"astronomy for 1889, 1890. 157 



under Mr. Keeler was at Bartlett Springs; one from Washington Uni- 

 versity observatory, St. Louis, under Prof. H. S. Pritchett at Norman; 

 one from Carleton College observatory under Professor Payne atObico; 

 and many other available ])oints were occupied by individual astron- 

 omers or photograpliers. At Cloven .'ale the Pacific Coast Amateur 

 Photographic Association was represented by 30 cameras. 



Professor Holden has published a full report of the Lick observatory 

 party and its coiiperators — the frontispiece being an admirable photo- 

 graph of the corona by Barnard, taken with a telescope of 3.j inches 

 aperture stopped down to Ijf inches. Professor's Holden's "conclusions " 

 in which he summarizes the observations are as follows: 



I. That the characteristic coronal forms seem to vary periodically as 

 the sun spots (and auroras) vary in frequency, and that the coronas of 

 1867, 1878, and 1889 are of the sann^, strongly marked type, which cor- 

 responds, therefore, to an ei)och of minimum solar activity. 



IL That so-called "polar" rays exist at all latitudes on the sun's 

 surface, and are better seen at the poles of the sun, simidy because 

 they are there projected again.st the dark background of the sky and 

 not against the equatorial extensions of the outer corona. There ap- 

 pears to be also a second kind of rays or beams that are connected with 

 the ring-like extensions. These are i)arts of the " groups of synclinal 

 structure" of Mr. Eauj'ard. 



III. The outer corona of 1889 terminated in branching forms. These 

 branching forms of the outer corona suf/gest the presence of streams of 

 meteorites near the sun, whicb, by their reflected light and by their 

 native brilliancy, due to the collisions of their individual members, 

 may account for the i)henomena of the outer corona. 



IV. The disposition of the extensions of the outer corona along and 

 very near the plane of the ecli])tic might seem to show that, if the 

 streams of meteorites above referred to really exist, they have long 

 been integral parts of the solar system. 



V. The photographs of the corona which were taken just before con- 

 tact II and just after contact III prove the corona to be a solar api)end- 

 age, and are fatal to the theory that any large part of the coronal 

 forms are produced by diffraction. - - - 



VI. The spectroscopic observations of Mr. Keeler show conclusively 

 that the length of a coronal line is not always an indication of the 

 depth of the gaseous coronal atmosphere of the sun at that point, and 

 hence to indicate the important conclusion that the true atmosphere of 

 the sun niay be comi)aratively shallow. 



VII. Mr. Keeler draws the further conclusion in his report - - - 

 that the " i)olar" rays are due to beams of light from brighter areas of 

 the sun illuminating the suspended particles of the sun's gaseous envel- 



NoTE. — The couclu.sions III and IV appear to be contradictory to that expressed in 

 I. The electrical theory auiioniiced hy I>r. Ilyirins iu the Kakerian lecture for 18H'> 

 eeeriis to reconcile the coucluaions I, III, and IV, 



