RAYS OF THE STAES. 173 



clined. 40 Some of my astronomical friends see three, or at 

 most four rays above, and none below the star. It has always 

 appeared extraordinary to me, that the ancient Egyptians 

 should invariably have given only five rays to the stars (at 

 distances, therefore, of 72) ; so that a star in hieroglyphics 

 signifies, according to Horapollo, the number five. 41 



The rays of the stars disappear when the image of .the radiat- 

 ing star is seen through a very small ,aperture made with a 

 needle in a card, and I have myself frequently observed both 

 Canopus and Sirius in this manner. The same thing occurs in 

 telescopic vision through powerful instruments, when the stars 

 appear either as intensely luminous points, or as exceed- 

 ingly small discs. Although the fainter scintillation of the 

 fixed stars in the tropics conveys a certain impression of 

 repose, a total absence of stellar radiation would, in my 

 opinion, impart a desolate aspect to the firmament, as seen by 

 the naked eye. Illusion of the senses, optical illusion, and 

 indistinct vision, probably tend to augment the splendour of 

 the luminous canopy of heaven. Arago long since proposed 



owing to the imperfect construction of the instrument (to the 

 different curvatures of the two sides of the object-glass), and 

 to certain defects and aberrations pertaining to the eye itself. 

 The smaller the star appears, the more perfect is the instru- 

 ment, providing all relations are equal as to the diameter of 

 the object-glass, the magnifying power employed, and the 

 brightness of the star. Now -the best means of judging 

 whether the stars are very small, and whether the points are 

 represented in the focus by simple points, is undoubtedly that 

 of directing the instrument to stars situated very near each 

 other, and of observing whether the images of known double 

 stars are confused, and impinging on each other, or whether 

 they can be seen separate and distinct." (Arago, M.S. of 

 1834 and 1847.) 



' Hassenfratz, Sur les rayons divergens des Etoiles in 

 Delametherie, Journal de Physique, torn. Ixix. 1809, p. 324. 



41 Horapollinis Niloi Hierogtyphica, ed. Con. Leemans, 



