Hjorth's electromagnetic machine, 1849.
© Science Museum / Science & Society Picture Library
Plate taken from the 'Illustrated London News'. Soren Hjorth (1801-70), a Danish inventor, realised that the key to an efficient electric engine was a central generator, provided by a coil which rotates in the field of a magnet, thus producing a current. He speculated that this motor could utilise an electromagnet, powered by the electricity produced within the generator itself. The 'electromagnetic machine' he produced was exhibited at the 1851 exhibition, and, although it had no use in itself, prompted the reinvestigation of the concept of 'self-generation' in 1867 with more practical results.