537 



NOTES TO THE FOURTH BOOK. 



NOTE A. 



The end of the eclipse of the Sun, on the 28th of October, 

 1799 (Chapter X, p. 312 of this volume), presented me with 

 a very remarkable phenomenon, which I shall describe, as I 

 find it noted in my Astronomical Journal. " Looking 

 through Dollond's large achromatic telescope very steadfastly 

 (at 4h 58' by the chronometer) at the darkened part of the 

 Sun's disk, I saw three or four luminous dots, appear and 

 disappear successively. They were like stars of, the fifth 

 magnitude. I thought for some moments, that this pheno- 

 menon was owing to the explosion of volcanoes in the moon, 

 the existence of which is admitted by Herschell, but which 

 Don Antonio Ulloa considers as holes, that pass through the 

 planet. What was my astonishment, when, toward the end 

 of the eclipse, at 5 h 37' by the chronometer, I perceived two 

 similar luminous dots beyond the disk, at an arc of twelve or 

 fifteen minutes distance from the limb which had not been 

 eclipsed ! The eclipse ended at 5 h 48 / 37* by the chronom- 

 eter. These two luminous dots appeared only once. Their 

 light was of the intensity of a star of the third magnitude. 

 I could not explain to myself this appearance. My eye was 

 not at all fatigued.' 



Louville relates (Mem. de VAcad., 1715, p. 96) having seen 

 at London, during the total eclipse of the Sun on the 3d of 

 May, 1715, " fulminations, or instantaneous vibrations of 

 luminous rays. They appeared, during the total darkness, 

 on the surface of the moon, so that I thought I saw trains of 



