Oa SS 
ON COMPARISON OF MAGNETIC INSTRUMENTS 89 
Comparison of Magnetometer No. 70 with the Kew Standard Instrument. 
Declination. Observer : Professor Ricker. 
Date Time ir ie Declination O Bane S'-C=Z E re 
H. M. ° Ul / U , ee 
July 6* |12295| K 17 251 | 544 | (307) | — is 
fee i210} K 21:3 | 500 | 313 pet 
3 16 13 12 S 21°3 49:2 — 32:1 —0'8 
op ol KD 14 45 K 20°3 50°1 30°2 — — 
a LG 15 2 S 20°7 49°5 -— 31-2 —10 
my LG 15 54 K 18°5 48:0 30°5 | _ 
cy all 16 36 S 19-0 47-5 —_ 31:5 —1:0 
yy es 16 20 K 18°4 47-0 (31:4) —_ 
ely 11 42 K 22°2 515 30°7 — = 
20 13 9 S 22°8 51:7 — 311 —0-4 
Pe 1091-49 |. K 21-1 51:0 | 301 a a 
ose.) 19 565. |:58 240 | 52:3 eae 31-7 —16 
ee | 144} gs 23-4 | 52-0 ve 30-4 
ee 15 2 K 218 51:0 30°8 — +04 
pea) | 1230|.. K 250 | 531 | (319) | — = 
Mean 5 — — — — 30°6 313 —07 
Comparison of Magnetometer No. 70 with the Kew Standard Instrument. 
Declination. Observers: Professor Ritcker and Mr. Watson. 
Date Time ole Declination oe. valle S'-C=Z i see 
H. M. (e} Li ' fi f ! 
Oct. 5* 12 32 K 17 201 50:2 (29:9) _— — 
oases |i¢ 9| °K 139 | 470 | (319) | — pe 
ay ee Tae 5 K 21:9 50°9 31:0 
Hs 9 11 40 S 21°8 51:0 — 30:8 +02 
nee LO 10 41 K 156 43:7 319 
we 0 Il 27 S 18:2 46:7 — 315 +04 
“4, Maat 15 44 K 18:3 48-1 30°2 — 
ee LL 16 0 5 18°6 48-0 — 30°6 —O-+4 
a 2 10 54 8 18°6 3 17°3 
we 2 12 43 K 21:7 5:2 16°5 —_ —0°8 
i 2be 12 29 K 18°7 49°0 (29:7) — — 
Mean — — — — — — -—O1 
In the case of the horizontal force the two necessary observations— 
the vibration and the deflection—are indicated by the letters V and D. 
If H’ be the value of the horizontal force deduced from these observa- 
tions, and if » and y are the total increments of the horizontal force due 
to diurnal variation and disturbance at the time when the deflection and 
vibration experiments are made, 
H=H'—(9+¥)/2 
If C, and C, are the curve readings of the self-registering instrument 
at these times, 
H+¢=Z+C,, H+V=Z+4, ; 
Hythe pre zips 1+Cy 
