260 



SCIENCE. 



[N. S. Vol. XV. No. 372. 



inches focal length.* A preliminary ex- 

 amination of these negatives was made at 

 the station and 92 stars of magnitude 8.6 

 to 8.8 were found in three of the regions. 

 The plates taken diiring the latter part of 

 totality show no star images, owing to the 

 increased cloudiness. A negative with long 

 exposure was secured with each of two 

 spectrographs, one having the slit tangen- 

 tial, the other radial. The principal Fraun- 

 hofer lines are shown in the outer corona 

 in both, none, however, being observable in 

 the extreme inner corona. Ten negatives 

 were secured ^vith a camera of 21 inches 

 focal length, having a double-image prism 

 placed in front of the objective. The two 

 images given by such a prism and camera 

 furnish a means of detecting by differ- 

 ential methods any considerable polariza- 

 tion in the corona. The axis of the prism 

 was set at several different position angles 

 between the sun's equator and his poles. 

 In this way all parts of the corona were 

 tested. The negatives secured show a large 

 percentage of polarization in the outer 

 corona and a slight amount in the inner 

 corona. The two spectrographs and the 

 polarigraph were designed and prepared 

 for use by Director Campbell and Assistant 

 Astronomer W. H. Wright. The great 

 southern comet was a conspicuous object in 

 the evening sky for several days and was 

 visible without aid for more than a week. 

 Photographs of it with a portrait lens were 

 secured on May 6. The exposures were 

 necessarily short, but show 3° or 4° tail. 

 A faint streamer is also shoAvn to the south, 

 making an angle of about 35° mth the 

 principal tail. A number of large copies, 

 on glass, of the eclipse photographs, as Avell 

 as lantern slides, v^ere shoAvn at the meet- 

 ing. 



* Two of the four lenses used in Sumatra were 

 kindly loaned for the purpose by Professor E. C. 

 Pickering, Director of the Harvard College Observ- 

 atory. 



A Martian Cloud: Pekcival Lowell. 



This paper gave an account of two pro- 

 jections seen upon the terminator of Mars 

 by Mr. A. E. Douglass at the Lowell Ob- 

 servatory on December 7 and 8, 1900; the 

 observations which gave rise to the popular 

 impression last year of signals from Mars. 

 Calculation showed them to belong to dif- 

 ferent parts of the planet and to have 

 moved during the time they were under 

 observation. Furthermore, the motion in 

 each case was approximately the same— 

 nearly due west in each case. Neither of 

 them reappeared on any succeeding night. 

 They thus showed themselves to be not 

 illuminated mountain tops, but sunset 

 clouds floating in the planet's atmosphere. 



Preliminary Statement of Results of Inter- 

 national Magnetic Observations made 

 during the Total Solar Eclipse of May 

 17-18, 1901: L. A. Bauee. 

 To further test the results obtained by 

 the United States Coast and Geodetic Sur- 

 vey magnetic parties during the total solar 

 eclipse of May 28, 1900, regarding a slight 

 magnetic effect that may be attributable 

 directly to some change produced in the 

 electrification of the upper atmospheric 

 strata by the abstraction of the sun's rays, 

 due to the interposition of the moon be- 

 tween the SITU and the earth, an appeal was 

 made for international cooperation in mag- 

 netic and allied observations during 

 the recent total solar eclipse. The repe- 

 tition of the observations was doubly in- 

 teresting owing to the fact that the 

 present eclipse occurred in the opposite 

 magnetic hemisphere to that of last year, 

 and hence the opportunity was afforded for 

 ascertaining whether the magnetic effect 

 was reversed in its general character to 

 that of last year, as is, for example, the case 

 with the diurnal variation in passing from 

 one magnetic hemisphere to the other. The 

 conditions, however, for obtaining observa- 



