534 THE POPULAR SCIENCE MONTHLY, 



We must, then, look at the sun with no more idea of witnessing 

 any thing without the sphere of natural laws, than in looking at a fire 

 across the street. It need not follow that we shall find the operation 

 of those laws exactly the same that our limited experience has pre- 

 sented, and we shall still find abundant cause for admiration and won- 

 der without introducing mysteries of our own creation. 



When we telescopically examine that brilliant surface which we 

 see daily with the naked eye (the photosphere), to study such of its 

 phenomena as are here described, we do not need the spectroscope, 

 but some means of protecting the eye from the blinding light and 

 heat, and this should not involve the use of any colored shades. If 

 we look into an unsilvered glass, as, for instance, into the panes of a 

 shop-window from the street, we observe that it acts as a mirror, 

 sending back a feeble reflection of ourselves, or other objects without ; 

 most of the rays from which have gone altogether through the glass, 

 while a comparative few are returned to form the image. It may 

 occur to us, then, instead of looking directly at the solar image formed 

 by our telescope, to let it fall on a piece of plain glass, placed diag- 

 onally, through which about nineteen parts in twenty of the light will 

 pass and be thrown away, the remaining twentieth being reflected and 

 forming an exact though enfeebled image. 



When this has been done, if the reflected image be still too bright, 

 we may reflect it aga^'n, this time only a twentieth of the first twen- 

 tieth reaching the eye, and so on to any degree ; but it is strikingly 

 illustrative of the intensity of the solar splendor that, when, by three 

 such reflections, the sunlight has been enfeebled 8,000 times, we yet 

 find it intolerably bright. Instead of more mirrors, it is better to now 

 arrange that the third mirror may rotete, so as to polarize the light. 

 When this is done, the image of the sun appears distinct (if the optician 

 have done his work well), colorless, and of any brightness desired. 



The instrument just described in general terms is known as the 

 polarizing eye-piece. All danger and discomfort in studying the sun 

 disappear with its use, and we may look at its unclouded face as 

 though the eye had been strengthened to bear its light ; in fact, many 

 hours of scrutiny of the solar disk with this instrument wearies the 

 eye less than a few minutes' telescopic examination of the moon does 

 without it. 



What we shall see with it is far from being that sphere of dazzling 

 light, everywhere equally brilliant, which we have been accustomed to 

 consider the sun. The eye ranges over a vast surface, presenting at 

 one view over five thousand times the entire area of our globe, to find 

 everywhere diversity of shade. It is not only darker near the edges 

 than at the centre, but the whole (apart from any consideration of the 

 spots) presents an appearance somewhat lil<e that very peculiar one 

 which the ocean has when we obtain a bird's-eye view of it from some 

 great height. 



