ELECTRIC LIGHT 



modern methods of warfare would. have to be 

 almost entirely changed. 



Electricity in Medicine. The beneficial ef- 

 fects of electricity in stimulating the nerve 

 cells and .thus securing greater activity in the 

 various organs and tissues of the body has 

 long been known, but the use of electric energy 

 in medicine has been extended far beyond 

 this limit. In surgery it is used to destroy 

 tumors and diseased tissue, for removing birth- 

 marks and superfluous hair and for cauterizing 

 wounds. Besides these uses there are others 

 peculiar to the X-ray, which are described un- 

 der the title ROENTGEN RAYS. W.F.R. 



Consult Burns's Electric Motor; Burns's Alter- 

 nating Currents Simplified; Durgin's Electricity, 

 Its History and Development; Campbell's Prin- 

 ciples of Electricity; Mlllikan's Practical Les- 

 sons in Electricity. 



Related Subjects. The above article with its 

 numerous subtitles does not much more than lay 

 the foundation for the treatment given to elec- 

 tricity in these volumes. The following articles 

 will be of interest in this connection : 

 Armature Electroscope 



Cathode Rays Electrotyping 



Crookes Tubes Faraday, Michael 



Current Galvanic Battery 



Davy, Sir Humphry Galvanism 

 Dielectric Galvanometer 



Dynamo Induction, Electric 



Edison, Thomas A. Induction Coil 



Electric Battery Insulator 



Electric Bell Kilowatt 



Electric Heating Lightning 



Electric Light Locomotive (subhead 



Electric Machine Electric Locomotive) 



Electric Meter Magnet and Magnetism 



Electric Motor Marconi, Guglielmo 



Electric Railway Ohm 



Electric Welding Roentgen Rays 



Electrochemistry Storage Battery 



Electrocution Telegraph 



Electrode Telephone 



Electrolysis Thermoelectricity 



Electromagnet Vacuum Cleaner 



Electromagnetic Theory Volt 



of Light Volta, Alessandro 



Electromagnetism Voltaic Pile 



Electrometer Watt 



Electromotive Force Wireless Telegraph 

 Electroplating 



ELECTRIC, elek'trik, LIGHT, a light pro- 

 duced by an electric current, a development 

 of the latter part of the nineteenth century. 

 Few people realize the extent to which electric 

 light has changed the face of the earth, within 

 the memory of fully one-third of the people 

 yet living in the highly-civilized nations. Early 

 in the nineteenth century men carried lanterns 

 to find their way along city streets at night; 

 later, illuminating gas was hailed as a great 

 improvement, and prophets were dreaming of 



the time when a city might be as light by night 

 as by day. 



The electric machine produces a flash of light 

 which lasts only a fraction of a second. This 

 fact led inventors in the first decade of the 

 nineteenth century to seek a means of pro- 

 ducing a steady electric light. The earliest at- 

 tempt that gave even a faint promise of suc- 

 cess was that of Sir Humphry Davy, who 

 with a battery of hundreds of cells produced 

 an electric arc ; the cost, however, was so great 

 that this method of lighting was not thought 

 practical. This was in 1813. In 1858 a light 

 sufficiently strong for lighthouses was pro- 

 duced by means of magneto-electric genera- 

 tors. With the invention of the dynamo of 

 Werner von Siemens and Zenobe Theophile 

 Gramme, in 1866 to 1868, the system of arc 

 lighting was greatly improved. The light could 

 be used where a single powerful light was 

 needed, as in a lighthouse or on city streets, 

 but it was not suitable fof house lighting. The 

 invention of a practical incandescent light by 

 Thomas A. Edison in 1878-1879 made it possi- 

 ble for the first time to have a large number 

 of small electric lights suitable for use in 

 houses. 



The Incandescent Light. The ordinary in- 

 candescent light has a strange history. Soon 

 after the discovery 

 of the electric bat- 

 tery it was found 

 that an electric cur- 

 rent flowing through 

 a wire will heat the 

 wire, and if the cur- 

 rent is strong 

 enough the wire will 

 become white hot 

 and give out light. 

 Here, then, was a 

 means of producing 

 electric light, but 

 what kind of wire 

 should be used? 

 Platinum has high 

 resistance and is 

 easily heated to a 

 white heat, but the 

 platinum lamp when 

 tried was found to CARBON LAMP 



t Now largely abandoned 



be too expensive, j n f av0 r of more powerful 



both to manufac- l*ht *" le88 C08t - 

 ture and to operate. Carbon has high resist- 

 ance and also is easily brought to a white heat, 

 but a carbon filament made white hot in air 



