Astronomical Lectures. 



searches will throw important light ou the coudi- 

 tioii of the sun. 



SOLAR PROMINENCES AND CORONA. 



It was observed that the spots waxed and waned 

 in number over the surface of the sun, and alter brilf 

 a century of research, that the spots increase and 

 diminish (until they disappear altogether), and that 

 the period within which they waxed and wane is 

 about eleven of our years. After that was discov- 

 ered, it was noted that the magnetic influences of the 

 earth waxed and waned in about the same time. The 

 magnetic needle which points in England to west 

 of north, in this country not to due north, has 

 a swaying motion as if endeavoring t<> move to- 

 ward the sun. That motion undergoes varia- 

 tions, sometimes greater and sometimes less, 

 and physicists watched, and they found that in 

 about eleven years the swaying of the magnetic 

 needle, which was so insignificant us to seem diffi- 

 cult of detection, undergoes a slight change which 

 corresponds with the number of spots on the sun. 

 When the spots are greatest it has its greatest sway, 

 and when the spots are fewest it has the least sway. 

 The aurora also was associated with the sun. But 

 further evidence of these influences was needed, and 

 it came in 1859, when a bright spot suddenly made 

 its appearance on the sun, and it was found that the 

 Bslf-recerding magnetic needle at Kew made certain 

 jumps at the same instant ; auroras appeared in both 

 hemispheres, and everything proved that at that 

 moment the sun had given out magnetic influences, 

 not to our earth alone, but doubtless to Mercury and 

 Venus and Mars, then to the asteroids and to Jupiter 

 and Saturn. Anew bond of harmony had been found 

 within the solar system. 



[A photographic picture representing prominences 

 011 the sun was here exhibited.] 



In 1842 these were looked upon as belonging to the 

 atmosphere of the moon, but they were proved in 

 1868 to belong to the sun. They were like garneta 

 around a brooch of jet, and these were found to be 

 actually existing on the surface of the sun. What 

 were they? During the eclipse of 1868 that question 

 was answered, and it was found that they are not 

 flames or mountains, but masses of glowing hydro- 

 gen. It was by the spectroscope that it was discov- 

 ered. Consisting of glowing gas, they would give 

 Btich lines as these, and the four lines of the gas 

 hydrogen were recognized. 



A curious experiment will be produced by glow- 

 Ing hydrogen. Tubes are filled with hydrogen under 

 a low pressure corresponding to the pressure which 

 is believed to exist on the prominences of the sun, 

 and yon will have the true color of these promi- 

 nences, shining with the true light of glowing 

 hydrogen. 



[An exceedingly brilliant experiment was hero 

 made, the hydrogen appearing to glo\v brightly 

 even with all the lights in the room in fall blaze, 

 and showing an exact imitation of the solar promi- 

 nences.] 



A new method of research was applied ; it was now 

 known that the flames shone with a light that could 

 be divided into separate lines in the day time. Tho 

 spectroscope spread out these lines; they were 

 visible. It was found even possible to see the promi- 

 nences themselves. 



[A picture of the sun's chromosphere was uext 

 produced.] 



THE CHROMOSPHERE. 



This ruddy matter around the sun is called tho 

 chromosphere. You will presently see injected into 

 it a still more ruddy matter, as if there was an ex- 

 plosion on the surface of the sun. [A bright crimson 

 mass was here shot through the chromosphere and 

 slowly fell back. The audience applauded vigor- 

 ously.] Processes such as this have been watched, 

 and have taken place on the surface of the sun, be- 

 fore the eyes of observers. Another of these experi- 

 ments will be made for you by Prof. Morton's assist- 

 ant, Mr. Wale. In this picture you see the whole 

 fieid covered with ruddy matter, and this corre- 

 sponds with diagrams of real pictures taken by as- 

 tronomers. 



ERUPTION PROMINENCES. 



First sta?e of a prominence observed byZolliierat lOb. 22m., An?. 29 

 1860. Hight about 45,000 miles. 



In this picture you see the explosion just as if a 

 rocket was sent up, and here, in the next picture, 

 one hour later, the upper part of the eruption sink- 

 ing back to the surface of the sun. The next picture 

 is one taken at the Cambridge Observatory. Nothing 

 is clearer than that here some matter has bee3 

 thrown lorth from the sun. Here is a ruddy cascade 



