ON THE SOLAE ECLIPSE OF DEC. 13, 1871. 333 



Sketches. 



From the photographs, in which the corona is depicted actinically, we pass 

 to the drawings, in which it is depicted visually. I would first call attention 

 to two drawings made by Mr. Holiday, who formed part of the expedition, 

 and in whose eye every one who knows him will have every confidence. 



First, there is a drawing made at the commencement of the totality, and 

 then a drawing made at the end. There is a wonderful difference between 

 these drawings ; the corona is in them much more extensive than it is repre- 

 sented actinically on our plates. 



In another drawing, made by Captain Tupman, we have something abso- 

 lutely different from the photographs and from Mr. Holiday's sketches, inas- 

 much as we get an infinite number of dark lines and a greater extension 

 than in the photographs, though in the main the shape of the actinic corona 

 is shown. 



The corona, as it appeared to me, was nothing but an assemblage of such 

 bright and dark lines ; it lacked all the structure of the photographs, and 

 appeared larger ; and I have asked myself whether these lines do not in some 

 way depend on the size of the telescope or the absence of a telescope. It 

 seems as if observations of the corona with the naked eye, or with a telescope 

 of small power, may give us such Knes ; but that when we use a telescope of 

 large power it will give, close to the moon, the structure to which I have 

 referred, and abolish the exterior structure altogether, leaving a ring round 

 the dark body of the moon, such as Prof. Respighi and myself saw in our 

 trains of prisms, and I in the 6|-inch telescope, in which the light was reduced 

 by high magnification so as to bring the corona to a definite ring some 5' 

 high, while Prof. Respighi, using a 4-inch telescope, brought the corona down 

 to a ring something like 7' high. 



Many instances of changing rays, like those seen by Plantamour in 1860, 

 were recorded by observers in whom I have every confidence, one observer 

 noting that the rays, revolved and disappeared over the rifts. 



Polariscopic Observations. 



Mr. Lewis, in sweeping round the corona at a distance of some 6' or 7' from 

 the sun's limb, using a pair of compensating quartz wedges as an analyzer, 

 which remained parallel to itself when the telescope swept round, observed 

 the bands gradually to change in intensity, then disappear, bands of a com- 

 plementary character afterwards appearing, thereby indicating radial polari- 

 zation. 



Dr. Thomson, at Bekul, saw strong traces of atmospheric, but none of 

 radial polarization, with a Savart. With the same class of instrument the 

 result obtained by myself was precisely similar ; while on turning in the 

 Biquartz, at the top and bottom of the image of the corona, i. e. near the 

 sun's equator, faint traces of radial polarization were perceptible for a short 

 distance from the moon's limb. Captain Tupman, who observed with the 

 polariscope after totality, announces strong radial polarization extending to a 

 very considerable distance from the dark moon. 



Reversal of Lines at beginning and end of Totalitg. 



Captain Maclear, who was observing with me at Bekul for some time just 

 before the commencement of totality, but when the light of our atmosphere 

 was cut off by the interposition of the dark moon, saw a large number of very 

 fine lines of difierent heights at the base of the chromosphere. 



