108 



ON THE SECULAR PERIODICITY OF THE AURORA BOREALIS 



and November 2, 1730 



December 29, 1736; on April 21, 1750 



August 6 



1768 ; and on July 19, 1769 ; descriptions of which have already been published. I 

 have selected from the unpublished manuscripts already mentioned all those examples 



* 



of auroras which are described as red, or bright, or high, or great, or considerable, or bril- 

 liant, or unusual, or remarkable. In the catalogue which follows, the most extraordinary 

 exhibitions are printed in italics. 



1748. January 12. 



1746. March 1, June 1. 



1747. August 19. 

 1740. October 7* 



1750. February 16, April 3, October 22. 



1752. January 8. 



1757. November 12. 



1758. January 8, March 31. 



1759. September 31. 



1760. May 3. 



1761. November 19. 



1762. May 21, August 10, December 18. 



1763. July 31, September 14, November 11. 



1764. March 5, June 18. 



1765. July 22, August 19. 



1768. July 20, December 5. 



1769. January 5, February 27, June 9, July 2, 



October 7. 



1770. January 18* March 23,t April 19, August 



27. 



1771. March 17, June 2. 



1772. July 8. 



1773. January 17, January 19, July 12, July 17. 



1774. March 13, August 14. 



1777. April 6, September 7, November 3, November 



27.f 



1778. February 17, March 24, April 23, September 



24. 



1779. February 10. 



1786. February 28, March 13, March 19, October 



17. 



1787. June 8, July 13, July 14, October 13, No- 



vember 3,* November 24.* 



1788. July 30* 



1789. March 14, May 23, August 18, November 14. 



1818. March 24. 



1827. August 28, September 8. 



1830. December 11. 



1838. February 21, November 12. 



1839. January 14, January 19. 



1840. August 28. 

 1848. April 6. 



The examination of this list of unusual auroras betrays a very partial chronolo 



During the larger part of the 18th century, down to 1789, they 



distributio 



frequent, there being in all 76 examples, of which 30 are marked as particularly con- 

 spicuous. Between the years 1789 and 1826, a solitary instance is found, on March 

 24, 1818. 



From 1827 to 1848, 1 depend on Dr. Hale's record, which is evidently 



plete in this specialty than the others. But I find even the 



8 



nusual 



mentioned, of which 5 



worthy of italics. For more ample information 



ard 



remarkable displays of auroras since 1827, the catalogue of New York 

 sady quoted, may be consulted to advantage 



Professor Olmsted has selected 

 from the catalogues of Dalton and the Regents' of the State of New York 12 auroras 

 between 1827 and 1848 inclusive, which he assigns to the first rank of auroras, as he 

 has classified them.J I annex a list of those which Dr. Hourii has characterized as 



Red 



t Very extraordinary 



+ Smithsonian 



