80 



ON THE PERIODICITY OF THE AURORA BOREALIS. 



Spydberg. Wilse. Berne. Studer. 



Cambridge. Wigglesworth. Lovering. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



St. Petersburg. Euler. Spydberg. Wilse. 



Stockholm. Nicander. 



Cambridge. Wigglesworth. Lovering. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



Stockholm. Nicander. Sagan. Preus. 



»Sf. Petersburg. Euler. 



Stockholm. Nicander. 



St. Petersburg. Euler. 



Cambridge. Williams. 



Salon. Holyoke. Lovering. 



St. Petersburg. Euler. 



Stockholm. Nicander. 



Berlin. Beguelin. Sagan? Preus. 



Copenhagen. Bugge. 



Brussels. Mann. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



Stockholm. Nicander. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



New Haven. Stiles. Loomis. 



Stockholm. Nicander. 



St. Petersburg. Euler. 



Stockholm. Nicander. 



<Sif. Petersburg. Euler. Jena. Zeissing. 

 Berlin. Beguelin. Delphi. Van Swinden. 

 Eatisbon. Heinrich. Sagan. Preus. 



Brussels. Mann. Stockholm. Nicander. 



Erfurt. Planer. Padua. Toaldo. 



Coperihagen. Bugge. 



Sagan ? Preus. 



Mannheim. Hemmer. Sagan ? Preus. 



Sagan. Preus. Brussels. Mann. 



Stockholm. Nicander. 



St. Petersburg. Euler. Sagan. Preus. 



St. Petersburg. Euler. Copenhagen. Bugge. 



Sagan. Preus. Eatisbon. Heinrich. 



Stockholm. Nicander. Mannheim. Hemmer. 



Berlin. Beguelin. Wiirzburg. Egel. 



Spydberg. Wilse. 



Stockholm. Nicander. Brussels. Mann. 



Mannheim. Hemmer. Sagan ? Preus. 



Berlin. Beguelin. Sagan. Preus. 



Stockholm. Nicander. 



Berlin. Beguelin. Sagan ? Preus. 



Apr. 26. 



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Cambridge. Wigglesworth. Lovering. 



Cambridge. Williams. 



New Haven. Stiles. Loomis. 



Stockholm. Nicander. 



St. Petersburg. Euler. Berlin. Beguelin. 



Prague. Strnad. Sagan ? Preus. 



Cambridge. Williams. Sagan ? Preus. 



St. Petersburg. Euler. 



Stockholm. Nicander. 



Cambridge. Wigglesworth. Lovering. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



Cambridge. Wigglesworth. Lovering. 



Cambridge. Williams. 



Salem. Holyoke. Lovering. 



Delphi. Van Swinden. Sagan. Preus. 



Brussels. Mann. Prague. Strnad. 



Stockholm. Nicander. Eatisbon. Heinrich. 



Stockholm. Nicander. Delphi. Van Swinden. 



New Haven. Stiles. Loomis. 



Berlin. Beguelin. Kendal. Dalton. 2 



Paris. Cassini. Brussels. Mann. 



Copenhagen. Bugge. Delphi. Van Swinden. 



St. Petersburg. Euler. 



Stockholm. Nicander. 



Berlin. Beguelin. Brussels. Mann. 



Berlin. Beguelin. Brussels. Mann. 



Berlin. Beguelin. 



Brusselt. Mann. 



Berlin. Beguelin. 



Kendal. 



Brussels. 



Berlin. 



Berlin. 



Prague. 



Brussels. 



Brussels. 



Berlin. 



Dalton. 



Mann. 

 Beguelin. 

 Beguelin. 



Strnad. 



Mann. 



Mann. 

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Berlin. Beguelin. 



Paris. Cassini. 



Brussels. Mann. 



Brussels. 

 Loomis. 



Mann. 



New Haven. Stiles. 

 Brussels. Mann. 

 Brussels. Mann. 

 New Haven. Stiles. Loomis. 

 Berlin. Beguelin. Kendal. Dalton. 

 Borne. Calandrelli. Brussels. Mann. 

 Salem. Holyoke. Lovering. 

 Berlin. Beguelin. Padua. Toaldo. 

 Sagan. Preus. 



Cambridge. 



Wigglesworth. 



Lovering. 



1 Meter. Obserr. and Essays, p. 54. 



