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

21 The lamp burnt steadily, and with proper resi- stances given to the three solenoids the feed of the carbons could be made extremely regular, and the light therefore very constant. (Signed). W. E. Ayrton. John Perry. The machine, that was subjected to the tests, is constructed to produce 2 lights of 2000 candle-power each, it is comparatively small, its base being 28^2 inches in length, and 21 Va inches in width, across its middle (the widest part). The armature is about IOV2 inches in diameter, and the length from end to end of the supporting rings, 9 inches. With a large machine, manufactured for the danish Government to be employed at the naval forts at Co- penhagen, experiments were made in November 1882 to compare its efficiency with that of a large dynamo- machine of Gramme, manufactured by Sautter, Lemon- nier & Co. at Paris. The Gramme machine at a speed of 475 revolutions per minute produces a light of 4000 bees Carcel. The french dynamo had been established for some time at the fort „Prøvesteen“, it was actuated by a steam-engine of the system of Brotherhood of 14 horse-power, the steam being taken from a ship-boiler, established in a Casemate in masonry. The danish dy- namo was actuated by a similar steam-engine of Brother- hood, the steam being taken from the same boiler by means of a special steam-tube. At a speed of 420 revolutions per minute*) this ) Without doubt this speed somewhat surpasses the speed, that makes the machine develop the greatest efficiency, by a speed of about 360 revolutions per minute the result obtained un-