262 C. p. GAUSS ON A NEW INSTRUMENT FOR OBSERVING 



magnetic action of machine electricity were experimentally con- 

 firmed several years ago with the apparatus here ; it appeared, 

 however, worth while to repeat these experiments with the aid 

 of the new and much more sensitive apparatus. Instead of dis- , 

 charging a Leyden jar, or a battery of jars, by a wire chain (as 

 CoUadon and Faraday did), only the conductor and the rubber of 

 an electric machine in the Physical Cabinet were connected with 

 the wire chain passing to the Astronomical Observatorj', which 

 was 13,000 feet in length, including the multipher. The elec- 

 trical machine was then turned with uniform velocity; when 

 this was done with a velocity of one revolution to a second, the 

 five-and-twenty-pound magnet bar in the new apparatus in the 

 Astronomical Observatory was thereby kept at a deflection cor- 

 responding to 144 parts of the scale (somewhat more than 50 

 minutes), — the deflection being positive or negative according to 

 the direction in which the current passed through the multiplier. 

 The experiments showed as much regularity as could be wished. 

 But the circumstance especially remarkable is that the electro- 

 magnetic effect remained the same even when the length of the 

 chain was increased to above a German mile by the introduction of 

 other apparatus. This might seem to be an essential difference 

 from other currents, excited either hydro-galvanically, thermo- 

 galvanically, or by induction ; the intensity of which, indicated 

 by the magnitude of the electro-magnetic effects, becomes con- 

 stantly smaller the longer the conducting apparatus ; but I find 

 in it a striking confirmation of the theory, according to which 

 the unequal intensity, indicated by the unequal electro-mag- 

 netic action of two galvanic currents, is nothing more than 

 the unequal quantity of electricity passing through each sec- 

 tion of the conducting apparatus in a fixed time. With other 

 modes of excitation, a given electromotive force developes less 

 electricity in a given time, the greater the opposition made to 

 the current by the longer chain ; in our experiment, on the 

 contrary, the quantity of electricity in motion depends merely 

 on the play of the machine, and all electricity passing to the 

 conductor in the form of sparks must traverse the whole chain, 

 be it long or short, in order to equalize itself with the opposite 

 electricity from the rubber. 



In order to demonstrate the preference due to the new 

 apparatus over the magnetometer in electro-magnetic tele- 

 graphy, we must first consider somewhat more closely the 



