316 



THE CENTURY BOOK OP FACTS. 



are sometimes called rt-gulated lamps. The 

 Brush patent is the arc light best known and 

 most used in America. In lights of the incan- 

 descent class a lighter current is used, and the 

 luminous substance is not consumed, being 

 inclosed in a sealed glass bulb from which the 

 air has been exhausted. It consists of a loop 

 of a thin fiber of some infusible substance (car- 

 bon has been found the best), inclosed in a 

 vacuum, as just stated. The ends of this fiber 

 are carried through the neck of the bulb and 

 connected with the opposite poles of the bat- 

 tery ; then the current, in passing through 

 such a small conductor, has to overcome a high 

 resistance, and in so doing generates a heat 

 sufficient to maintain the entire loop at a steady 

 temperature of white heat. The principal 

 forms of the incandescent light are those of 

 Edison, Swan, Maxim, and Siemens. It is 

 perhaps worthy of note that the great impetus 

 given to electric lighting by the work of Thomas 

 Edison has been not so much in improving the 

 lamp as in cheapening the process of generat- 

 ing the electricity and inventing a ready mode 

 of dividing the light. Hitherto the two prin- 

 cipal barriers in the way of applying the electric 

 light to public use had been the expense at- 

 tendant upon the production of the electric 

 force and the difficulty of using it simulta- 

 neously at a large number of illuminating 

 points. 



Electricity As far back as 321 B. C., 



the ancient philosopher Theophrastus men- 

 tions the power of am'ber to attract straws and 

 dry leaves. Pliny, in 70 A. D., writes con- 

 cerning the same phenomenon, and it is from 

 the Greek name of "amber," pronounced 

 "electron," that we call this phenomenon 

 "electricity." Dr. Gilbert, of Colchester, 

 may be considered the founder of the science 

 of electricity, for it was he that carefully re- 

 peated the observations of the ancients, and 

 experimented in various ways and published 

 these experiments in a book during the period 

 between 1540 and 1603. Sir William Watson 

 (1715 to 1807) distinctly announced the theory 

 of positive and negative electricity, which was 

 afterwards elaborated by Dr. Benjamin Frank- 

 lin. . Dr. Franklin also established the fact 

 that the lightning was an electrical spark, 

 similar to that made by an electric machine or 

 Leyden jar. In 1790, Galvani discovered that 

 the contact of metals produced muscular con- 

 traction in the legs of a dead frog, and in 1800, 

 Volta discovered the art of generating elec- 

 tricity by contact of metals with damp cloths. 

 From these we obtained the galvanic battery 

 and the voltaic pile. 



It remained with Prof. II. C. Oersted, of 

 Copenhagen, however, to bring forward the 



most important fact, viz. : the magnetic action 

 of the electrical current. This was in 1820. 

 As soon as the discovery reached France, the 

 eminent French philosopher Ampere set to 

 work to develop the important consequences it 

 involved. Faraday in 1820, discovered electric- 

 magnetic rotation. From this time up, exper- 

 imentists and theorists were busy searching 

 for ways and means by which the electrical 

 energy could be utilized as a mechanical power, 

 and to-day the galvanic battery and electric 

 dynamo are rapidly ousting steam, and in a 

 thousand ways doing its work with less noise, 

 expense, and better results. 



As to the question of the real nature of 

 electricity, recent experiments and further 

 knowledge of its properties rather open fresh 

 avenues to new hypotheses than point to the 

 truth of any one special theory. Some iden- 

 tify electricity with energy, some with matter, 

 and some with the subtle all-pervading 

 ' ' ether. ' ' At all events it has been computed 

 that in every single cubic foot of ether there 

 are locked up 10,000 foot-tons of energy ! The 

 latest researches give well-founded hopes that 

 this inconceivably vast storehouse* of power 

 will one day be accessible to man. And here- 

 in lies the splendid possibility of a new and 

 mighty successor to the decreasing energy of 

 our coal-fields, with the speedy extinction of 

 which alarmists threaten us. By creating in 

 a room a powerful electrostatic field alternat- 

 ing very rapidly, Professor Nicola Tesla 

 brought it to such a state that illuminating 

 appliances could be placed anywhere, and kept 

 lighted without being electrically connected 

 with anything ! He suspended two sheets of 

 metal, each connected with a terminal of the 

 electric coil, between which an exhausted tube, 

 carried anywhither, remained always lumi- 

 nous. A true flame can now therefore be pro- 

 duced without chemical aid a flame yielding 

 light and heat without the consumption of ma- 

 terial or any chemical process ! Further, 

 these and similar experiments on electric radia- 

 tion, which now advances so brilliantly to the 

 forefront, by Tesla and Crookes, etc., point to 

 the bewildering possibility of telegraphy with- 

 out wires, without cables, without posts. 

 There is considerable evidence to show that, 

 could the electric ether-waves be obtained suffi- 

 ciently short, the rays would fall within the 

 limits of visibility, and thus place the final 

 crown of proof on the magnificent experiments 

 of Hertz and others, who would make light an 

 electric phenomenon. 



As regards the effect on the human body of 

 alternating currents of very high frequency 

 (which at best have a very doubtful reputa- 

 tion) it has been found that, as the rapidity of 



