Inteoduction. 



XXXIX 



divisions, are given, with the periods to whicli they apply, in the following table, 

 and at the foot of each page of the Daily Observations. 



The adopted value of 

 See section 7. 



= 71° 12'. 



Table 18. — ^Values of k and q for the Balance Magnetometer, and the periods to which 



they apply. 



Periods to which the Quantities 







apply. 





Value of k. 



Value of q. 



1841. 







Mic. Div. 



d. h. 



d. h. 







July 11 20— July 



23 5 



0-0000127 



5-74 



Aug. 4 20 — Aug. 



28 5 



0-0000143 



5-10 



Sept. 5 20— Sept. 



30 5 



0-0000127 



5-74 



Oct. 6 20— Nov. 



30 5 



00000118 



6-20 



1842. 









Jan. 12 20 — Jan. 



22 5 



0-0000127 



5-74 



Jan. 23 20— March 21 5 



0-0000140 



5-20 



March 21 20 — April 



16 5 



0-0000118 



6-20 



April 17 20— Oct. 



8 5 



0-0000130 



5-60 



Oct. 9 20— Dec. 



31 5 



0-0000143 



5-10 



§ 6. ObSEEVATIONS foe the TeMPEEATUEE CoEEECTIONS of the BiFILAE AND 



Balance Magnets. 



46. June 16. 1841. — ^Experiments were made to determine the effect of tempera- 

 ture on the bifilar and balance magnets. For this purpose, the magnet was placed 

 in a copper trough, and surrounded with ice, or water of the desired temperature. 

 The trough was placed on a stand upwards of 5 feet east of the declination instru- 

 ment, so that the axis of the magnet should be at right angles to that of the decli- 

 nometer. A thermometer was placed in the trough beside the magnet. Seven 

 readings of the declinometer were made in each of the following positions, N. pole E., 

 N. pole W., N. pole E., in order to eliminate the changes of declination. The ob- 

 servations are not worth recording, owing to the imperfections of the method ; the 

 following is the final result for the bifilar magnetometer, q = 0*000353. 



January \^ 2, &c., 1842. Experiments were made on the balance magnet. The 

 same method was adopted as on June 16, excepting that the balance needle was placed 

 nearer the suspended magnet (within 4 feet) ; that the needle was repeatedly re- 

 versed, and the bifilar magnetometer observed during the experiments. 



The discordances of partial results were so great, that only the final result is 



given here, 



q = 0-0001283. 



