THENOMENA MANIFESTED IN TELEGRAPHIC LINES, ETC. 301 



Bat the facts on wMcb he bases his coDclusion seem to me too gen- 

 eral and too few, and that we require more particular and more numer- 

 ous observations before accepting his statement as that of an estab- 

 lished fact. Mr. Tarry also adds that " in the telegraphic line from 

 Brest to Paris, from oh. 55m. to G o'clock p. m. (Paris time) there were 

 two very singular waves. The deflection of the needle at first increased 

 progressively from 0° to + G0°. Then there was for one minute a firm 

 adherence of the armature of the telegraphic instrument, with per- 

 sistent deflection. After this the needle went gradually down to 0, 

 then up to + (30°, where it remained one minute. At six it jumped 

 suddenly from + 60° to - 00°.* 



I have tried to ascertain whether in the interval of time which cor- 

 responds to between 5h. 55m. and 6 o'clock, mean time of Paris, there 

 were any observations made in Italy, in order to compare them with 

 those made in France, and I find that from the observations made at 

 Eome by Messrs. Perelli and Gotti, on the line from Rome to Milan, and 

 from those made at Florence by Messrs. Donalisio, Guidi, and Gabrielli, 

 on the line from Florence to Turin, the following table can be con- 

 structed : 



Line from Borne to Milan.] 



Mean time of Paris. The needle of*the galvanometer, at 1000 turns. 



From 5^ 55"" to 5^ 57™, moves gradually from — 62° to -f 78° 



5 57 5 57.5, passes rapidly from -f 78 — 50 



5 57.5 5 58, " " "... * - 50 +73 



5 58 5 58.5, " " " 4-73 - 65 



5 58.5 5 59 almost stationary between -f 73 — 65 



5 59 6 00.5, rushes over zero to +60 



•I 



Line from Florence to Turin. 



From 5^^ 55™ to 5'^ 56™, oscilates and goes rapidly from — 80° to + 80° 



5 57 moves rapidly from +80 — 60 



5 58 " " " — 60 +75 



5 58.5 moves from +75 — 05 



To 6 00 almost stationary towards — 70 



then jumps violently to +10 



In comparing the preceding observations with those reported by Mr. 

 Tarry, it seems as if we may conclude that both in Italy and in France 



^Comptes-rendus, Vol.LXXIV, page 484. 



tTlie line from Rome to Milan passes tlirough Foligno, Florence, Bologna, and Pia- 

 cenza. The line from Florence to Turin passes through Empoli, Pisa, Spezia, Genoa. 

 The time of the Italian observations are reduced to mean Paris time, by subtracting 

 40'". from the time indicated by the observers of Rome and Florence. The observa- 

 tions made at Rome are preceded by the following notice. It being known on which 

 side the needle is deflected when Rome sends a iiositive current, the deflection ob- 

 served on the opposite quarter is maiked thus, (+) and that on the same quarter is 

 marked thus ( — .) The resistance of the galvanometer used in Florence was 101, and 

 that used at Rome 104 Tiemens units. 



