ASTRONOMICAL PHENOMENA AND PROGRESS. 



33 



pass from their condition of extreme rarity and 

 intense cold to that of greater compression and 

 higher temperature, until reaching, or nearly 

 reaching, the sun's surface, they ignite, giving 

 rise to a great development of heat. The re- 

 sults of combustion aqueous vapor and car- 

 bonic acid will be borne by the centrifugal 

 force toward the solar equator, and thence 

 thrown outward into space. 



4. According, then, to Dr. Siemens's hypoth- 

 esis, matter is brought inward to the sun in 

 a dissociated condition ; produces intense heat 

 by its combustion at the solar surface; is then, 

 in a recombined state, projected into space by 

 the centrifugal force at the solar equator, again 

 to undergo the process of dissociation. The 

 indefinite continuance of these alternate proc- 

 esses is therefore an essential postulate in Dr. 

 Siemens's hypothesis. 



The theory here outlined may yet encounter 

 adverse criticism. The high standing, how- 

 ever, of its distinguished author and the ability 

 with which his views have been presented and 

 sustained have secured the earnest attention of 

 the scientific public. 



SUN-SPOTS AND AURORAS. The number of 

 sun-spots has been constantly increasing since 

 1878 ; and the maximum reached in 1882 has 

 indicated an extraordinary degree of solar ac- 

 tivity. The observations of the year have afford- 

 ed, moreover, a remarkable confirmation of the 

 theory that a connection of some kind exists 

 between sun-spots, auroras, and terrestrial mag- 

 netism. The size of some spots seen during 

 the year was enormous. On the 13th of April 

 one appeared on the eastern edge of the sun 

 which, before it reached the center of the disk, 

 attained a magnitude nin times greater than 

 the earth's entire surface. On the 14th of 

 April several small spots broke out a little in 

 advance of the great one. These rapidly in- 

 creased in size, so that on the 18th three spots 

 could be seen at the same time by the naked 

 eye a fact entirely unprecedented. Precisely 

 at the time of this great solar activity viz., 

 April 16th the most brilliant aurora of recent 

 times was seen throughout the United States, 

 while a violent magnetic storm was raging in 

 England and over the north of Europe. 



TOTAL ECLIPSE OF MAT 17ra. The expedi- 

 tion sent to Egypt by the British Government, 

 to observe the total eclipse of May 17th, was 

 eminently successful. At the meeting of the 

 Royal Society, on June 15th, Mr. Lockyer re- 

 ported the results obtained by Dr. Schuster 

 and himself, with their assistants, Messrs. 

 Woods, Lawrence, and Black. The duration 

 of totality was but seventy-two seconds ; yet 

 in this short time three photographs were 

 taken which show the corona to have had the 

 same form as that of 1871, but to have differed 

 in appearance from those of 1878 and 1867. 

 I't was accordingly inferred that the corona 

 varies with the sun-spots ; the eclipses of 1871 

 and 1882 having occurred at or near the maxi- 

 mum of solar activity, and those of 1867 and 

 VOL. xxii. 3 A 



1878 at the minimum. The unexpected dis- 

 covery of a comet close to the sun will again 

 be referred to. 



SOLAR PHENOMENA OBSERVED AT GREEN- 

 WICH. The new Astronomer Royal, Mr. W. 

 H. M. Christie, presented his first annual re- 

 port to the Board of Visitors on Saturday, 

 June 3, 1882. It is stated in this report that 



The sun's chromosphere had been examined with 

 the half-prism spectroscope on thirty-six days, and 

 on every occasion prominences were seen. On one 

 day a detailed examination of the whole spectrum of 

 the chromosphere was made at twenty-four points of 

 the sun's limb. Several prominences have shown 

 great changes in the course of two or three minutes, 

 and large displacements or contortions of the bright 

 lines, indicating very rapid motions of approach or 

 recession, have been noted. In particular, a promi- 

 nence examined on May 13, 1882, was observed to 

 rise through a space of about 30" in less than two 

 minutes, being at the rate of one hundred and ten 

 miles a second, while the C line showed a displace- 

 ment toward the red, gradually increasing from H to 

 11-4 tenth-metres, corresponding to a motion of re- 

 cession increasing in two minutes from thirty-six to 

 three hundred and thirty miles a second. 



As observed at Greenwich, the sun's disk 

 was found free from spots on only two days 

 during the year ending May 20, 1882. 



In a communication to "Nature," dated Oc- 

 tober 5, 1882, Mr. Christie, the Astronomer 

 Royal, gives a statement of facts in regard to 

 the simultaneous occurrence of large and nu- 

 merous sun-spots, a magnetic storm, and a 

 brilliant aurora borealis on the 1st and 2d of 

 October. The largest sun-spot of this date 

 covered an area five times greater than the 

 earth's surface. 



NEW METHOD OF FINDING THE SUN'S DIS- 

 TANCE. Mr. T. S. H. Eytinge, of Cainsville, 

 Canada, has suggested a new method of deter- 

 mining the velocity of light, or, what amounts 

 to the same thing, of finding the distance of 

 the sun from the earth. The rate at which 

 light travels has been ascertained approximately 

 by observations of Jupiter's satellites, and also 

 by carefully conducted optical experiments. 

 Mr. Eytinge proposes a third method, namely, 

 by observations of variable stars. It is well 

 known that certain variables of short period 

 have regular intervals of fluctuation. If, then, 

 these intervals be accurately determined, and 

 also the changes produced in their values by 

 the earth's orbital motion, we shall have the 

 time which light requires to cross the earth's 

 orbit. Mr. Eytinge says he has tested his 

 method, and that he hopes in due time to make 

 known his results. 



PROFESSOR LANGLEY'S MOUNT WHITNEY OB- 

 SERVATIONS. Professor Langley's experiments 

 at the Alleghany Observatory having rendered 

 it probable that the amount of heat radiated 

 by the sun had been underestimated by pre- 

 vious observers, it became desirable to verify 

 these results by simultaneous observations at 

 the base and summit of a very high mountain. 

 Accordingly, with the co-operation of General 

 W. B. Hazen, the head of the United States 



