202 Mr. William Huggins [Feb. 20, 



WEEKLY EVENING MEETING, 



Friday, February 20, 1885. 



Sir Frederick Bramwell, F.R.S. Manager and Vice-President, 

 in the Chair. 



William Huggins, Esq. D.C.L. LL.D. F.E.S. M.B.L 



On the Solar Corona. 



If it were usual to prefix a motto to these evening discourses, I might 

 have selected such words as " Seeing the Invisible," for I have to 

 describe a method of investigation by which wliat is usually unseeable 

 may become revealed. We live at the bottom of a deep ocean of air, 

 and therefore every object outside the earth can be seen by us only as it 

 looks when viewed chrough this great depth of air. Professor Langley 

 has shown recently that the air mars, colours, distorts, and therefore 

 misleads and cheats us to an extent much greater than was sui3j)osed. 

 Langley considers that the light and heat absorbed and scattered by 

 the air and the particles of matter floating in it amount to no less than 

 40 per cent, of the light falling upon it. In consequence of this want of 

 transparency and of the presence of finely divided matter always more 

 or less suspended in it, the air, when the sun shines upon it, becomes 

 itself a source of light. This illuminated aerial ocean necessarily 

 conceals from us by overpowering them any sources of light less bril- 

 liant than itself which are in the heavens beyond. From this cause 

 the stars are invisible at midday. This illuminated air also conceals 

 from us certain surroundings and a|)pendages of the sun, which become 

 visible on the very rare occasions when the moon coming between us 

 and the sun cuts ofi" the sun's light from the air where the eclipse is 

 total, and so allows the observer to see the surroundings of the sun 

 through the cone of unilluminated air which is in shadow. It is only 

 when the aerial curtain of light is thus withdrawn that we can become 

 spectators of what is taking place on the stage beyond. The mag- 

 nificent scene never lasts more than a few minutes, for the moon 

 passes and the curtain of light is again before us. On an average, 

 once in two years this curtain of light is lifted for from three to six 

 minutes. I need not say how difficult it is from these glimpses at 

 long intervals even to guess at the plot of the drama which is being 

 played out about the sun. 



The purjiose of this discourse is to describe a method by which it 

 is possible to overcome the barrier presented to our view by the 

 bright screen of air, and so watch from day to day the changing 

 scenes taking place behind it in the sun's surroundings. 



