Temperature Coefficient of the Balance Magnet. li 



<j = 7 - 90 micrometer divisions. 



80. Since this value was obtained, several other determinations have been made, 

 by comparisons of observations in 1844, 1845, and 1846 ; all the results obtained are 

 o-iven in the Table below ; several of the results obtained more lately have been de- 

 duced from periods ill fitted to give a good value ; the whole, however, have been 

 given in order to shew the amount of error that may be expected in using bad series. 

 In one or two of these cases the amount of disturbance has not been very consider- 

 able, but the greatest variations of the daily mean vertical force have happened to 

 occur at the same time with the greatest variations of mean temperature ; it is 

 believed that it is to this cause chiefly that the differences of the results are to be 

 attributed. 



Table 9. — Determinations of the Temperature Coefficient of the Balance Magnet. 





Sum of 







Sum of 





Period. 



Diff. 



Value of 



Period. 



Diff. 



Value of 





Temp. 



?'• 





Temp. 



?'• 



1843. 



o 



Mic. Div. 



1844. 



= 



Mic. Div. 



Jan. 16 — Jan. 21 



58-4 



8-21 



Nov. 4 — Nov. 30 



1066-2 



6-92 



Jan. 23 — Jan. 28 



90-9 



6-99 



Dec. 2— Dec. 28 



939-0 



7-20 



Jan. 30— Feb. 4 



640 



7-21 



1845. 







Feb. 6— Feb. 11 



67-8 



6-69 



Jan. 6— Feb. 8 



2086-3 



7-57 



June 1 — June 30 



1885-8 



7-82 



Feb. 26— Mar. 28 



1830-1 



8-00 



Sept. 6— Sept. 16 



120-4 



8-04 



Apr. 10 — May 10 



1279-1 



9-08 



1844. 







June 2 — June 30 



1551-6 



8-47 



Jan. 1 — Jan. 26 



971-4 



9-27 



July 7 — Aug. 6 



1069-8 



1001 



Feb. 5— Mar. 6 



1392-5 



9-30 



Sept. 9— Oct. 13 



1580-6 



7-81 



May 9— May 24 



350-6 



7-93 



Dec. 11— Jan. 10 



1585-2 



1017 



May 29— June 29 



1693-1 



7-43 



1846. 







July 4 — Aug. 3 



1360-9 



7-74 



Nov. 30— Dec. 26 



1190-2 



7-72 



Aug. 4— Sept. 6 



904-0 



7-90 









Giving the differences for all the series equal values, and dividing the sums of 

 differences of the daily means in micrometer divisions by the sums of differences of 

 the daily mean temperatures of the needle, we have 



q' = 8 - 23 mic. div. ; 



but if the results from the bad series for July 7 — August 6, 1845, and December 

 10, 1845 — January 10, 1846, be rejected, the value would be 



q' = 7-99 mic. div. 



If the whole series were properly weighted, it is believed that the resulting value 

 of q would be less than 8-00 mic. div. The excellent series, November 30 — De- 

 cember 26, 1846 (after an adjustment July 1846) gives 



