CAMPBELL— CROCKER ECLIPSE EXPEDITION. 243 



corona prevail only during a short period of time at a well-defined 

 phase of maximum spottedness, or is the relation of outline form 

 to spot phase not very definite? Future eclipses should try to de- 

 termine the relationship more precisely than we can be said to know 

 it at present. The equipment needed for this work is inexpensive. 

 Cameras of moderate length, say from four to seven feet, are abun- 

 dantly powerful. 



There has been no satisfactory hypothesis proposed to account 

 for the undoubted relationship of coronal form and sunspot phase. 



Relationship of Coronal Streamers to Other Solar 

 Phenomena. 



The relations of coronal structure to other phenomena of the 

 sun, such as the prominences, sunspots, and faculae, are subjects of 

 inquiry with every corona recorded. Our slide No. 7, the eclipse 

 of 1898 in India, shows clearly, and I think for the first time, the 

 hooded forms of coronal structures which encircle some of the 

 prominences. The following eclipse, that of 1900 in Georgia, did 

 not show this feature, unless perhaps very mildly in the case of one 

 prominence. The larger prominences in 1900 were certainly unat- 

 tended by these hooded coronal forms. Later eclipses showed the 

 occasional presence of this phenomenon, but not strongly, until we 

 come to the eclipse of last year, when it was very marked indeed. 

 Slide No 8 is an exposure of one second on Seed thirty plates ob- 

 tained with the camera of forty feet focus. Nearly all of the larger 

 prominences and some of the smaller ones are enclosed by strong 

 and well-defined hoods. There can be no doubt, I think, that the 

 prominences and the curved streamers encircling them possess some 

 kind of intimate relationship. The greater part of the inner corona 

 recorded by this photograph consists of these curving streamers. 



Slide No. 9 is a four-second exposure made with the same in- 

 strument. The most of the strong coronal structure here shown 

 appears likewise to be under the control of, or to have intimate rela- 

 tionship of some kind with, the prominences which seem to lie at 

 centers of controlling influence. Nearly all of the structure to the 

 right of the sun is divided into three main compartments, each with 

 a prominence at the central point of contact with the sun's limb. 



