June 22, 1900.] 



SCIENCE. 



975 



Reverend Father Searle and the Reverend 

 Father Woodman gave most valuable as- 

 sistance. Mr. Hoxie, of Port Royal, South 

 Carolina, and Mr. Little, of Wadesboro, 

 rendered valued assistance to Mr. Putnam 

 during totality. 



Professor Hale, of the Yerkes Observa- 

 tory, was a member of the party, while still 

 in general charge of the Yerkes expedition, 

 and his counsel and aid were of the great- 

 est service. Mr. Clayton, of Blue Hill 

 Meteorological Station, occupied a part of 

 the grounds of the Smithsonian party. 



The main object of the investigation was 

 of course the corona, and of this (first) a 

 photographic and visual study of its struc- 

 ture, 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 iilamentary structure close to the sun's 

 limb, and had never found in any photo- 

 graphs, 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 de- 

 vote to visual observations at the height of 

 14,000 feet. His wish to examine this inner 

 coronal region with a more powerful photo- 

 graphic telescope than any heretofore used 

 upon it, was gratified by the most valued 

 loan, by Professor 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-in. diameter, was 

 mounted so as to give a horizontal beam 

 from a coelostat clock-driven mirror by 

 Brashear, of 18-inch aperture, and used 

 with 30-inch square plates. To supplement 

 this great instrument, a 5-inch lens of 38- 

 ft. focus, loaned by Professor Young, was 

 pointed directly at the sun. This formed 



images upon 11x14 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, with 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 with- 

 out injury even to its suspending fiber, 

 a thread of quartz crystal y-gT^Tr ^^^^ ^^ 

 diameter. 



Besides these two chief aims (the photog- 

 raphy and bolometry of the inner corona),, 

 several other pieces of work were under- 

 taken, including the automatic reproduc- 

 tion of the ' flash spectrum ' by means of an 

 objective prism with the 135-ft. lens ; the 

 photographic study of the outer coronal 

 region, including provision for recognizing: 

 possible intra-mercurial planets, already 

 alluded to, visual and photographic obser- 

 vations 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 U. S. 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-ft. telescope ; F. E. 

 Fowle, Jr., assigned to 38-ft. telescope;; 

 Father Searle, directing the assembled tel- 

 escopes for the outer coronal region, and for 

 intra-mercurial planets, assisted by P. A.. 



