SCINTILLATION OF THE STAKS. 105 



season is announced many days beforehand, by a flickering 

 light of the stars at great altitudes above the horizon. This 

 phenomenon is accompanied by sheet lightning, and single 

 flashes on the distant horizon, sometimes without any visible 

 cloud, and at others darting through narrow, vertically ascend- 

 ing columns of clouds. In several of my writings I have 

 endeavoured to delineate these precursory characteristics and 

 physiognomical changes in the atmosphere. 46 



The second book of Lord Bacon's Novum Organum giva, 

 us the earliest views on the velocity of light and the pro- 

 bability of its requiring a certain time for its transmission. 

 He speaks of the time required by a ray of light to traverse 

 the enormous distances of the universe, and proposes the 

 question whether those stars yet exist which we now see 

 shining. 47 We are astonished to meet with this happy con- 



46 See Voyage aux Regions equin., t. i. pp. oil and 512, 

 andt. ii. pp. 202-208; also my Views of Nature, pp. 16, 138. 



" En Arabic, de meme qu'a Bender- Abassi, port fameux du 

 Golfe Persique, 1'air est parfaitement serein presque toute 

 f annee. Le printemps, 1'ete, et 1'automne se passent, sans 

 qu'on y voie la moindre rosee. Dans ces memes temps tout 

 le monde couche dehors sur le haut des maisons. Quand on 

 est ainsi couche, il n'est pas possible d'exprimer le plaisir qu'on 

 prend a contempler la beaute du ciel, 1'eclat des etoiles. (Test 

 une lumiere pure, ferme et eclatante, sans etincellement. Ce 

 n'est qu'au milieu de 1'hiver que la scintillation, quoique tres 

 foible, s'y fait apercevoir.*' 



"In Arabia," says Garcin, "as also at Bender-Abassi, a 

 celebrated port on the Persian Gulf, the air is perfectly serene 

 throughout nearly the whole of the year. Spring, summer, 

 and autumn, pass without exhibiting a trace of dew. During 

 these seasons all the inhabitants sleep on the roofs of their 

 houses. It is impossible to describe the pleasure experienced 

 in contemplating the beauty of the sky, and the brightness 

 of the stars, while thus lying in the open air. The light of 

 the stars is pure, steady, and brilliant ; and it is only in the 

 middle of the winter, that a slight degree of scintillation is 

 observed.'' Garcin, in Hist, de I Acad. des Sc., 1743, p. 30. 



47 In speaking of the deceptions occasioned by the velocity of 



