90 REPORT—1896. 
Hence the difference between the uncorrected value of the force, taken 
without reference to diurnal variation, &c., and the mean of the curve 
readings at the times of the two observations gives the reading corre- 
sponding to the zero line of the instrument. 
If, then, we write K and 8’ for H’, and C, and C for the correspond- 
ing means of the curve readings, we have as before : 
K=Z,+C), S'=Z+C; 
~.Z) —Z=K—C,—(S8’—C). 
Comparison of Magnetometer No. 70 with the Kew Standard Instrument. 
Horizontal Force. Observer: Professor RUcKeEr, 
i} | 
Instrument ol | ’ e = 
Date | Time and’ elie FEL Curve rina Me priaaa T hy ed = 
Giectention urve x10 x16 Z,—Z=pB 
H. M. | | | 
July 18] 12 4 | KV) 0:18280 | 0-18180) | 018196 +84 ia 
m4 14 89) =k DJ | 0-18213 J - | 000010 
< 12s37t\. SiaVi) 018290 | 018200) | 018196 +94) | 
_ 15 0 Ss Ds 0718193 f | 
ss 1550 | KD) 0:18292 | 0-18206) | 018208 +84 | ee 
z 1632 | K VJ | Q18211 f 000000 
x tient |e eS) aD) 018295 | 0-18207 018211 +84) | 
: 17°38) US “Vif o-isaic} | | 
July 20} 1232 | KV) 0:18289 | 018200) | 018204 +85 
¥ 1539 | kK Df 0:18208 f +0°00007 
* 1335 | S V) 0-18282 | 018209) | 018204 Werrene 
= 14 44 § Df | 0718200 f ; | —0:00013 
3 1646 | KD) 018286 | 0-18220) | O-lg221 +65 ) 
e 1729 | KV} | 0°18222 j 
July 22] 16 0 | K ra. 0°18301 | 018230) | 0-18298 +73 
. 1636 | KD 018227 j | 
= 17235 | 78°) 0:18297 | 0-18221) | 018290 +77 | —0-00004 
18°07). |L oS 018219 j 
| — 
Mean . _— _ | _ — — — — —0°00004 
Comparison of Magnetometer No. 70 with the Kew Standard Instrument. 
Horizontal Force. Observers: Professor Ricker and Mr. Watson. 
| Instrument } / <7 5 | 
Date Time and | H Curve ne K—G,—2,8 aCe Le 
Observation | urve | x10 | x10 io —L=B 
| | 
H. M | | 
Oct 9 14 14 K V | 0718256 0°18190 ) 018195 +61 
_ 14 52 K D 0718200 f 
Oct. 10) 1224 | K D) 018178) | 
a 15 30) K Vj 018263 | 0:18200- | 018189 +74 — 
a 15 56 J 018200) | | 
ss 14 18 S$ D) 0°18286 0°18193 ) 0°18196 | +90 | —0°00016 
te 14 51 s vf 018199) | 
* 16 18) Si) Vi). 018283 018206) | 018200 +83 —0°00022 
A 14 18) s D) 0718193 ) 
Oct. 12 ELC Saal iat = Balak Yh | 018290 0°18200 ) 0718203 +87 —0°00018 
Re 11 51 Ss Dj 0°18206 5 | 
= 13 14 K V) 018296 0718223) | 0718227 +69 | 
¥ 14 52 K Dj 0718232; | 
x 14 10 IN AT 0718288 0.18212 ) 0718222 +66 — 
‘s 14 52 K Dieu | 0°18232j | | 
Re 1151 } S D} |  0°18300 0718206 ) 0718216 | +84 —0:00018 
= 15 46 Ss Vj 0°18227 f 
| 
| 
Mean . — _ | — — } -—— — | — —0°00018 
As no observation was made with No. 70 on October 9, and as the 
earlier observations on October 10 were arranged so that the experiments 
