38 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



last of totality, and sensibly changed its form and 

 brilliancy, as n in violent commotion. It seemed to 

 the writer like a huge dense beacon-fire on a distant 

 hill-top, shorn of Its tongues of name, and seen 

 through an inverting telescope. There were^ sev- 

 eral variations of light and shade perceptible in ^ its 

 breadth. In depth it varied only in intensity, being 

 slightly faintest toward the horizon. 



A correspondent of the Chicago Times, writ- 

 ing from Des Moines, remarks that Professor 

 N. A. Rogers took a measurement, hy means 

 of the micrometer, of the largest colored pro- 

 tuberance, and estimates its greatest extension 

 at 38,000 miles. It seemed to grow up to that 

 height in a moment of time, like a flame, from 

 about hall* the size at first. At its base was a 

 mass tinged a crimson color, and like cumulous 

 clouds in composition. Along the southeastern 

 side of the sun, just before any portion of his 

 disk appeared after total eclipse, a long and 

 low line of crimson protuberances appeared, 

 which was dissipated by the full blaze of the 

 crescent sun a moment afterward. 



Dr. Peters made a spectrum analysis, and 

 found in all the five protuberances the red, blue, 

 and violet lines, which indicate hydrogen in a 

 state of high temperature. He discovered also 

 the double yellow lines that indicate sodium. 

 In addition to these, the spectrum showed 

 green lines and other shades of color, indica- 

 tive of still other metallic elements in the sun's 

 atmosphere, which are common to the earth. 

 Dr. Peters was of opinion that the observations 

 taken will throw much light upon the prob- 

 lems of the sun's constitution, and the sources 

 of his light and heat. So far as the hydrogen 

 lines of the spectroscope are concerned, his 

 observations verify those made by Rayet and 

 Herschel during the eclipse last year in India. 

 Professors Rogers and Hall directed their at- 

 tention just before and after the total eclipse to 

 the solution of the question of a lunar atmos- 

 phere. They acted upon the hypothesis that, 

 if there was such an atmosphere, the ends of 

 the sun's crescent just before and after totality 

 would have been partially obscured by coming 

 in contact with the moon's atmosphere. These 

 observers found no such phenomena, the cusps 

 being well defined and sharp throughout. 

 Hence they draw the deduction that the moon 

 is devoid of an atmosphere. 



The Naval Observatory party at Des Moines 

 succeeded in taking 123 photographs of the 

 eclipse, two being of the totality. They ap- 

 plied the spectrum analysis to five prominences, 

 no two of which were found to give the same 

 lines. No absorption lines were visible in the 

 spectrum of the corona ; it gave a continuous 

 spectrum with but one bright line. Professor 

 Harkness conducted this branch of the obser- 

 vations. The thermometer, as observed by 

 Professor Eastman, showed a fall of 13 dur- 

 ing the progress of the eclipse. 



Professor Newcomb searched, with two six- 

 inch object-glasses, for intra-Mercurial planets, 

 but none were visible. Venus and Mercury 

 appeared distinctly to the naked eye. 



Professor C. A. Young, of Dartmouth Col- 

 lege, who was with the Nautical Almanac 

 party at Burlington, Iowa, submitted two re- 

 ports of his observations to the American As- 

 sociation, in August, the substance of which he 

 afterward furnished to the American Journal 

 of Science. The following are the most im- 

 portant parts of the paper : 



The spectroscopic combination employed was com- 

 piled for the occasion from various instruments be- 

 longing to Dartmouth College, and diifered so much 

 in the relative proportion and arrangement of its 

 parts from those hitherto "used, that a brief descrip- 

 tion is perhaps necessary. f 



The telescope which formed the solar image was a 

 comet-seeker by Merz & Son, of 4 inches aperture 

 and 30 inches focal length. An ordinary Huyghenian 

 eye-piece enlarged the image so that, when it fell upon 

 the slit of the spectroscope at a distance of 5 inches, 

 it was 2i inches in diameter. The use of an eye- 

 piece gave an easy means for securing the accurate 

 focus of the limb at the slit, an adjustment of great 

 importance. The spectroscope proper had telescopes 

 of 2i inches aperture and 16* focal length (by Alvan 

 Clark). The eye-telescope was provided with an eye- 

 piece magnifying 18 times, and a wire micrometer, 

 constructed from a reading microscope, for determin- 

 ing the position of any new lines in the spectrum by 

 referring them to those already known. This, al- 

 though a very accurate method, was too slow to be 

 well adapted to eclipse observations, but was the 

 only arrangement I could construct with the time 

 and means at my command. 



The collimator had a slit i of an inch long and of 

 adjustable width. It was provided with a small 

 prism, which could be turned up so as to throw into 

 half the slit light from an electric spark formed be- 

 tween platinum electrodes by a small induction coil 

 and Leyden jar. 



It also carried a thin brass disk about 2 inches in 

 diameter, placed in front of the slit, with a hole of i 

 of an inch in the centre. This disk was covered with 

 white paper and graduated into sectors of 10 by lines 

 radiating from the centre. This graduated screen, 

 upon which the image of the sun was clearly visible 

 even during the totality, answered the purpose of a 

 finder, and its graduation furnished the means of de- 

 termining within less than 3 the position of any ob- 

 ject observed on the sun's limb, or of bringing any 

 desired portion of the limb to the slit. 



The spectrum was formed by a train of 5 prisms of 

 45 each, with faces 2* by 3i inches. They gave a 

 dispersion of about 18 between A and H, with a 

 total deviation of about 165 for the D line. The box 

 which contained them was so connected by a link 

 with the arm which carried the ey^e-telescope, that 

 whenever the latter was moved by its tangent-screw 

 along the spectrum the prism-box would turn through 

 an angle just half as great. Thus the prisms were 

 kept in the position of best definition for whatever 

 lines were in the middle of the field of view, the ex- 

 tent of which was sufficient to embrace D and E to- 

 gether. 



The telescope and spectroscope proper were firmly 

 secured to a wooden framework, and this was mount- 

 ed equatorially, with slow-motion screws in both 

 right ascension and decimation. 



The spectrum was about II inches broad (referred 

 to a distance of 10 inches) and about 45 long. It 

 showed all the lines on KirchofFs maps of the spec- 

 trum ; such lines as the nickel line between D x and 

 D 2 being perfectly distinct. 



Having arranged my instrument with the computed 

 point of contact across the centre of the slit, I had 

 the unspeakable gratification of seeing every thing 

 take place as expected. First, a full hair-minute be- 

 fore the time of contact, the sharp point of the needle 

 was truncated by the dark edge of the moon, then it 



