34 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



degrees from the sun. I had previously committed 

 to memory the relative places of stars near the sun 

 down to the seventh magnitude, and the chart ot the 

 region was placed conveniently in front of me for 

 ready reference whenever required. The first sweep 

 began with the sun in the middle of the field, and 

 extended eastward about eight degrees and back, 

 and I saw Delta Cancri and smaller stars marked 

 on the chart. The next sweep was one field farther 

 south, and eastward and back as before. Then 

 placing the sun in the field, I commenced a corre- 

 sponding sweep to the westward. Between the sun 

 and Theta Cancri, and south of the middle of the 

 field, I came across a star, estimated at the time to 

 be of the four and a half magnitude, which shone 

 with a ruddy light, and certainly had a larger disk 

 than the spurious disk of a star. The focus of the 

 eyepiece had been carefully adjusted beforehand 

 and securely clamped, and the definition was excel- 

 lent. I proceeded therefore to mark its position on 

 the paper circles, and to record the time of observa- 

 tion. It was designated by a. The place of the sun 

 had been recorded a few minutes previously and 

 marked s. Placing my eye again at the telescope, I 

 assured myself that it had not been disturbed, and 

 proceeded with the search. I noticed particularly 

 that the object in question did not present any elon- 

 gation, such as would be probable were it a comet in 

 that position. In the next and final sweep I brought 

 into the field what I supposed to be Zeta Cancri, 

 although it appeared very much brighter than what 

 I expected from the appearance of Delta Cancri, 

 which I had seen in the first sweep. I proceeded 

 to record its position on the circles with the desig- 

 nation b. 



The positions of these objects as finally de- 

 termined by Prof. Watson were as follows : 



Prof. Watson has no donbt whatever that the 

 first is a planet within Mercury's orbit. " In 

 regard to (&)," he remarks, " it is possible, but 

 not probable, that the pointing of the instru- 

 ment may have been disturbed by the wind. 

 I marked the position on the hour circle first, 

 and but a moment was occupied in passing from 

 the eyepiece to the hour circle. I believe that 

 this observation can be relied upon as giving 

 the place of a second intra-Mercurial planet." 



Mr. Lewis Swift of Rochester, N. Y., who 

 observed from a position in the vicinity of Den- 

 ver, Col., saw also the planet (a), near Theta 

 Cancri. He estimated its brightness as about 

 equal to that of a fifth -magnitude star. 



Observations of the Corona. Profs. Dra- 

 per, Barker, and Morton, together with Mr. 

 Edison, gave special attention to the corona, 

 in order, if possible, to determine its true na- 

 ture. With these observers, the main question 

 for decision was whether the corona is an in- 

 candescent, self-luminous gas, or whether, like 

 the planets, it shines by reflected light. Their 

 station was at Rawlins, in latitude 41 48' 50", 

 longitude 30 11' 0" west from Washington; 

 height above the sea, 6,732 feet. The photo- 

 graphic and photo-spectroscopic work was by 

 Dr. Draper; -the observations Avith the analyz- 

 ing slit spectroscope, by Prof. Barker; and 



those with the polariscope, by Prof. Morton. 

 The spectrum of the corona was not that of 

 an incandescent gas ; its photograph indicated 

 a height equal to two thirds of the sun's diam- 

 eter, or nearly 600,000 miles ; the polarization 

 was shown by Prof. Morton to be such as would 

 be produced by reflected light ; the Fraunhofer 

 dark lines were seen in the spectrum of the 

 corona ; and finally, Mr. Edison's tasimeter 

 was violently affected by the coronal heat. 

 " The general conclusion," says Dr. Draper, 

 "that follows from these results is, that on 

 this occasion we have ascertained the true na- 

 ture of the corona, viz. : it shines by light re- 

 flected from the sun by a cloud of meteors sur- 

 rounding that luminary ; and that on former 

 occasions it has been infiltrated with materials 

 thrown up from the chromosphere, notably 

 with the 1474 matter and hydrogen. As the 

 chromosphere is now quiescent, this infiltra- 

 tion has taken place to a scarcely perceptible 

 degree recently. This explanation of the na- 

 ture of the corona reconciles itself so well with 

 many facts that have been difficult to explain, 

 such as the low pressure at the surface of the 

 sun, that it gains thereby additional strength." 



The apparent extent of the corona as ob- 

 served at different stations was remarkably 

 various ; the difference being doubtless owing 

 in part to the relative altitudes of the points 

 of observation. The measures of Mr. Eas- 

 terday gave a height of 700,000 miles above 

 the sun's surface. Profs. Langley and New- 

 comb traced the coronal matter along the eclip- 

 tic to a distance of more than 9,000,000 miles 

 from the sun. Prof. Cleveland Abbe, who 

 observed with the naked eye from Pike's Peak, 

 traced one coronal stream along the ecliptic to 

 a distance of six diameters of the sun, and an- 

 other at right angles to the ecliptic to a dis- 

 tance of five diameters. The light of the for- 

 mer was "an exceedingly faint and delicate 

 white, apparently overlaid or intermingled 

 with the blue of the atmosphere. There was 

 no decided increase of brightness in that part 

 of the ray near the solar limb, nor in the axis 

 of the beam ; but the delicate light continued 

 uniform up to the corona in whose glare it 

 was lost." Prof. Abbe regards these coronal 

 streams as collections of meteors moving in 

 cometary orbits about the sun, and rendered 

 visible by reflecting the solar light the view 

 now also adopted by several other astronomers. 



Prof. C. A. Young, Mr. Lockyer, and other 

 observers regard the observations of 1878 'as 

 demonstrating an intimate relation between 

 the sun's condition as to the number of its 

 spots, and the constitution of the corona. The 

 recent eclipse was at a time of sun-spot mini- 

 mum. Indeed, there has been a marked pau- 

 city of spots for the last two years. The 

 chromosphere has been free from agitation ; 

 the flame-colored prominences have been few 

 and small ; and, in short, the whole solar sur- 

 face has been remarkably quiescent. Corre- 

 sponding to this condition of the sun, the 



