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A HISTORY OF ENGINEERING I
stored in an electric accumulator which needs recharging from time to time. This method was first adopted for public transport in Paris in 1882, and in this country in Birmingham in 1890, but its use for this purpose has not only been limited, but of doubtful success, mainly on account of the great weight of accumulators per unit of power, and the fact that they continually require recharging. At the present day this type of electric traction proves useful for small trolleys for the handling of goods over short distances in factories, wharves, etc., and for electric broughams. I I I . — E L E C T R I C L I G H T I N G A N D P O W E R G E N E R A T I O N AND DISTRIBUTION
The history of the early years of electrical development is almost entirely a history of electric lighting. The first electrical machines invented were used to supply electric power for illumination. Sir Humphrey Davy in 1801 first suggested the conversion of electrical energy into a luminant. He noticed that when an electric circuit was broken an electric spark was produced, and provided the broken ends were not taken too far apart, the arc continued. With a view to investigating this effect further Davy in 1808 requested a large voltaic battery from the managers of the Royal Institution of Great Britain, and he was provided with a large battery of 2,000 cells. The arc was made between the tips of two pieces of carbon, and an exceedingly brilliant light was obtained, but no practical application of this principle of lighting was made. Subsequent to the work of Faraday, Holmes, in 1857, had a permanent magnet machine constructed for the Trinity Board, and it was tested at Blackwall by Faraday. The results were good, and two larger machines were built with which, in 1858, carbon arc electric light was produced and was exhibited at sea for the first time at the South Foreland Lighthouse. These machines were afterwards removed to the Dungeness Lighthouse. Other machines of the same design and for the same purpose were later constructed by Holmes. In 1863 H. Wilde of Manchester took out a patent for a machine in which electro-magnets were excited by means of a battery. Wilde constructed a large machine on this principle fundacion juanelo * turriano