250 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 3 



While electricity can be produced in a variety of ways, and it was 

 some time in the history of the subject before it was realized that the 

 electricity was the same kind of thing in all of these cases, neverthe- 

 less there are but three principal means of generating electricity. 

 The first is static electricity, first discovered by Thales of Miletus as 

 early as 600 B.C. Thales found that amber, when rubbed against 

 other substances, had the power of attracting fragments of straw or 

 leaves or feathers. In fact, the word electricity is derived from the 

 Greek word electrum, meaning amber, and was first so used by 

 William Gilbert in about 1600. 



The second great step in the production of electricity was the inven- 

 tion by Volta of the voltaic cell in 1799, and from that time until the 

 time of Faraday in 1831, the great development of electricity was in 

 the production of batteries of various kinds. Volta was able to gen- 

 erate several hundred volts by piling up alternate layers of copper 

 and zinc, separated by paper which had been moistened with acid, 

 thus creating, in effect, a battery with a large number of cells in 

 series. 



When in 1831 Faraday made the discovery of electromagnetic in- 

 duction and about the same time Joseph Henry discovered self- 

 induction and independently repeated a number of Faraday's dis- 

 coveries in mutual induction, the modern science of electricity and 

 art of electrical engineering were born. 



It is a striking fact, which perhaps we do not stop to think about, 

 that this so-called " electrical age " has grown up during a period of 

 one working lifetime, since men like Elihu Thomson are still living 

 and men like Edison have just died, who built upon these scientific 

 discoveries of Faraday and of Henry the modern art of electrical 

 engineering. 



With the development of electromagnetic devices, dynamos, mo- 

 tors, and transformers, the use of batteries, except for very special 

 purposes, has largely been discontinued. Static electricity, which 

 had been developed from the study of frictional charges and charges 

 of conductors by induction, was relegated almost to the field of 

 scientific but useless curiosities. The efficiency of electromagnetic 

 generating apparatus has been developed to a remarkable degree, so 

 that for the practical purposes of our industrial needs and our home 

 needs the modern science of electricity has appeared to be eminently 

 satisfactory. 



It is true that there have been some other new developments of 

 first importance in the electrical field, notably electronic devices, such 

 as radio-tube detectors, amplifiers, and transmitters or devices which 

 operate with ionization of gases, such as the mercury-arc rectifier and 

 the glow discharge tube. These things, however, are more in the 



