M. J. Nicklés on a New System of Electro-magnets. 381 
lengths, as follows: 
: Millimeters. __ Millimeters, 
No. 1. 0-050 long, No. 3. 0°150 long. 
No. 2. 0-100 long. No, 4. 0200 long. 
The helix consists of 94 metres of copper wire, a millimeter in 
section, forming a coil of 754 turns. Cylinder No. 3 was plac 
in the helix. The weights are given in grammes. 
aS Tang. 11° 20 Tang. 7° 15/ 
are bs pet a me ba AR og 
0, 1700 gr. 1750 0. 9 
No. 1 No. ‘1. 1100 50 
0 2, 2000 2150 | No. 2. 1210 1250 
No. 3 2150 2940 | No. 3 1260 1300 
3+1 2250 2290 | 3+1 1300 ~—«- 1320 
842, 2290 2300 342. 1320 1340 
No. 6. 2300 Mei @ 1340 1340-45 
The influence of the clongation of the magnetic bar upon the 
attraction is obvious. Nevertheless it has its limit, from which 
it the attraction diminishes as the length of the magnet in- 
teases. This is shown in the following table, in which the 
same method was adopted, but with a more feeble current. 
Tang. 11° 20’ 
Length added, * Weight lifted. Weight falls. 
0. 720 * 800 
1 5 1000 
No. 2, 1000 1170 
No. 3. 1050 1140 
No. 4. 1150 1 
No, 5, 1050 1200 
No. 6. 1050 . 1210 
6-1. 1 : 1170 
6-+-2. ‘ 950 000 
6+-4, ‘ 960 990 
6+7. 890 ; 940 
. It is here apparent that the attraction decreases from No. 5. It 
8 also seen that the decrease is more rapid when the bar is made 
of two or more pieces, instead of being in a single solid piece. 
This fact, which I have established in various ways, is of great 
the construction of electro-magnets. 
