148 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXIX.) 
results is 8°’94, and is again an increase on the effect produced by the preceding 
rectangle of wire, only half the diameter of the present. This thickness of wire was 
also employed formerly as a loop (3136.) ; and if we compare the results then obtained 
with the present results, it is remarkable how near they approach to each other ; a 
circumstance which leads to great confidence in the principles and practice of both 
forms of examination. When wires having masses in the proportion of 1 : 4 and 16 
were employed as loops, the currents indicated by the galvanometer were as TOO, 
2‘77 j and 3*58 ; now that they are employed as rectangles subject to the earth’s mag- 
netic power, they are as TOO, 2*78, and 3*45*. 
3206. I formed a square, 12 inches in the side, of four convolutions of copper wire 
0*05 of an inch in diameter; the single wire which formed it was consequently 
16 feet long. Such a rectangle will, in revolving, intersect the same number of lines 
of magnetic force as the former rectangle made with wire 0*1 in diameter (3203.) ; there 
will also be the same mass of wire intersecting the lines, but, as a conductor, the first 
wire has in respect of diameter, only one-fourth the conducting power of the second ; 
and then, to increase the obstruction, it is four times as long. Six direct revolutions 
gave an average result of 20°*6, and six reverse revolutions 19°*7 ; the mean is 20°*15, 
and the proportion per revolution 3°*36. With the other rectangle having equal 
area and mass, but a single wire (3203.), the result per revolution was 7°‘26 ; being 
above, though near upon twice as much as in the present case. Hence for such an 
excellent conducting galvanometer as that described (3123. 3178.), the moving wire 
had better be as one single thick wire rather than as many convolutions of a thin one. 
If it be, under all variations of circumstances, the same wire for the same area, then, 
of course, two or more convolutions are better than one. 
3207 . It was to be expected, however, that the thin wire rectangle would produce 
a current of more intensity than that in the thick wire, though less in quantity ; and 
to prove this point experimentally, I connected the two rectangles in succession with 
Ruhmkorff’s galvanometer (3086.), having wire only xlrth of an inch in diameter. 
That of the single thick wire now gave only 1°*66 of swing for twelve revolutions of 
the rectangle, or 0°*138 per revolution ; whilst the other of four convolutions of thin 
* sm^Z^=.sinl3°-52=sinl3°31'-2=-2337848 '^ii^^=-0779283. The square 12 inches side, 
2 2 
of wire 0'05 in diameter, gave for’six revolutions (3196. 3197.) '0227057 as sin i A for one revolution. 
A like square of wire O'lO in diameter gave for five revolutions (3021.) — ='06451428 as sin - A 
for one revolution. A like square of wire 0'20 in diameter gave '0779283 as sin i A for one revolution 
'06451428_^.ojj •0779283_.,.^.,^ 
-0227057 ■ -0227057 
