244 Th e Eclipse of Last December. [April, 



is not available. Fortunately we have an explanation, and, 

 carefully considered, it throws some light on an interesting 

 question of solar physics. Mr. Brothers tells us that there 

 was a good deal of wind during totality. Now the image of 

 moon, prominences, and corona being more swayed in a 

 horizontal than in a vertical direction, we can understand 

 that the moon's horizontal diameter would be more affected 

 than the vertical diameter. The aclinic energy of the 

 prominences far exceeds that of the corona, so that the 

 prominences would leave their track (as it were) un- 

 mistakably impressive on the eastern and western limbs of 

 the moon. But it needs only a brief study of the picture 

 to see that the western limb has suffered much more than 

 the eastern. At first sight this seems perplexing, especially 

 when we note that the whole of this limb has suffered, not 

 such parts only as were opposite lofty prominences. But 

 when we consider that the totality was drawing to a close 

 at the time, we see that this is precisely what should be 

 expected ; for the sierra would have come into view on the 

 western side, while the sierra on the eastern side would be 

 concealed by the advancing moon. It was the image of the 

 sierra, then — swayed backwards and forwards by the wind 

 across the western limb of the moon — which caused the 

 remarkable flattening of the moon on that side.* 



The second feature is the great extent both of the inner 

 and outer corona on the western side. Now, as respects 

 the inner corona, a portion of the excess of width on the 

 western side must, without doubt, be ascribed to the flattening 

 of the western side of the moon's disc. We have only to 

 conceive the full dimensions of the moon indicated on that 

 side to see that the inner corona there will be greatly reduced. 

 Since, also, the moon was as far as possible towards the 

 east — for it is to be remembered that 3 s - after the exposure 

 was completed totality ended — we seem to have a sufficient 

 explanation of the eccentricity of the ring-formed corona. 

 As regards the great extension of the outer corona towards 

 the west, it is necessary to note that the outer corona even 

 in the negative is of extreme delicacy, — very much more 



* We have corroboratory evidence on this point in Father Secchi's account 

 of the eclipse. For he tells us that towards the close of the totality he was 

 able to see the protuberances (at first there had been clouds) ; and he remarks 

 that the protuberances formed a beautiful small semicircular corona. "It was 

 full of the well-known rosy jets, of admirable shape and beauty," confirming 

 the view that " they extend all round the sun, differing in height in different 

 places." It will be seen that Father Secchi considers the evidence altogether 

 unfavourable to the existence of a real envelope such as that conceived in the 

 theory embodied in the title chromosphere (for the sierra.) 



