ON TERRESTRIAL MAGNETISM AND ATMOSPHERIC ELECTRICITY. 759 



2. On the Magnetic Effects of Electric Railways at Berlin. 

 By Dr. Eschenhagen, of Potsdam. 



Dr. Eschenhagen gave an account of the experiments which had heen made in 

 Berlin to determine the effects of the electric railways there, and the way in 

 which they decreased with distance from the line. Although up to the present 

 the results do not justify any general statement being made, Dr. Eschenhagen 

 anticipates important results from the method he has now adopted of using large 

 coils in series with delicate galvanometers as detectors of earth currents. 



Papers on the subject were also contributed by Dr. C. Schott, Pro- 

 fessor A. W. Riicker, Mr. W. H. Preece, F.R.S., Signor Luigi Palazzo, 

 and Professor J. A. Fleming, F.R.S. 



After the discussion the Permanent Committee passed the following reso- 

 lution : — 



' The Committee are of opinion that any sensible magnetic disturbance produced 

 in a magnetic observatory by electric railways or tramways is seriously detrimental 

 and may be fatal to the utility of the Observatory. They consider that special 

 precautions should be taken to prevent such disturbances, and append as_ an 

 example the provisions for the protection of the Kew Observatory inserted in a 

 Bill passed by the English Parliament authorising the construction of an electric 

 railway, the nearest point of which is to be at a distance of 1 kilometre from the 

 Observatory.' 



Clause for the Protection of Kew Observatory. 



(1) The whole circuit used for the carrying of the current to and from the 

 carriages in use on the railway shall consist of conductors which are insulated 

 along the whole of their length to the satisfaction in all respects of the Com- 

 missioners of Her Majesty's Works and Public Buildings (in this section called 

 * the Commissioners '), and the said insulated conductors which convey the current 

 to or from any of such carriages shall not at any place be separated from each 

 other by a distance exceeding one-hundredth part of the distance of either of 

 the conductors at that place from Kew Observatory. 



(2) If in the opinion of the Commissioners there are at any time reasonable 

 grounds for assuming that by reason of the insulation or conductivity having 

 ceased to be satisfactory a sensible magnetic field has been produced at the 

 Observatory, the Commissioners shall have the right of testing the insulation and 

 conductivity upon giving notice to the Company, who shall afford all necessary 

 facilities to the engineer or officer of the Commissioners or other person appointed 

 by them for the purpose, and the Company shall forthwith take all such steps^ as 

 shall in the opinion of the Commissioners be required for preventing the production 

 of such field. 



(3) The Company shall furnish to the Commissioners all necessary particulars 

 of the method of insulation proposed to be adopted and of the distances between 

 the conductors which carry the current to and from the carriages. 



The following Papers were read : — - 



1. On the Form of the Isomagnetic Lines in the N eighhoiirhood q/] 

 the Volcano Etna.^ By Luigi Palazzo. 



The author made absolute determination of the magnetic elements at a nurnber 

 of stations in Sicily and the neighbouring small island, and relative determinations 

 in the district surrounding each station by means of small portable instruments. 

 In three of the islands, the rocks of which were of volcanic origin, the variations 

 of the elements were found to be large and irregular, even where the constitution of 



' For full details see the Rendiconti d. Accad. d. Lincel, December 5, 1897. 



