H. Draper—The Solar Eclipse. 227 
Art. XXIV.—The Solar Eclipse of July 29th, 1878 ; by 
Professor HENRY DRAPER, M.D. 
As I have recently been giving attention to the subject of 
solar spectroscopy in consequence of my discovery of oxygen in 
e sun, it seemed to be desirable to take advantage of the total 
eclipse of July 29th, to gain as precise an idea as possible of the 
nature of the corona, because the study of that envelope has 
been regarded as impossible at other times. The main point to 
ascertain was whether the corona was an incandescent gas shin- 
ing by its own light, or whether it shone by reflected sunlight. 
For this purpose I organized an expedition, and was fortun- 
ate enough to secure the codperation of my friends Professors 
Barker and Morton and Mr. Edison. The scheme of operations 
was as follows: 1st, the photographic and photo-spectroscopic 
work as well as the eye slitless spectroscope were to in 
charge of my wife and myselt; 2d, the analyzing slit spectro- 
scope was in charge of Professor Barker, with the especial 
object of ascertaining the presence of bright lines or else of dark 
Fraunhofer lines in the corona; 3d, the polariscopic examina- 
tions were confided to Professor Morton, who was also to spend 
a few moments in looking for bright or dark lines with a hand 
spectroscope ; 4th, Mr. Edison carried with him one of his newly 
invented tasimeters with the batteries, resistance coils, Thom- 
son’s galvanometer, etc., required to determine whether the 
heat of the corona could be measure 
due to a special incandescent gas; 2d, a fine Peggy OE the 
corona was obtained, extending, in some parts, to a height of 
more than twenty minutes of arc, that is, more than 500,000 
miles; 8d, the Fraunhofer dark lines were observed by both 
Professors Barker and Morton in the corona; 4th, the polariza- 
tion was shown by Professor Morton to be such as would 
answer to reflected solar light; 5th, Mr. Edison found that the 
heat of the corona was sufficient to send the index beam of 
light entirely off the scale of the galvanometer. Some negative 
results were also reached, the principal one being that the 
1474K, or so-called corona line, was either very faint or else 
not present at all in the upper part of the corona, because it 
could not be observed with a slitless spectroscope and the slit 
Spectroscope only showed it close to the sun. 
e general conclusion that follows from these results, is, 
that on this occasion we have ascertained the true nature of the 
