108 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
in the iron core, nevertheless some direct experiments were made to test this 
point. 
A horse-shoe electro-magnet, weighing 1854 grains (0'265 lb.), surrounded with 
1102 yards of insulated copper wire of 0 - 014 inch diameter, in 4352 turns and 34 layers, 
and presenting a total resistance of 200 ohms, consequently very small in comparison 
with the internal resistance of the batteries, was employed in making the experiments. 
The armature was suspended on a delicately-poised steel-yard, accurately divided, and 
provided with a suspender for the weight, mounted on rollers to permit of its being 
moved smoothly along the long arm of the lever, so as not to give any shock which 
might disturb the armature. 
Observations were made of the weight supported by the magnet when 1200, 2400, 
and 3600 cells were used, the current passing in each case being at the same time 
measured by a galvanometer, the value of whose deflections had been determined in 
absolute units of current. The following results show that the weight supported by 
an electro-magnet was not merely proportional to the current, but increased with the 
number of cells : — - 
Col. 3. 
Number of cells 
Current 
Weight supported 
Col. 2. 
Ratio to 1200 cells 
(col. 1). 
(col. 2). 
(col. 3). 
Weight in lbs. 
as unity. 
Weber. 
lbs. 
per Weber. 
1200 
0-09443 
26-6 
281-6 
1-000 
2400 
0-09261 
32-3 
340-9 
1-211 
3600 
0-08298 
31-5 
379"6 
1-348 
Other experiments 
were made 
with an electro-: 
magnet formed of the same core, but 
with the substitution of coils composed in all of 37 '6 yards of insulated copper wire, 
0‘052 inch diameter, 
in 246 turns, and having a 
resistance of 0"6 
ohm. The results 
obtained confirm the statement that the weight supported increases with the number 
of cells for the same 
current : — 
Col. 3. 
Number of cells 
Current 
W eight supported 
Col. 2. 
Ratio to 1200 cells 
(col. 1). 
(col. 2). 
(col. 3). 
Weight in oz. 
as unity. 
Weber. 
oz. 
per Weber. 
1200 
0-10660 
66 
619-0 
1-000 
2400 
0-08898 
63 
707-9 
1-144 
3600 
0-08399 
62 
738-2 
1-192 
This electro-magnet, with the last-named coil composed of 3 7 - 6 yards, supported 
42 pounds when the zinc-carbon battery of six cells in series, described at page 92, 
was connected with it, giving a current of 14'35 Webers. The weight divided by the 
current comes out 46 '8 as the weight in ounces per Weber. The foregoing results 
must not be accepted as final, as the experiments will be repeated at a future 
opportunity. 
