DEGLI SPETTROSCOPISTI ITALIANI 67 



the observed retardation of Encke's comet, is siich that it wouid supposi a co- 



220 285 



lumn of mercary somewhere between -—-^ and —jò of au inch high. 



6. There is some probability that the electric cnrrents which give rise to au- 

 ras are propagated in a medium which pervades ali space, and that the spectrum 

 of the aurora is, in realily, the spectrum of that medium. 



7. It is not improbable that the tails of ali large comets will be found to give 

 spectra siniilar to that of the aurora, although additional lines may be preseut. 



Macchie solari osservate all'Equatoriale di Merz di Palermo 

 nei mesi di gennaro, febbraro, marzo ed aprile 1874 



da F. Tacchini. 





fa 





H B 



-<» 







fS 





m là 





M NN 



1874 



s 



o 



53 



5 ^ 

 g < 



a 2 



— EH 



2 



à g 

 4 



1874 





o 

 b 



9 



3 5 





2 



Genu. 10 



4 





Marzo 21 



2 





11 



7 



34 







2 



22 



3 



28 







3 



22 



6 



15 







6 



24 



2 



4 







4 



23 



5 



35 







6 



27 



6 



11 







4 



Febbr. 8 



3 



29 







7 



28 



4 



24 







8 



10 



3 



17 







5 



29 



3 



9 



1 





3 



13 



6 



12 







5 



31 



5 



11 







5 



16 



4 



7? 







3 



Aprile 1 



4 



17 







4 



19 



5 



19 



2 





5 



2 



4 



18 







4 



22 



3 



32 



2 





6 



4 



4 



30 







5 



24 



8 



11 



3 





7 



5 



4 



18 







4 



25 



9 



25 



1 





7 



7 



5 



15 







5 



26 



6 



18 



2 





7 



10 



8 



8 







4 



27 



9 



22 



2 





8 



14 



4 



11 







5 



Marzo 4 



8 



39 







4 



17 



1 



19 







3 



5 



8 



41 







4 



18 



2 



16 







2 



7 



6 



15 











19 



1 



19 







2 



8 



5 



12 







5 



20 



1 



13 







2 



9 



5 



17 







3 



21 



1 



5 







2 



15 



4 



47 







3 



22 







3 







1 



17 



3 



23 







3 



23 







3 







2 



18 



3 



26 







5 



24 







3 







2 



19 



2 



14 







3 



25 







1 







1 



20 



2 



5 







2 



26 



1 



5 







3 















27 



1 











1 



