Mr Barlow on the Laws of Electro- Magnetic Action. IIS 
Experiments on the relative Electro-Magnetic Effect qfdi^ereni 
sized Copper-Wires. 
Weight 
of the 
Specimen 
in Grains. 
Deflection 
produced 
by Stand- 
ard Wire 
1st Trial. 
Deflection 
produced 
by Stand- 
ard Wire 
2d Trial. 
‘Mean 
Deflection 
by 
Standard. 
Deflection 
produced 
by the 
Specimen. 
O 
Q 
0 
0 
17 
39 
37 
38 
25 
' 49 
35 
33 
34 
31 
59 
33 
31 
32 
28 
70 
31 
284 
29| 
28 
95 
284 
' 274 
28 
26 
140 
274 
264 
27 
26 
180 
264 
24 
254 
254 
250 
224 
23 
22| 
23 
290 
23 
21 
22 
22 
580 
20 
21 
204 
21 
1350 
21 
20 
204 
20 
1590 
20 
194 
19| 
194 
Experiments on the relative Electro-Magnetic Effect of different 
sized Brass-Wires. 
Weight 
of the 
Specimen 
in Grains. 
Deflection 
produced 
by Stand- 
ard Wire ' 
1st Trial. 
Deflection 
produced 
by Stand- 
ard Wire 
2d Trial. 
Mean 
Deflection 
standard. 
Deflection 
produced 
by the 
Specimen. 
0 
0 
0 
0 
38 
33 
30 
314 
264 
44 
30 
29 
294 
24 
80 
29 
28 
284 
26 
100 
28 
27 
274 
234 
150 
27 
26 
264 
25 
250 
26 
254 
25| 
254 
470 
254 
24 
24| 
24 
680 
24 
234 
23f 
234 
1330 
23 
22 
224 
22 
1580 
22 
21 
214 
22 
1890 
21 
2D 
21 
22 
3770 
21 
21 
21 
214 
On a comparison of these several results, it will be seen, that, 
while the conducting wire weighed less than about 1 80 grains to 
the two feet in length, its effect on the needle was in defect, in 
comparison with that of the standard, which weighed 470 grains ; 
but that no power was either gained or lost after this, although 
wire was employed weighing nearly 4000 grains, which appears 
to be consistent with the deductions made by Professor Cum- 
VOL. XII. NO. S3. JANUARY 18S5. 
H 
