4-10 The Rev. Dr. Lloyd on Earth-currents, and their 



these two lines were continued for fourteen consecutive days, 

 commencing May 17, 1848. Of these days of observation, how- 

 ever, six are incomplete, viz. May 17, 19, 20, 23, 24, 30; and 

 another day (May 27) appears from the Dublin observations to 

 have been a day of considerable magnetic disturbance. Omit- 

 ting these, as unsuited to furnish true mean results, the means 

 of the remaining days are as follow. The positive numbers indi- 

 cate currents proceeding towards Derby, and the negative cur- 

 rents in the contrary direction. 



Table II. — Mean observed Values of the Intensity of the Cur- 

 rents traversing the Wires uniting Derby and Rugby, and 

 Derby and Birmingham, respectively. 





Derby ar 



d Rugby. 



Derby and Birmingham. 



Hours. 























A.M. 



P.M. 



A.M. 



P.M. 



, 



-1-4 



0-3 



-50 



-51 



02 



1-5 



-91 



-8-5 



2 



25 





-55 





2-9 





-77 





3 



1-6 



17 



-27 



-3-3 



09 



1-3 



-7-4 



-7-4 



4 



1-1 





-2-4 





0-7 





-72 





5 



0-5 



1-2 



-1-8 



-2-3 



06 



1-2 



-3-6 



-51 



6 



27 





-32 





2-8 





-63 





7 



31 



30 



-0 6 



-11 



3-9 



4-1 



-4-5 



-4-7 



8 



31 





-0 2 





5-9 





-3-4 





9 



2-4 



1-8 



0-4 



02 



4-2 



3-4 



-0-8 



-17 



10 



-0-9 





01 





-0-6 





-17 





11 



-43 



-36 



0-4 



0-6 



-7 2 



-5-8 



0-3 



0-4 



12 



-51 





17 





-81 





2-8 





It will be observed that the changes indicated by these num- 

 bers are very systematic. In the wire connecting Derby and 

 Birmingham the current flows southwards from 10 a.m. to 10 

 p.m. inclusive, and northwards during the remaining hours. In 

 the wire connecting Derby and Rugby the southward current 

 lasts from 10 a.m. to 8 p.m. inclusive, and it is northward (with a 

 single exception) during the remaining hours. There arc, how- 

 ever, as might be expected in so short a series, some irregulari- 

 ties in the course of the changes. In order to lessen these, and 

 at the same time to confine the results to such as are comparable 

 with the preceding, I have given (in the alternate columns of the 

 Table) the means corresponding to the alternate hours commen- 

 cing at 1 a.m. computed by the formula 



t(« + 2* + c). 

 The numbers so obtained are projected into curves in the an- 

 nexed diagram, having been previously multiplied by constant 

 coefficients in order to equalize the ranges with those of the com- 

 puted results. The dotted lines in both cases are the corrcspund- 



