581 



by Mr. "Robert Hunt are referred to. These differences indicate the 

 influence of local conditions, as the differences previously mentioned 

 point at the interference of meteorological variations. 



In order to satisfy himself that he was dealing with currents 

 collected bond fide from the earth, and in no way from the atmo- 

 sphere, arrangements were made with the clerks at Ashford to 

 detach the observing wire from the earth there when required. A 

 considerable number of observations were made during October, 

 November, and December, the results of which are tabulated. 

 Whether the current, as shown by the galvanometer, was weak or 

 strong, it in every instance entirely ceased when" the wire at Ashford 

 was detached from the earth and held insulated ; so that no portion 

 of the result was derived from any other source than the earth. 

 These observations were made at all periods of the day and night, 

 and in all weathers. 



Powerful artificial currents were repeatedly made to flow into the 

 earth by the earth- plates, in order to see whether any effects of 

 polarization were produced ; but the value of the earth-current, as 

 observed before any such experiment, remained unchanged. 



That the currents collected are in no way due to the electromotive 

 power of the earth-plates themselves, is shown by the absence of any 

 sign of a tendency for one or other direction. They are indepen- 

 dent in character and in value of all such influences. To prevent 

 misconception, a list of the earth-connexions used at the several 

 stations that enter into the present investigation is given. 



The author considers it may be premature to regard the subject 

 as tolerably exhausted, as far as the means at his command are con- 

 cerned ; but at this moment he does not notice any other salient point 

 within his reach. When the proposed special wires are ready for 

 Mr. Airy, and consecutive observations are made and compared with 

 the march of the magnetometers, the subject will be within the reach 

 of the able hands of Mr. Airy ; and we may be well assured that the 

 various questions connected with it will be ably discussed by him. 



The results comprehended in this and the previous communica- 

 tion are briefly summed up as follows : 



1st. That currents of electricity are at all times moving in definite 

 directions in the earth. 



2nd. That their direction is not determined by local causes. 



