140 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXIX.) 
deflection, but such is not the case here. The currents observed are for short 
periods, and they give, as it were, a blow or push to the needle, the effect of which, in 
swinging the needle, continues to increase the extent of the deflection long after the 
current is over. Nevertheless the extent of the swing is dependent on the electricity 
which passed in that brief current ; and, as the experiments seem to indicate, is simply 
proportional to it, whether the electricity pass in a longer or a shorter time (3104.), 
and notwithstanding the comparative variability of the current in strength during the 
time of its continuance. 
3186. The compound bar being introduced once into the loop and left there, the 
swing at the galvanometer was observed and found to be 16°; the galvanometer 
needle was then brought to zero, and the bar removed, which gave a reverse current 
and swing, and this also was 16°. Many alternations, as before described, gave 16° 
as the mean result, i. e. the result of one intersection of the lines of force of this mag- 
net (3102.). In order to comprehend the manner in which the efiect of two or more 
intersections of these lines of force were added together, it should be remembered 
that a swing of the needle from right to left occupied some time (13 seconds) ; so 
that one is able to introduce the magnet into the loop, then break the electric cir- 
cuit by raising one end of the communicating wire out of the mercury, remove the 
magnet, which by this motion does nothing, restore the mercury contact, and reintro- 
duce the magnet into the loop, before a tenth part of the time has passed, during 
which the needles, urged by the first impulse, would swing. In this way two im- 
pulses could be added together, and their joint effect on the needle observed ; and, 
indeed, by practice, three and even four impulses could be given within the needful 
time, i. e. within one-half or two-thirds of the time of the full swing ; but of course 
the latter impulses would have less power upon the needles, because these would be 
more or less oblique to the current in the copper coil at the time when the impulses 
were given. There can be no doubt, that, as regarded the currents induced in the 
loop by the magnet, they would be equal on every introduction of the same magnet. 
3187. Proceeding in this way I obtained results for one, two, three, and even four 
introductions with the same magnet. 
, o 
One introduction 15 
Two introductions 31-25 
Three introductions 46*87 
Four introductions 58*50 
Here the approximation to 1, 2, 3, 4 cannot escape observation* ; and I may remark, 
* See note to (.3189.) sin ^ =sin 7 30 ='130526 
31-25 
sin — ^ = sin 15'625 = sin 15 37'5 = '269200 
sinl^^ = sin 23'435= sin 23 26'1 = '3976818 
sin ^^= sin 29-25 = sin 27 15 ='4886212 
'130526 
269-200 
2 
3976818 
= •134600 
3 
4886212 
= •1328606 
= •1221553 
