242 M. Werner Siemens on the 
TABLE I. 
ik 2. 3. 4, 
Leg 90 millim. high. Leg 70 millim. high. 
Closed by Closed by 
keeper. Open. keeper. Open. 
Tnerease Increase Inerease Increase 
for x35 for yi5 for y35 for zd> 
Ampere ampere. ampere. ampere. ampere. 
0-01 800 800 195 195 1095 1095 140 #140 
0:03 3150 =1175 650 227 4800 1852 430 145 
0:05 6250 1550 | 1125 237 10500 2850 750 160 
007 (10500 2125 | 1640 257 20500 5000 | 1100 175 
0:09 {15500 2500 | 2165 262 33000 6200 | 1410 155 
O-1 18350 2850 | 2400 235 36200 38200 | 1570 160 
015 {37000 3730 | 3700 260 Pee ae 2390 164 
0-2 ee BAe 4830 226 ae a3 3100 =142 
0:25 ae gs 6000 234 = Ais 3900 160 
0:3 50 bbe 7100 220 ube Ag 4700 160 
0-4 ae Be 9600 250 a5 a 6200 150 
0-5 see oe 12250 8 265 ote te T9008 — 170 
The foregoing Table gives in the first column the observed 
current-strength, in the first column of each succeeding series 
the corresponding deflection, and in the second the increase 
of magnetic moment calculated from it for an increase in 
current-strength of 0-01 ampere, both in the open condition 
and when closed. ‘The result is, that in the closed horseshoe 
the magnetism at first increases in more rapid ratio than the 
current-strength. With the open magnet for feeble currents 
(0°05 ampere) the magnetism is about one fifth of the mag- 
netism produced by the like magnetizing force in the closed 
magnet; for the double current-strength (0-1 ampere) about 
one eighth. The increase of magnetism, on the other hand, 
is nearly constant with the open magnet, 7. e. the magnetism 
was nearly proportional to the current-strength up to the limit 
which the wire-coils permitted without too great heating. 
Next I cut 20 millim. off the projecting poles of the electro- 
magnet and repeated the experiments. As is seen in the 
third and fourth columns of the above Table, the magnetism 
of the closed magnet was much increased by this shortening 
of the poles ; whilst the magnetism of the open magnet de- 
creased in a still greater ratio, so that now for a current of 
0:05 ampere the above ratio has decreased to 7; and for 0-1 
ampere to ss. This disproportionately large decrease is evi- 
dently to be ascribed to the circumstance that not only has 
