ON THE PERIODICITY OF THE AURORA BOREALIS. 307 



11, 17, 18'. 21«, 22, 23, 26; April 13, 18, 21 (et Australis), 28; May 9, 12 (placida), 13, 15 (magna, 

 placida) ; June 5, 8, 16, 17, 23 ; July 10, 15 (magna), 16, 21 ; Aug. 7 ; Sept. 16 (tranquilla) ; Oct. 6, 12-, 

 17, 18 ; Nov. 4» (magna, placida, ab liora 5), !• ; Dec. 31. 



1739. Jan. 18; Feb. 1- ; March 11-, 12-, 13-, 20, 28, 29- (maxima); 1 April 5- (exigua), 14, 15, 19, 29- 

 (placida sed magna) ; May 1«, 2; 3, 4-, 5 (magna), 6, 8, 9, 10, 11, 12 ; June 2- (magna, comscans), 5, 23 

 (tenuis) ; July 6 (placida. magna), 7, 12, 15, 28, 31 ; Aug. 1, 6, 7, 10-, 12-, 13, 28; Sept. 1 (tenuis), 8-, 10, 

 23- (magna), 24- (coruscans), 28- ; Oct. 3- (parva), 9 (magna, placida), 24- (magna, coruscans), 25- (magna) ; 

 Nov. 21. 



1740. Jan. 30- ; March 23-. 



1741. Jan. 20-, 21', 22, 23- (coruscans, magna) ; 2 Feb. 3, 6, 16- ; March 11-, 12-, 13-, 16- (magna), 29 

 (meridionalis) ; 3 April 9-, 13-, 16-, 30 ; May 7, 8, 9, 10, 12, 15, 18, 30 ; Aug. 10- (coruscans),- 13-, 20« (magna, 

 coruscans), 22-, 31; Sept. 1, 3, 4, 12 (coruscans), 19-, 20; Oct. 2- (coruscans), 8; 13- (placida), 14% 15- 

 (coruscans), 28- ; Nov. 2-, 12-, 28. 



1742. Jan. 13, 14, 23, 29- ; Feb. 12, 13 ; March 13«, 28 ; April 2-, 3, 8, 10-, 24, 29, 30 ; Oct. 27- (magna) ; 

 Dec. 28. 



1743. Jan. 1, 3-, 19 ; March 19- (magna, corusca), 20-, 24-, 26-, 30 ; Aug. 9, 12 ; Sept. 8, 9, 18- ; Oct. 7: 



1744. April 2; 5, 13, 17 ; May 5, 16, 27 ; July 16, 17. 



1745. Jan. 10 ; Feb. 4, 8 ; April 18, 19, 28 ; May 19, 30 ; Aug. 2. 



1746. Jan. 26 ; Feb. 26- ; March 19, 25- (magna), 26 ; April 14, 17, 18, 20, 21 ; May 7, 12 (magna), 16 

 (magna), 17, 26 ; July 14, 20, 22 ; Aug. 20, 21, 25 ; Oct. 22. 



1747. Jan. 6-, 8-, 9-, 10-, 11; Feb. 1, 7-, 16; April 2- (magna), 3-, 5, 9, 10, 13, 29, 30; May 2 ; July 18; 

 Aug. 4, 8; Sept. 6, 10-, 13, 14, 27-; Oct. 1, 2; 3, 5, 9-; Nov. 28; Dec. 3-, 17- (magna), 18-, 22, 27 (magna). 



'1748. Jan. 6-, 7, 20, 29 ; Feb. 3-, 27- ; March 3, 5 ; April 24, 20 ; May 1-, 2, 12, 21 ; June 3- ; July 17, 

 22 ; Aug. 1 ; Sept. 11-, 23- ; Oct. 12 ; Dec. 16-, 18-, 24-. 



1749. Jan. 10, 18, 23 ; Feb. 11- ; March 6, 7, 11-, 28- ; April 22 ; May 10-; July 8, 9, 11, 12 ; Aug. 15, 

 20; Sept. 22-; Nov. 10. 



1750. Jan. 3, 6- (magna) ; Feb. 3- 4 (magna), 7; 12, 27- (magna) ; March 4- (placida), 9-, 11-; April 5, 



1 Die 29° per totam noctem coruscavit Aurora Borealis, expansa per universutn caelum, aeque in parte australe quam 

 boreale, cum columnis subinde ruberrimis, diu perstantibus, praeeipue australibus : illuminabat vehementer terram, veluti 

 luna dividua illuminare solet : atrae interruptae nubes in plaga boreale caeli : super has lux candidior erat. 



2 Die 23°, noctu, magna, coruscans Aurora Borealis elabitur in plaga orientali, et extenta usque ad austrum ; non 

 vero in septentrionali plaga aliquid lucentis phaenomeni conspectum fait; quatuor se exequentibus noctibus fulsit Aurora 

 Borealis, sed placida fuit tribus primis noctibus, douec quarta nocte ardere visa merit, columnasque jaculari ingentes. 



' Sed die 29°, fuit Aurora meridionalis in plaga solstitii Aestivi orieutalis usque ad meridiem. Luna fere erat plena, 

 et fulgebat clare in caelo: hinc videri non potuisset nisi fuisset coruscans. Sed locus sub ilia prope horizontem clarissima 

 luce micabat. Pars caeli borea lucis hujus omnino expers fuit 



' Mense Februario fulserunt quatuor Aurorae Boreales magnae : praeeipue die 3°, quae admodum rubra et coruscans : 

 verum 27° die, hora 9i vespertina, erat insignis, quae totam plagam caeli boream occupabat, quamvis non vibrans colum- 

 nas. Quod singulare in ea, distabat ab aurora tractus longus lucidus, ab horizonte ortivo ad occasum extensus, non 

 majori sub latitudine quam arcus caelestis, transiens inter Ursam Majorem et Orionem, ferebatur lente ad austrum, quia 

 spirabat corus, postea hinc inde inflectpb.atur, instar serpentis, mox a vento frangebatur in partes : hora 104 jam erat 

 lumen mutatum, propulsum ad austrum, atque a materie nubis borealis magna copia expulsa ad austrum fuit, adeo ut 

 caelum ab omni parte lumine boreo impleri coeperit : hie tractus cumulabatur iu trabem, quae caeli fornicem sustentaret : 



