Ixviii Introduction to the Makerstoun Observations, 1845 and 1846. 



124, From these we find for 



Professor Bache's bar, named 1 63°-9 to 90°-3 a = 0-000095 f,^ ... -. „ oco-ot. 

 B, marked 4, j 38H to 63°-9 y=0000089 (Variation of yfor 25 Fahr.= 



1 65°-4 to 89°-8 ^=0000096 f 



J 39°-8 to 65°-4 ^=0000084 [ 



14 



Professor Bache's bar, named 1 65°-4 to 89°-8 ^=0000096 

 B— unmarked, J 39°-8 to 65°-4 ^=0000084 



8 



Sir Thomas Brisbane's bar, 1 64"-7 to 89°-6 y = 0-000106 f _q 



named M, unmarked, ] 39°-8 to 64°-7 y = 0-000096 \ 



ProfessorFoRBES'8bar,named\ 64°-8 to 88°-2 ^ = 0-000295 f 

 F, unmarked, J 39°-5 to 64°-8 y= 0000316 t 



Sir Thomas Brisbane's bar, I 67°-8 to 94°-l ^=0000200 / 

 marked I. 23, j 38''-8 to 67°-8 ^=0000184 \ 



10 



14 



__^ 

 13 



125. For these magnets, therefore, the temperature coefficient varies from 1 



o 



to i of its mean value from the mean temperature of 50° to that of 75°, the co- 

 efficient being greater at high temperatures than at low temperatures. A similar 

 result was obtained by Mr Christie long ago,* and lately by Mr Airy and Colonel 

 Sabine. This difference has not been found to exist for the large variation magnets 

 (see Introduction^ p. xliv.). 



126. The following are the results of series of observations for the temperature 

 coefficients of different magnets. 



Table 15. — Results of Observations for the Temperature Coefficients of different 

 Magnets, the Temperature Rising and Falling, made 1843-7. 



Date. 



• 



Description of Magnet. 



Whole 

 Num- 

 ber of 

 Results. 



Tempe 

 FaUing. 



rature 

 Rising. 



Difference 



Rising 



•minus 



Falling. 



<!• 



<l- 



Nov. 9, 1843 

 11, 1843 

 Jan. 27, 1844 

 June 30, 1846 

 May 21, 1847 



May 28, 1847 

 Sept. 8, 1847 



Bifilar Magnet (15-inch) 



17 



9 

 16 

 6 

 7 

 8 

 5 

 6 

 6 

 2 

 6 

 4 

 3 

 2 



0-000290 

 0-000278 

 0-000067 

 0-000280 

 0-000311 

 0-000408 

 0-000747 

 0-000264 

 0-000210 

 0-000323 

 0-000100 

 0-000091 

 0-000089 

 0-000098 



0-000298 

 0-000296 

 0-000079 

 0-000289 

 0-000301 

 0-000395 

 0-000745 

 0-000278 

 0-000212 

 0-000333 

 0-000121 

 0-000091 

 0000092 

 0-000104 



+ 0-000008 

 ■f 0000018 

 + 0-000012 

 + 0-000009 

 -0-000010 

 -0-000013 

 -0000002 

 + 0000014 

 + 0-000002 

 + 0-000010 

 + 0-000021 

 0-000000 

 + 0-000003 

 + 0-000006 





Q./^f^^iTipli A/rncrTipf "rinmPfl "P • 



3-65-incli Magnet, unmarked 



3-incli Magnet, marked S. 43 



3-incli Magnet, marked S. 29 



3-incli Magnet, hollow, marked B. 6. 



^.f\^_-i-nf»li IVTrKynpf Tiflmpfl "P 





3-65 Collimator Magnet, marked 4, named B. 

 3-65 Collimator Magnet, unmarked, named B. — 



^.fi^ OnniTuntnT ATncmpf Tinmpfl AT 







The observations in some instances are too few, and with too large probable 

 errors to be sufficient for the determination of the difference of the coefficient, for 



rature in handling during the removal of the bar, an error would be introduced always of the same 

 sign if the north end has always the same position at the beginning. 

 * Philosophical Transactions, 1825, p. 63. 



