172 



At intervals from 1837 to 1853, observations of intensity 

 were made both with Lloyd's Needle, and Christie's Needle, 

 mostly at the same times and places as those already mentioned 

 while treating of the dip. At each observation, the temperature 

 was recorded, and to the result a suitable correction was 

 applied. The needles during this long period have lost in 

 magnetic force — at first the loss was rapid, afterwards more 

 slow. In the case of Lloyd's needle, the intensity indicated at 

 York has sunk through the following series (corrected for tem- 

 perature.) 



1837, June 3, 5, 15, (5 obs.) 9647") Loss in 15 months 



1838, Aug. 1, Sept. 7, Oct. 2, (4 obs.) 95723 '0075 

 1838, Feb. 19, 20, Sept. 4, 5, 7, 13, 7 Loss in 9 months 



} 



17, 19 (8 obs.) 95573 '0015 



1846, Aug. 26 9307^ ") 



f (Loss in 120 months 



r 9302 r -0255 



1850, May 16, 24 9297-Oj J 



After this observation, the needle was, by accident, (the only 

 one which has happened to it in 16 years) dropped. The 

 magnetism was then found — 



1850, May 24 ... 9159-7 After which the rate of loss 



has been continued. 



1851, April 29 ... 9126-4-i Loss in 38 months 

 1853, Aug. 2 ... 9095-63 -0064. 



Whence the rate of loss in 1837, was -0005 in a month, 

 in 1837—8, -0001-7 

 in 1838—1848, -0002-1 

 in 1850—1853, -0001-7 



The subjoined Table gives the relative Intensities at several 

 stations in the county, and a few beyond it ; each observation 

 being corrected for temperature, and referred to a general scale 

 by comparison with nearly contemporaneous experiments at 

 York. The geographical centre of this series is almost exactly 

 the same as that of the series of dips. 



