M. A. F. Sundell on Galvanic Induction, 285 



gently in an incision on the handle, whereby the experiment 

 could be stopped after a certain number of turns. Usually five 

 turns were made in an experiment ; the amplitude of the first 

 deflection that the eighty secondary currents produced in the 

 magnetometer was taken as a relative measure of the strength 

 of induction. The amplitude was observed with a telescope 

 and a millimetre-scale by means of the mirror fixed to the mag- 

 netic needle. Whenever the handle was turned more or less 

 than five times, the observed deflection was reduced to that for 

 eighty currents. The conducting-power of the secondary cir- 

 cuit was measured by means of a magnet inductor. Before the 

 commencement of an experiment the wheels of the disjunctor 

 were always in such a position as to complete the primary cir- 

 cuit. The wires from the battery, the coils, and the magneto- 

 meter were twisted together two by two, or went parallel a short 

 distance. Thus every other inducing effect, except that between 

 the coils, was prevented. 



2. We will relate the series of experiments in the order 

 in which they were made. The following designations may be 

 used : — i represents the intensity of the primary current ; m the 

 number of windings in the primary coil, and n that in the se- 

 condary coil; /the conducting-power of the secondary circuit, 

 and J the first deflection of the needle of the magnetometer for 

 eighty currents. The distance between the coils, denoted by z t 

 is estimated from the plane of the middle winding in the one to 

 the corresponding plane in the other coil. 



Series 1. One of the large coils was taken as primary, 

 and one of [the small as secondary coil, « = tanl5°, m = 31, 

 n = 51. The current induced by the magnet inductor deflected 

 the needle of the magnetometer eighty-seven divisions of the 

 scale ; accordingly /= 87. 



z (centimetres) 

 J (divisions of the 



scale) 



8. 

 25 

 48-0 

 47-6 



1. 2. 

 15 20 

 93 4 65-2 

 93-6 65-0 

 93-2 . . . 



3. 

 25 

 46-0 

 45-6 



4. 

 30 

 32-8 

 32-0 

 32-8 



5. 6. 

 40 40 

 17-8 180 

 17-4 18-4 



J (mean) . . 



7. 

 z . . 30 

 J . . 35-0 

 35-2 



93-4 65-1 



9. 

 20 

 67-0 

 67-2 



45-8 



10. 

 15 

 93-4 

 93-0 



325 



11. 



10 

 127-5 

 127-3 

 127-5 



17-6 18-2 



12. 

 1-5 

 176-5 

 175-5 



J (mean) 35-1 47'8 67'1 93\2 127*4 

 If the arithmetical mean of the deflections corre 



1760 



sponding to 



