SCINTILLATION OF THE STARS. 103 



nature of a celestial body. Although well versed in the 

 science of optics, in its then imperfect state, he was unable 

 to rise above the received notion of moving vapours. 4 * In 

 the Chinese Records of the newly appeared stars, according 

 to the great collection of Ma-tuan-lin, their strong scintillation 

 is occasionally mentioned. 



The more equal mixture of the atmospheric strata, in 

 and near the tropics, and the faintness or total absence of 

 scintillation of the fixed stars when they have risen 12 or 

 15 above the horizon, give the vault of heaven a peculiar 

 character of mild effulgence and repose. I have already 

 referred in many of my delineations of tropical scenery to this 

 characteristic, which was also noticed by the accurate ob- 

 servers, La Condamine and Bouguer, in the Peruvian plains, 

 and by Garcin,** in Arabia, India, and on the shores of the 

 Persian Gulf (near Bender Abassi). 



As the aspect of the starry heavens, in the season of 

 the serene and cloudless nights of the tropics, specially 

 excited my admiration, I have been careful to note in my 

 journals the height above the horizon at which the scin- 

 tillation of the stars ceased in different hygrometric con- 

 ditions. Cumana and the rainless portion of the Peruvian 

 coast of the Pacific, before the season of the garua (mist) 

 had set in, were peculiarly suited to such observations. On 

 an average the fixed stars appear only to scintillate when less 

 than 10 or 12 ab^ve the horizon. At greater elevations, 

 they shed a mild, planetary light; but this difference is 

 most strikingly perceived, when the same fixed stars are 

 watched in their gradual rising or setting, and the angles of 

 their altitudes measured, or calculated by the known time and 



** Causa scintillationis, in Kepler, De Stella nova in pede 

 Serpentarii, 1606, cap. xviii. pp. 9297. 



46 Lettre de M. Garcin, Dr. en Med. a M. de Reaumur in 

 Hist, de VAcademie Royale des Sciences, Annee 1743, pp. 

 28-32. 



