438 Chronicles of Science. [July, 



which do not differ greatly from those which belong to the surface of 

 our earth. But the phenomena in our sun are so entirely different 

 from any that we experience, and perhaps from any that we can con- 

 ceive, that we must be exceedingly careful in our conclusions regard- 

 ing them, that we may not be mistaken. We must throw away all 

 speculation and hypothesis, and submit to be guided by observation 

 alone. The luminous disc or surface of the sun is termed its pho- 

 tosphere, and inquiry with reference to this surface may be divided 

 into three parts : the first, relating to the region above the photo- 

 sphere ; the second, to the photosphere itself ; and the third, to the 

 region below the photosphere. 



To commence with the region above the photosphere, it is easy to 

 show that it contains a very dense atmosphere which is of a com- 

 paratively low temperature. In the first place, according to a well- 

 known law, the dark lines in the solar spectrum denote the presence 

 of certain substances in the state of vapour, and yet in a comparatively 

 cold state above the photosphere of the sun. These substances 

 comprise, amongst others, sodium, magnesium, iron, and nickel. 



Another proof of the existence of a solar atmosphere is that the 

 light from the border is less intense than that from the centre of the 

 disc ; this is due to the fact that the light from the border has to 

 pierce through a much greater depth of atmosphere than light from 

 the centre, and hence a great portion of the light from the border will 

 be absorbed by this atmosphere if it be colder than the source of light. 

 The last proof of an atmosphere is that derived from the picture of 

 the sun taken during a total eclipse. At the lecture some of Mr. De 

 la Rue's celebrated eclipse photographs were projected on to the 

 screen by means of the electric lantern, and the images of the corona 

 and " red flames " were in this way exhibited to the audience. These 

 photographs showed that as the moon proceeded over the sun's disc, 

 the red flames and part of the corona discovered themselves at that 

 side which she had left, and were covered up by her disc at that side 

 towards which she was approaching ; thus showing that they be- 

 longed to the sun. 



Next, with regard to the photosphere, the first thing to be noticed 

 is the fact that this is not a smooth, uniform, continuous surface. 

 When it is viewed through powerful glasses, it appears granulated or 

 mottled. But this is not all ; there is reason to believe that great 

 magnifying and defining power shows us something more, although 

 it is very difficult to see it. Mr. James Nasmyth was the first to 

 proclaim the curious fact that the wholo photosphere of the sun is 

 made up of detached bodies interlacing one another, and preserv- 

 ing a great amount of regularity both in form and size ; he called 

 them ivillow leaves ; Mr. Stone has called them rice grains ; Father 

 Secchi coups-de-pinceau. It wotdd be a speculation much beyond our 

 power to conjecture what it is that gives these bodies their astonish- 

 ing regularity of form. The lecturer then drew attention to the 

 brighter portions of the photosphere, or facuke, as they are sometimes 

 called. It is chiefly near the edge of the sun that these relatively 

 bright portions of the sun's disc appear, for when they come to the 



