54 On Recent Improvements in Electric Lighting. 



The first introduction of the electric light is, of course, to 

 be dated back to seventy-two years ago, or in 1808, when Sir 

 H. Davy first exhibited the light by means of his powerful 

 battery of two thousand pairs of plates. This light was 

 improved in 1810, and from that date to the present time 

 but little improvement may be said to have taken place in 

 the use of the voltaic current as a practical generator of 

 electricity for illuminating purposes. I think any one who 

 has had experience in fitting up and attending to a battery 

 of the requisite size for such a purpose will agree that, to 

 say nothing of the expense of working and maintaining, 

 the trouble of keeping it in order would preclude its 

 becoming available for any other than temporary pur- 

 poses, such as lectures, &c, or where, perhaps, a small 

 light for photographic use might be required, for which a 

 battery of eight Bichromate cells of an improved con- 

 struction, in which the solution is kept agitated by a 

 current of air, has recently been introduced, it is said, in a 

 perfectly practical form. Whilst we are not able, therefore, 

 to recognise the ordinary battery as an efficient or practical 

 generator of the current, I may mention that a thermo- 

 electric battery has been introduced by M. Clamond, formed 

 of iron as the positive and antimony and zinc as the negative 

 elements, and that it has been used for lighting a workshop 

 with great success. The size given is about 8 feet high by 

 3 feet 3 inches diameter; the electro-motive force is given as 

 being equal to 120 Bunsen cells, and giving a light of about 

 1000 candles ; the internal resistance of the battery is stated 

 to be 031 Ohms, and it consumes about 22 lbs. of coke per 

 hour. I am unable to give any more information on this 

 matter ; but from what we already know relative to thermo- 

 electric batteries, they do not possess the requisite stability 

 for lighting purposes. We may, therefore, pass on at once to 

 the principles by which the necessary amount of current for 

 our purpose can be produced efficiently and economically. 



In 1831 Faraday made known the fact that if a helix, or 

 coil of insulated wire, was moved or rotated in front of a 

 permanent magnet, a current of electricity was induced in 

 the coils, and that by suitable arrangements it could be used 

 in the place of an ordinary battery. 



Very many magneto machines, as they are called, were 

 constructed of different forms ; the ordinary kind used for 

 medical purposes at the present time is but a modification 

 of Faraday's discovery. In 1854 Siemens introduced an 



