, and fed with light from a 12-inch siderostat. 

 It is proposed to obtain instantaneous photographs of 

 the chromospheric spectrum at both internal contacts, 

 and long-exposure photographs of corona spectrum during 

 totality. It is hoped that the greatly increased disper- 

 sion given by this instrument will increase the contrast 

 between the line and continuous spectra of the corona, 

 and so render more accurate measurements of wave- 

 length possible. The plates used will be 15x2! inches. 

 b-inc/i Prismatic Camera. — This is the same instru- 

 ment which was used with success by Mr. Fowler in 

 1898, and will be under the charge of Dr. Lockyer. It 

 consists of a 6-inch object-glass by Henry, of 7 ft. 6 in. 

 focus, outside which are adjusted two objective prisms, 

 each of 6 inches aperture and 45"^ angle. The programme 

 with this instrument is similar to that of the 20-foot. 



Coronograp/is.—^t\&xa.\ coronographs of varying power 

 are being taken, the largest being under the charge of 

 Mr. Howard Payn, a gentleman who has generously 

 volunteered his services for the expedition. This instru- 



