316 CARNEGIE INSTITUTION OF WASHINGTON. 



Note on a possible explanation of the "electric tide" observed at Jersey. S. J. Mauchly. 

 Terr. Mag., vol. 24, No. 2 (June 1919). Washington. 



Since 1916 M. Dechevrens^ has obtained at Jersey, England, continuous 

 records of the electromotive force indicated by a galvanometer one terminal 

 of which is joined to the pipes of the city gas-system and the other to the pipes 

 of the private water-system of the St. Louis Observatory, whose site is on a 

 hill of considerable elevation above the city. 



The diurnal-variation curves unmistakably indicate a connection between 

 the observed electromotive force and the tides of the local harbor. Dechev- 

 rens has tentatively suggested that the electromotive force may be induced 

 by the tidal waters cutting across the Earth's magnetic field. 



Recent observations at Kew by E, G. Bilham,^ showing a close connection 

 between the water-level in an experimental well and the tides in the nearby 

 Thames suggest the following as a possible explanation of the effects observed 

 at Jersey : 



If the normal tides in the Jersey harbor are assumed to cause periodic 

 variations in the height of the local water-table similar to those observed at 

 Kew, then, from the theory of concentration cells, a periodic variation would 

 be a necessary characteristic of the electromotive force between the two pipe 

 systems, provided one system in more accessible to the periodic infiltration 

 of tidal water than the other. Likewise, the successive exposure of differently 

 composed or unequally corroded parts of the lower system might give rise to 

 periodic variations in the electromotive force. 



Judgment as to whether the variations of electromotive force resulting from 

 these causes should be considered as accounting for nearly all or for very little 

 of the observed effect must be based upon topographic and geologic details 

 and certain supplementary experiments. If water-table data similar to those 

 obtained at Kew were available for the lower part of the area covered by the 

 gas-pipe system, they would go far toward indicating whether the observed 

 effects should be attributed chiefly to electromagnetic induction or to elec- 

 trolytic action. 



iSee Terr. Mag., vol. 23, pp. 37-39, 1918; Terr. Mag., vol.' 23, pp. 145-147, 1918; Comptes 

 Rendus, vol. 167, pp. 552-555, 1918; Terr. Mag., vol. 24. pp. 33-38, 1919. 



2 See Proc. Roy. Soc, vol. 94, pp. 165-181, 1918; Proc. Roy. Soc, vol. 94, pp. 476-478, 1918; 

 Q. J. R. Meteor Soc, vol. 44, pp. 171-189, 1918. 



