300 PHENOMENA MANIFESTED IN TELEGRAPHIC LINES, ETC. 



by General IMasi and entered in his minutes on the exhibition of the 

 aurora on the 24th of October, 1870, and was also observed by Messrs. 

 Sureau and H. Tarry along the French lines. * 



The changes, of direction as well as the changes of intensity which 

 the currents that ran over the telegraphic wires underwent, were very 

 great during the aurora. The i)erturbations produced by the aurora 

 began to be noticed on the Italian lines at 4 o'clock 30 minutes p. m. of 

 the 4th. The maximum of the ciriTent manifested itself at G o'clock 31 

 minutes, and in that moment the current changed its direction suddenly. 

 Another maximum somewhat less than the preceding manifested itself at 

 6 hours 37 minutes. At 6 hours 52 minutes the needles of the galvanome- 

 ters remained stationary for about 3 minutes. Toward 8 p. m. the pertur- 

 bations lost much of their intensity, and after this no perturbations took 

 place intense enough to obstruct the transmission of dispatches. Not- 

 withstanding this, the luminous phenomena, taken as a whole, though 

 very variable, were not less splendid from 8 to 10 than they had been 

 from 6 to 8. Mr. Masi in his account of the phenomena states as fol- 

 lows: " Looking at my compass, and at the same time at the luminous 

 phenomena, I observed that the deflection of the compass increased 

 with the increase of the luminosity at the northwest and decreased with 

 its decrease." Mr. Masi's remark of the correspondence between the 

 deflection of the needle of the compass and the luminous variations of 

 the aurora in the northwest may be true, but it seems to me, from the 

 examination I have been able to make of the various observations, that 

 the intensity of the luminous phenomena, considered as a whole, was 

 not proportionate to the amount of the perturbations. Indeed, 1 think 

 that the magnetic perturbations on the telegraphic lines preceded in 

 time the luminous phenomena. 



Mr. Masi was led by his observations to think that, on the telegraphic 

 lines which were situatexl much above the level of the sea, the phenom- 

 ena produced by the aurora were manifested sooner and with greater 

 energy than on lines less elevated. And also that on the latter lines 

 the phenomena exhibited themselves later and with less intensity. Mr. 

 Masi, however, adds that we have not a suflicient number of observa- 

 tions to consider this as an established fact, but that it deserves atten- 

 tion in the future. 



The time given above is mean time at Eome, and it would be very im- 

 portant to ascertain whether in other lines, differing considerably in 

 longitude from the Italian lines, the same phenomena manifested them- 

 selves, and exactly at what time. Mr. H. Tarry, who attempted to 

 ascertain this circumstance, says that the magnetic perturbations which 

 took place on the telegraphic lines manifested themselves at the same 

 time in Italy, France, and America, within perhaps one minute's diiier- 

 ence.t 



* Comptes-reiulns cle I'Acadi^mie des sciences, Vol. LXXIV, page 484. 

 + Comptes-rendus, Vol. LXXIV, page 519. 



