Notice sur des Expériences exécutées avec la Machine Dynamo-électrique
et avec la Lampe á arc Voltaïque de M. Jürgensen

15 tically enabling them to produce a stronger magnetic field for the same strength of current and number of convolutions of wire. Both these specialities in the machine are advan- tageous in enabling a strong magnetic field to be created, and therefore a high electro-motive force. We made certain tests of the current and electro- motive force produced by the machine running at diffe- rent speeds, 1st, when two arc lamps were in circuit; 2nd, when one arc lamp was in circuit; and lastly, when various resistances were introduced, and the following are the results we obtained: | No. of revolutions per minute. Current in amperes. Electromotive force । in volts between the terminals of machine. Approximate total electromotive force of the machine. Resistance in the 1 external circuit in Ohms. Remarks. 800 840 550 17,3 18,1 15,4 78,3 97,2 58,o 12G 148 101 2 arc lamps burning in circuit. One „ B „ 620 G10 620 560 630 14,3 16,4 20,7 24,3 25,8 65,3 54,5 43,8 28,i 29,o 106 103 102 97 103 4,5 3,3 2.i 1,2 1»» If the last set of observations be reduced all to the same speed, 620 revolutions per minute, the total electromotive force becomes: 106 volts, 105 — 102 — 107 — 101 —