Ma DUNLOP'S Account of Observations made in Scotland, 



OBSERVATIONS AT MAKERSTOUN, continued. 



h. m. B. 



1829, January 20. at 2 43 P. M. 300 vibrations, reduced to HANSTEEN'S standard, Mean 822-16 



1830, January 23. at 2 30 P. M. 300 vibrations, - - 822-12 



1829, June 28. 

 29. 



at 7 6 p. M. 300 vibrations, = 

 at 9 48 A. M. 300 vibrations, 



s. 

 ribrations, = 821-32 ) 



vibrations, = 823-20 I 



Daily variation, 



= 1-88 



Mean 822-14 



Mean 822-26 



Diff. = -12 



FLAT NEEDLE. 



By comparing the results contained in the above table, it appears that the magnetism of the flat 

 needle is not stationary. Indeed, Professor HANSTEEN found it so, and expressed himself to this effect, 

 in a letter to Dr BREWSTER, which accompanied the apparatus, that " he suspected the magnetism in 

 the flat needle had not yet become stationary, and that he had accompanied the apparatus with a needle 

 of his own (Cylinder No. I.), which had been used in several expeditions, and could be more depended 



upon." 



No. I. Cylinder. Flat Needle. 



In Christiania, 1827, June 24, Time of 300 vibrations, = 800- seconds = 980- seconds 

 At Makerstoun, 1829, June 28, Time of 300 vibrations, = 802- = 1024- 



Difference between the places by both needles, = 2' seconds = 44- seconds 



Assuming the magnetism of No. I. to have remained stationary, the flat needle has, in two years, in- 

 creased its time in making 300 \ibrations, no less than 42 seconds of time ; and the following deductions 

 will shew the decrease of its magnetic force to be very unequable, proportionate to the time elapsed : 



Time. Diff. Ann. Increase. 



1827, June 24,. (Reduced to Makerstoun) 300 vib. flat needle, = 982-5 seconds 



= 37-1 =r 26 seconds 



1828, Dec. 1. At Makerstoun, 300 vib. = 1019-6 



1829, June 29. 



1830, Feb. 14. 



300 vib. 

 300 vib. 



= 1024-7 

 = 1039-8 



= 5-1 = 9 

 = 15-1 = 24 



