October 20, 1911] 



SCIENCE 



5;n 



Preliminary Beport on the Photographs of Hal- 

 ley's Comet taken at Sonolulu, E. I., hy Fer- 

 dinand Ellerman in 1910: E. E. Babnaed. 

 (Read by Dr. Sloeum.) 



The expedition for the observation of Halley's 

 comet, sent in 1910 to the Hawaiian Islands by 

 the Astronomical and Astrophysical Society of 

 America in the sole charge of Mr. Ferdinand 

 Ellerman, established itself on the south slope of 

 Diamond Head about five miles southeast of Hon- 

 olulu, Oahu Island, and at an elevation of about 

 one hundred and fifty feet above sea-level. 



The instrumental equipment consisted of a 

 Warner and Swasey mounting with a six-inch 

 Clark lens, loaned by the Lick Observatory; a 

 metal camera with a Brashear six-inch portrait 

 lens of thirty-two inches focal length, loaned by 

 Brashear; and a wooden camera with a two-and- 

 one-fourth-inch Bausch and Lomb Optical Com- 

 pany-Zeiss Tessar lens of nine and seven eighths 

 inches focus, loaned by the Bausch and Lomb 

 Optical Company. The cameras were carried on 

 the telescope tube. 



IMr. Ellerman secured an excellent series of 

 photographs of the comet and made very impor- 

 tant though negative observations at the time of 

 the comet's transit across the sun on May 18. 

 On this date, though small spots could be distinctly 

 seen on the sun's surface, no trace of the comet 

 or its nucleus was evident. 



Visual observations of the extent of the tail of 

 the comet on the mornings of May 15, 16 and 17 

 accord with observations made elsewhere. In the 

 record of May 24 occurs the following note: 

 "Nucleus of comet appeared double or dumbbell- 

 shaped. Separation estimated about 20" of are." 

 Mr. Ellerman secured sixty photographs of the 

 comet with the six-inch Brashear camera and thir- 

 teen with the Tessar. Many of these photographs 

 are exceedingly interesting, but in the main they 

 agree with other photographs in showing that very 

 little of the abnormal occurred in the phenomena 

 of the comet's tail. One thing apparent in the 

 phenomena of Halley's comet which was first 

 shown in Daniel's comet was the fact that on sev- 

 eral occasions two slender streams, which doubtless 

 had their original intersections in the nucleus, 

 receded from the head still connected as if the 

 source of supply were going out vrith them. 



The length and breadth of the tail of Comet 

 Halley as shown on Mr. Ellerman 's Tessar plates 

 are here tabulated. 



Near its extremity the tail was always very faint 

 on these photographs. On the plate of May 14 



at least twelve degrees of the forty-nine recorded 

 was very faint. 



The Solar Prominence of October 10, 1910: Fred- 

 erick Slocum. 



This paper is based upon a series of photo- 

 graphs taken in the light of calcium with the 

 Rumford spectroheliograph of the Yerkes Observa- 

 tory, and upon some hydrogen photographs, nearly 

 simultaneous, taken by Mr. Ellerman at the Solar 

 Observatory, on Mount Wilson. 



The prominence extended from latitude — 24° 

 to latitude — 40° in the east limb, and reached a 

 height of 105,000 km. In connection with the 

 speetroheliograms are discussed the relations of 

 hydrogen and calcium images, absorption effects 

 due to dark masses projected against bright prom- 

 inences and gravitational effects upon prominence 

 particles. 



Direct photographs of the H and K region of 

 the spectrum between X 3,910 and A 3,980, were 

 made with the slit across different parts of the 

 prominence. These show the H, and K3 lines fol- 

 lowing sinuous courses throughout the whole 

 lengths of the H, and K. lines. The local relative 

 displacements of the emission and absorption lines 

 amount to ± 0.20 A, corresponding to velocities 

 of about 15 km. per second if the displacements 

 are manifestations of the Doppler effect. 

 Vapor-density Effects on the Calcium Lines H, K 

 and g: Oliver J. Lee. (Bead by Dr. Slocum.) 

 The experiment discussed in this paper was 

 undertaken because of the writer's interest in the 

 anomalies shown by these lines of calcium in 

 radial velocity work, and limits itself to deter- 

 mining the relative vapor-densities at which self- 

 reversal occurs. 



The high temperature, about 2,500° C, required 

 to vaporize and incandesce calcium makes the 

 usual apparatus for experiments on vapor-density 

 quite useless. The rate of volatilization of the 

 element under standard conditions was assumed to 



