472 TRANS. ST. LOUIS ACAD. SCIENCE. 



For all observations where the deflection series were not made the 

 oscillation series was reduced to the temperature of 90°. 7, and the 

 formula on the preceding page was used in determining the mag- 

 netic moment for the day. 



In order to determine the rate of the watch, Jiirgensen 10890, it 

 was compared on eight different days with Dent No. — , and the loss 

 per second was determined as follows : 



second per second, 

 was used in reducing 

 the work of the sum- 



•00028 

 35 

 39 

 36 

 40 

 39 

 42 



3J 



•00037 



The horizontal intensity in the present report and in all former 

 reports is as yet uncorrected for the influence of the magnetic brass- 

 work of the magnetometer. The formula for correcting the values 

 of 1879, 1880, and 1881, is given in the report for 1879,* and is 



H= i,i— 0.0070) H'\, 

 where H" is the observed and ZTthe corrected value. 



Declination. 

 The declination determinations were all made with magnet No. i, 

 in declinometer No. 3. The observed values of declination have 

 received a correction of 2', for the effect of the magnetic brasswork 

 of the instrument as determined in i88o.t The determinations are 

 given in the following tables, which explain themselves. 



Meridian Determinations at Decaturville^ July 29, 1881 4 



The altitude and azimuth circle readings are the means of seven observations. 



A.M. P.M. 



Altitude (lower limb) 52° 32^5 42° S^'-s 



App. Zenith distance 37 27.5 47 27.5 



Sun's radius I5 •« ^5 -8 



Refraction + o .- + i -o 



True Zenith distance 37 12.4 47 12 



* Trans, vol. iv. No. i, p. 134. t Trans, vol. iv. No. «, p. 340. 



I See description of this station on p. 456 of this report. 



