610 LEN2 ON ELECTRO-MAGNETISM. 



luyself of this by the identity of the results in several repetitions of the 

 experiment. This also showed me that the electromotive power of the 

 magnet, at least after having already undergone several removals, did 

 not become weaker ; proofs of this will also be furnished in some expe- 

 riments hereafter to be mentioned. In the above-described arrange- 

 ment of the apparatus, I could now with the right hand perform the 

 removal of the armature from the magnet, which was fixed to a table, 

 while at the same time my eye observed in the telescope the consequent 

 deviation of the index of the multiplier. This index was a thin lath, 

 which was fixed by means of some wax to the wire which served as a 

 common axis for the two needles of the multiplier, and formed a dia- 

 meter of the graduated circle. Being thus able to observe the deviation 

 for every result which was to be deduced therefrom, first on the one 

 and then on the other end of the index, I freed this result from the in- 

 fluence of the eccentricity of the axis of the needles, and turning first 

 the end A and then the end B of the spirals towards the north arm of 

 the magnet, and allowing the needles of the multiplier to deviate 

 first on the one side then on the other, I made the result independent 

 of a second error which arises if the cocoon threads to which the needles 

 of the multiplier are suspended possess a rotatory motion. Further, I 

 carefully avoided every disturbance of the multiplier during a series of 

 combined experiments, because it is impossible that every coil of the 

 multiplier could act in the same manner as another (this would pre- 

 suppose that they were all in the same plane, and parallel to one an- 

 other), and because even if this might be presupposed, the action would 

 still vary according as the needle when stationary might be exactly 

 parallel to the coils, or form a greater or less angle. The positions of 

 the needles when at rest seldom dilFer more than 0**3 from one another. 

 According to the above statement, a complete experiment always de- 

 manded four observations, namely, two (at both ends of the hand) for 

 the position where the end A of the spiral was turned to the north pole, 

 and two where B was directed to the north pole. Besides this I have 

 repeated almost every experiment twice over in order to convince 

 myself that no accidental fault had crept into the reading off; if the 

 two observations differed much from one another, I again repeated 

 each of them. The first preparatorj^ experiments were made on 

 the influence of the combinations of the conducting wires with the 

 electromotive spirals and with the wires of the multiplier, in order 

 to see whether I should content myself with winding the ends of the 

 wires, w hich had been freed from their silk and were clean, very closely 

 round one another, or should be obliged to produce a closer connection, 

 for instance by immersing them in quicksilver. I proceeded on the 

 supposition that il the connection effected by winding them many times 

 closely round one another was not sufficient, an increase of convolutions 



