120 Magnetogy-aph- traces at Kew and Lisbon. [Jan. 28, 



the Lisbon horizontal-force curve, in which we may suppose two indepen- 

 dent forces to be represented, is probably on the whole the most hke the 

 corresponding Kew curve. Corresponding points occur at the same abso- 

 lute time for both stations. 



The disturbance-waves for the horizontal force and declination are 

 greater at Kew than at Lisbon. 



The Kew peaks and hollows are simultaneously produced at Lisbon in all 

 the elements, but to a smaller extent than at Kew ; also the direction is 

 reversed in the case of the vertical force, so that a sudden small increase of 

 vertical force at Kew corresponds to a diminution of the same at Lisbon. 



The writers of this paper are well aware that before the various points 

 alluded to in their communication can be considered as established, a more 

 extensive comparison of curves must be made. But as the subject is new 

 and of great interest, they have ventured thus early to make a preliminary 

 communication to the Royal Society. They will afterwards do all in their 

 power to confirm their statements, which in the meantime they submit to 

 this Society as still requiring that proof which only a more prolonged in- 

 vestigation can afford. 



Note regarding the Plates. 



Increasing ordinates denote increasing westerly declination, and also in- 

 creasing horizontal and vertical force. 



The following are the scale coefficients applicable to the different 

 diagrams : — 



Horizontal force, Kew. One inch represents 0*041 English unit. 



Ditto Lisbon. „ „ 0-035 „ for July 15 



Ditto do. „ „ 066 „ for July 17. 



Ditto do. „ „ 0-041 „ for the other 



curves. 



Declination do. „ 0*040 ,, 



Vertical force do. „ „ 0*026 



APR, 19, ML 



