MAGNETIC SURVEY OF GREAT BRITAIN. 



139 



Tabular view of the variations of the angle 6, for the purpose 

 of ascertaining the loss of force undergone by the needles, 

 and the period of the change. The angles are reduced to 

 the standard temperature, 60°*. 



Table XLIII. 



Note hy Mr. Lloyd. — It appears from this table that Needle 

 L. 3 sustained a loss of force in the interval of time which elapsed 

 between the two observations at Shrewsbury. Now the obser- 

 vations at Dublin in April and May prove that the loss sus- 

 tained by the needle during the series of observations in spring 

 was comparatively trifling ; while, from the results obtained at 

 the same place in May and August, it appears that the mag- 

 netism of the needle remained perfectly steady in the interval 

 between the two series. We are consequently conducted to 

 the conclusion, that the change occurred in the short interval 

 between the observations at Dublin on the 5th of August and 

 those at Shrewsbury on the 9th ; and we have every reason to 

 believe that it was previous to the observation at Birkenhead, 

 and probably due to some accident in the passage across the 

 channel. The magnetism of the needle appears to have been 

 steady during the remainder of the autumn series. This, we 

 think, will appear from the difference of the angles at Shrews- 



• For the mode of effecting this reduction see Fifth Report British Associ- 

 ation, page 147. 



