XCV111 NOTES. 



tion of solar spots merely say that the sun's disk, which indicates good 

 weather, shows no diversity of surface, nothing that marks it (ju/jSe n 

 oTj/ua Qepot), but rather perfect uniformity. The<njjwa, or chequered surface, 

 is, moreover, expressly attributed to light cloud, belonging to the vapours 

 of our atmosphere (the Scholiast to Aratus says, the " thickness of the 

 air") : hence it is always the morning or the evening sun which is referred 

 to, and which, quite independently of true solar spots, may certainly serve 

 as diaphanometers, and are still regarded, both by sailors and agriculturists, 

 according to an opinion by no means worthy of being despised, as afford- 

 ing useful indications of approaching changes of weather. The sun's disk, 

 when near or on the horizon, is seen through the lowest atmospheric 

 strata. Of the large solar spots which were seen by the naked eye in the 

 years 807 and 840, and erroneously supposed to be transits of Mercury and 

 Venus, the first was recorded in the great historic collection of Justus 

 Reuberus, Veteres Scriptores (1726), in the part entitled Annales Regum 

 Fraucorum Pipini Karoli Magni et Ludovici a quodam ejus setatis Astronomo, 

 Ludovici regis domestico, conscripti, p. 58. The authorship of these Annals 

 was first attributed to a Benedictine monk (p. 28), and afterwards, and more 

 correctly, to the celebrated Eginhard (Einhard, Charlemagne's private secre- 

 tary) : see Annales Einhardi, in Pertz's Monumenta Germanise historica, 

 Script. T. i. p. 194. The passage referred to is the following : " DCCCVII. 

 stella Mercurii xvi. Kal. April, visa est in Sole qualis parva macula nigra, 

 paululum superius medio centro ejusdem sideris, qua a nobis octo dies con- 

 spicata est ; sed quando primum intravit vel exivit, nubibus impedientibus, 

 minime notare potuimus." The passage respecting the supposed transit of 

 Venus mentioned by Arabian astronomers, is given by Simon Assemannus in 

 the Introduction to the " Globus coelestis Cufico-Arabicus Veliiferni Musei 

 Borgiani," 1790, p. xxxviii., and is as follows: "Anno Hegyrse 225, 

 regnante Almootasemo Chalifa, visa est in Sole prope medium nigra qusedam 

 macula, idque feria tertia die decima nona Mensis Regebi . . . ." It was 

 believed to be the planet, and that the same macula nigra (therefore with 

 interruptions of 12 or 13 days) was seen for 91 days. Soon afterwards 

 Motassem died. I subjoin 17 instances, taken from a larger number col- 

 lected by me, of historical or traditional accounts of suddenly-occurring 

 diminutions or obscurations of the light of day : 



Anno 45 B.C., at the time of the death of Julius Caesar, after which 

 the sun was for a whole year paler, and gave less heat than usual, so 



