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

19 Current in amperes.......... 23,8 22,4 17,5 14,3 Resistance in the external cir- cuit in ohms............... 3,6 3,9 6,2 8,7 Speed of dynamo, number of rotations per minute....... 744 790 848 930 In order to determine the efficiency of the lamp, that is, the number of standard candles illuminating power per horse-power electrically given to the lamp, the current passing through it was measured in amperes, the electromotive force between the terminals in volts, and simultaneously the illuminating power. The beam of light coming at different angles in succession from the lamp was received in the photometer, and several measurements were made at each angle. Nega- tive angles mean that the lamp was below the photometer, and therefore sending rays up, while the positive sign before the angle indicates that the lamp was above the photometer and therefore sending the rays down. The light was examined through red glass as well as through green glass, in order to compare its inten- sity with the red light of a standard candle and with the green light. The more important of the results of the measure- ments are contained in the following table: 2*