282 i/r. H. F. Newall [Feb. 9 



show jou some illustrations of the records got during the last eclipse, 

 and then we can dig up the seeds and see whether any seedlings are 

 recognisable. 



First of all, with respect to changes in the corona and the ques- 

 tion of the rotation of the corona, we know that in the brief 

 moments of even the longest eclipse of the sun these changes have 

 hitherto been nearly, if not completely, inappreciable ; but we know 

 also that the form changes from year to year, and so we are con- 

 vinced that if sufficiently delicate precautions are taken in getting 

 the records the change should be detected in the lapse of the few 

 hours that pass between the observations which are made at widely 

 separated stations along the track of the shadow of the moon in any 

 given eclipse. 



What the nature of the change is, it is rather difficult to surmise. 

 Is it of the nature of a rotation of these streamers about the axis of 

 rotation of the sun ; or is it rather a change which might be described 

 as involving the dying out of some of the streamers and the sudden 

 protrusion of others from the sun ? Or are we rather to take these 

 streamers as not thrust out from the sun at all ? Are they effects 

 which are produced in the matter which the sun finds in his passage 

 through space ? It may be that the curved outlines of the chief 

 streamers which we see coming from the sun are envelopes, mathe- 

 matically speaking, or surfaces formed by the intersection of multi- 

 tudinous straight rays, seen in perspective. Or it may be that they 

 are the paths of emanations — something thrust out from the sun 

 and passing outward under the influence of various forces of rela- 

 tively changing magnitude. 



We know how meteorites fall on the earth as she moves through 

 space, for we see them leave luminous trails as they rush through 

 our atmosphere. We realise how they may be splintered into small 

 fragments in passing through the air. The sun must meet many 

 more m(;teorites than does the earth. Again, we know how comets 

 move round the sun, and how they emit gas and vapour as they 

 approach tlie sun ; and we can guess how the scorching influence of 

 tlie sun, as the comet hurries through its immediate neighbourhood, 

 results in the splitting up of the small stones of which the head of 

 the comet is mainly composed ; ruins of dust and vapour are left 

 behind, and it is in the midst of this dust and vapour that the sun 

 moves. 



Then, we are taught by Clerk Maxwell's bold imaginings and 

 calculations that where there is light there must be pressure of radia- 

 tion. A body brought into the light must inevitably experience 

 pressure of radiation, resulting from the falling of the light upon it, 

 and partly connected with the shadow which the body casts behind it, 

 there being light on one side and darkness on the other. The radia- 

 tion falls on the body only on one side. Lebedew and, again, Nichols 

 and Hull have shown us experimentally that this pressure of radia- 



