Intelligence and Miscellaneous Articles, 323 



amounts to the same thing, an ascending current of positive elec- 

 tricity, in the conducting wire which joins two places at different 

 heights above the sea-level. 



This furnishes the explanation of a phenomenon frequently ob- 

 served, and under conditions quite free from objection, by M. Mat- 

 teucci. He observed that in every mixed circuit, consisting of a 

 layer of earth and a metal wire the ends of which are sunk in the 

 ground, minute precautions being taken to avoid any thermal or chemi- 

 cal action, the wire is traversed by an electrical current whose direction 

 is constant whenever the soils in which the ends are plunged are of 

 unequal heights. The current ascends on the metal wire ; its intensity 

 increases with the length of the wire, and with the difference in 

 level of the ends. M. Matteucci has convinced himself that at the 

 higher station there were very intense indications of positive elec- 

 tricity, while these signs were feeble, or were entirely wanting, at 

 the lower station. 



All this, then, agrees with the theoiy which I have laid down ; 

 but to confirm the exactitude of the considerations on which it is 

 based, I have tried to reproduce the phenomenon observed by M. 

 Matteucci by means of a laboratory experiment. With this view I 

 placed on an insulating support a sphere of about 30 centimetres 

 diameter, made of porous earthenware, or of wood covered with 

 bibulous paper, so as to have, by wetting the surface, a moist con- 

 ductor representing the earth. I fixed to the highest part of the 

 sphere, in contact with its moist surface, a small metal disk ; a second 

 one was arranged in the same manner at a distance of from 50 to 90 

 degrees from the first. I then joined the two disks by the wire of a gal- 

 vanometer ; no current showed itself, either positively or negatively, 

 even when the insulated sphere was positively or negatively electrified. 

 By means of an insulated rod I then suspended, at a distance of 

 2 to 3 centimetres above the sphere, a plate slightly concave on the 

 lower side, and of such dimensions that it only covered a small por- 

 tion of the sphere — that, namely, in the midst of which was the 

 upper metal disk, and therefore not the 'portion in which the other 

 disk was placed. The apparatus being thus arranged, I charged 

 the sphere representing the earth with negative electricity from 

 a machine, the positive electricity of which was led to the concave me- 

 tallic surface representing the atmosphere. The galvanometer quickly 

 indicated the existence of a current, the direction of which was from 

 the lower to the upper disk ; this current was perfectly regular, and 

 lasted as long as the machine was at work. It is to be observed 

 that the upper disk was in that part of the sphere where most nega- 

 tive electricity was accumulated, under the influence of the insulated 

 positive plate, while the second disk was in the part withdrawn from 

 this influence — that, therefore, in which the quantity of negative 

 electricity was small and flowed out, in proportion as it was pro- 

 duced, into the surrounding air. The current proceeded, therefore, 

 in the wire which joined the two unequally electrified portions of 

 the negative sphere from the least- electrified portion to that which 

 was more so, exactly as is the case in the natural phenomenon ob- 



