THE TOTAL SOLAR ECLIPSE. 105 



and chromosphere are all projected into one point. Whether every 

 man who has gone forth to solve the riddle of the corona has fully 

 realized the odds against success is douhtful. 



Much has been written concerning a possible eruptive origin, or 

 about magnetic influences in shaping the forms of its streamers. It 

 has been shown that the details of the corona at one eclipse are totally 

 different from those at another, and that the outline form of the corona 

 is a function of the sun spot cycle. At sun spot maximum the general 

 form is nearly circular, and the polar streamers are nearly as bright as 

 the equatorial streamers. At minimum, the polar streamers are much 

 fainter than the equatorial ones, and long wings seem to extend out 

 approximately from the spot zones. It is a surprising fact that, with 

 all the changes of form, we do not yet know whether the materials 

 composing the streamers are moving in, or out, or both, or neither. 

 The epoch-making, large-scale coronal photographs by Schaeberle in 

 1893 opened a promising way of determining such facts, but astron- 

 omers have been slow in taking advantage of the opportunity. Pho- 

 tographs of the corona should be secured for this purpose at widely 

 separated stations — preferably at three or more stations — with essen- 

 tially identical instruments, and with equivalent exposures, in order 

 that results may be as nearly comparable as possible. This effort to 

 determine motion in the corona, it seems to me, is the most important 

 problem of the coming eclipse; and, fortunately, the circumstances of 

 widely separated stations in Labrador, Spain, Tunis and Egypt, and 

 promising weather conditions at the last three are favorable for the 

 attack. Considering all elements of the question, including that of 

 probable unsteadiness of the atmosphere at one or more stations, the 

 five-inch aperture, forty-foot focus cameras, promise the most directly 

 comparable, and therefore the best, results. The only case of motion 

 on coronal plates thus far observed seems to be that detected by Schae- 

 berle, on the Chile-Brazil- Africa plates of 1893; and in this instance 

 the moving mass was decided to be a comet, and not a part of the real 

 solar appendage. 



One of the most intensely interesting features ever observed in the 

 corona was the tremendous funnel-shaped disturbance recorded on the 

 Sumatra plates of 1901. Perrine was able to show, with essentially no 

 room for doubt, that the vertex of the disturbance was immediately 

 over the large and only sun spot visible on the sun in the week pre- 

 ceding and the week following the eclipse. The circumstances were 

 unusually favorable for reaching this conclusion: there was but one 

 sun spot; it was very near the limb at the time of the eclipse; there 

 was but one region of unusual disturbance visible in the corona; this 

 was on an extraordinarily large scale, and its vertex was near the sun's 

 limb; and the disturbance and the sun spot had identically the same 



