126 SCIENCE IK SHORT CHAPTERS. 



independently, I believe), and which, with modifications, has 

 since been rather extensively used. 



Although successful so far, he was not satisfied. He reasoned 

 out the subject, and concluded that the electric spark between 

 metals, the electric arc between the carbons, and other lumi- 

 nous electric phenomena are secondary effects due to the heating 

 and illumination of electric carriers ; that the electric spark of 

 the conductors of ordinary electrical machines is e-imply a trans- 

 fer of incandescent particles of metal, which effect a kind of 

 electric convection, known as the disruptive discharge ; and 

 that the more brilliant arc between the carbon points is simply 

 due to the use of a substance which breaks up more readily, 

 and gives a longer, broader, and more continuous stream of 

 incandescent convection particles. 



This is now readily accepted, but at that time was only 

 dawning upon the understanding of electricians. I am satis- 

 fied that Mr. Starr worked out the principle quite originally. 

 He therefore concluded that, the light being due to solid parti- 

 cles heated by electric disturbance, it would be more advanta- 

 geous as regards steadiness, economy, and simplicity to 

 place in the current a continuous solid barrier, which should 

 present sufficient resistance to its passage to become bodily 

 incandescent without disruption. 



This was the essence of the invention specified in King's 

 Patent as " a communication from abroad," which claims the 

 use of continuous metallic and carbon conductors, intensely 

 heated by the passage of a current of electricity, for the pur- 

 poses of illumination. 



The metal selected was platinum, which, as the specification 

 states, " though not so infusible as iridiurn, has but little affin- 

 ity for oxygen, and offers a great resistance to the passage of 

 the current. " The form of thin sheets known by the name 

 of leaf -platinum is described as preferable. These to be rolled 

 between sheets of copper in order to secure uniformity, and to 

 be carefully cut in strips of equal width, and with a clean edge, 

 in order that one part may not be fused before the other parts 

 have obtained a sufficiently high temperature to produce a brill- 

 iant light. This strip to be suspended between forceps. 



I need not describe the arrangement for regulating the dis- 

 tance between the forceps, for directing the current, etc., as 

 we soon learned that this part of the invention was of no prac- 

 tical value, on account of the narrow margin between efficient 

 incandescence and the fusion of the platinum. The experi- 



