Mar. 7, 1872] 



NATURE 



567 



THE STRUCTURE OF THE CORONA 



AMONG the parties organised to observe the Total 

 Echpseof 1869, Aug. 7, that sent from the Cincinnati 

 Observatory was probably favoured above all others in 

 the advantage of having a comparatively elevated station 

 and an exquisite atmosphere. The publication of the work 

 done by this party has been delayed by the fact that for a 

 year subsequent to the eclipse I was wholly absorbed in 

 the labour attending the maintenance of the " Weather 

 Bulletin of the Cincinnati Observatory," and my subse- 

 quent occupations in the present office have entirely pre- 

 vented me thus far from even attempting the reduction of 

 our observations : the original note-books are at present 

 packed away with the library of the Observatory, await- 

 ing the removal and rebuilding of that institution. 



My own attention was expressly given to the structure 

 of the corona and coronal streamers, for which purpose 1 

 used the full aperture of an exquisite six-inch objective 

 (one that had received a prize at the Paris Exposition 

 Universelle), and which was loaned to the Eclipse Expe- 

 dition by Mr. T. G. Taylor, of Philadelphia. 



A short notice of the principal features noted by myself 

 was sent at once to the editor of the Astronomische 



Nachriclitcn, but has not yet been published, and I there- 

 fore take the liberty of restating through your wide-spread 

 journal the simple phenomena that I then saw. 



Our station was at Sioux Falls City (formerly Fort 

 Dakotah), in the south-eastern corner of Dakotah Terri- 

 tory, latitude 44°, longitude 97°, elevation about 1,500 feet 

 above sea-level, in the midst of an extended plateau. Rain 

 and cloud had continued up to a few hours previous to the 

 critical moment, but the atmosphere during the eclipse 

 was of surpassing steadiness and clearness. 



The altitude of the sun at time of totality was about 40°, 

 the local time 3.30 p.m., the duration of totality 4 minutes. 

 No sooner had totality begun than, after sketching in most 

 of the prominences as points of reference, I viewed the 

 corona without darkening glasses, and with a magnifying 

 power of probably 1 20 diameters. The whole interval of 

 totality was, unfortunately, not at my disposal, owing 

 partly to the very rough and faulty stand supporting the 

 telescope (everything tiad to be transported 100 miles by 

 mules into a wilderness), and partly to an interruption by 

 one of the members of the party ; but there seemed to me 

 to be no doubt of the facts as recorded, nor was I conscious 



of the least undue emotion that might have interfered with 

 my reliability as a witness, although it was the first total 

 eclipse that I have had the pleasure of observing. 



As seen through my inverting telescope, the structure 

 of the large protuberance on the right hand lower limb 

 was well made out. The neighbourhood of the sun was 

 examined to a distance of its own diameter (a radius of 

 possibly one degree from the sun's centre), but no trace 

 of the coronal rays as they were seen by others of my 

 party. The evidence as to the existence, shape, and posi- 

 tions of these streamers, as given by my six assistants, 

 was conclusive as to their actual appearance, with the 

 usual variations as to details. 



That they were not detected by the six-inch glass was 

 probably due to their dififused light and the small field of 

 view. On the apparent upper and left hand limb of the 

 sun, the six-inch glass showed the long series of red pro- 

 minences depicted in the photographs published by the 

 Naval Observatory. Above the greater portion of the arc 

 of the sun's limb thus covered, and extending somewhat 

 farther to the right, appeared to rise up three and possibly 

 more conical masses of pearly light. 



These were distinctlycontrastedagainsttlie light diffused 

 as the background of the field of view, and there was every 

 evidence that they had an identical structure and cause. 

 The outline of each of the pearly mountains was that of a 

 rounded cone, as shown in the drawing — exactly resem- 

 bling the kilns used in some branches of pottery and other 

 manufactures. The apices of the cones were blunted or 

 truncated, and not well defined ; the outlines of the sides 

 of the cones were quite sharp down to within a few 

 minutes of the sun's limb, when all three appeared to 

 begin to lose their distinctive characteristics. 



The height of the apices above the limb varied between 

 one-half and two-thirds of the solar radius ; the diameters 

 of the bases of the cones were probably included between 

 seven and three minutes. Each apex was of a slightly 

 dusky shade compared with the body of the cone. 



The most interesting feature was an unmistakable stria- 

 tion upon the surface of each cone ; the striie apparently 

 twisting spirally around up to the apex opposite to the 

 movement of the hands of a watch, as represented in the 

 accompanying drawing. 



I noticed no colouration of these stria; other than their 

 darker hue. The details of this striking and new phe- 

 nomenon interested me so much that I naturally enough 

 lost the observation of the third contact. The pearly 

 cones were on that limb of the sun from which the moon 

 was moving, and the details were every moment becoming 

 more distinct, when the growing height of the bank of red 

 protuberances was followed by the too speedy apparition 

 of the glowing sun beneath. 



Chagrin at the loss or imperfect observation of the third 

 contact caused me to forget to note whether the three 

 cones continued in view for any number of seconds there- 

 after. From the time of first recognising the pearly cones, 

 until their disappearance, probably thirty seconds elapsed 

 (1 am writing without my note-book or other aid to 

 memory), and I did not note any change in the appear- 

 ance of the stria;. 



The middle one of these cones caught my eye more 

 especially, and the impression was that the other two, 

 especially that on the right, was some distance behind it, 

 or possibly obscured by a cloud of haze in the solar at- 

 mosphere. At the time it seemed to me that I saw in the 

 central cone a column of smoke and hot gas ascending 

 high above the area of red flames, then visible on the 

 surface of the sun, and that the other two cones corre- 

 sponded to other areas of red tlames behind. The dif- 

 ference in character and position between these cones and 

 the coronal streamers as observed by the others with the 

 naked eye, and with opera glasses, seemed to argue that 

 the latter were very probably individual subjective pheno- 

 mena, or that they originated in the earth's atmosphere 



