KKC'OKDR OK MKKTINGS. 



393 



Committee, stated the grounds for the award of the Rumford 

 Premium to Professor Tlieodore Lyniau, of Cambridge, as fol- 

 lows : — 



The Rumford Premiimi has been awarded by the Academy to 

 Professor Lyman "for his researches on light of ^■ery short wave 

 length." 



If we view the spectrum with the red at our left and the violet 

 at our right, the lengths of the ether waves corresponding to the 

 different colors in the order given by Newton, red, orange, yellow, 

 green, blue, indigo, violet, run from longer to shorter as is the case 

 with the sound waves of the piano from the bass strings at the left 

 to the acute strings at the right. The unit in which to measure 

 these wave lengths most conveniently is the tenth-meter or Ang- 

 strom unit (A) which is lO"!" meters. In terms of this unit the 

 wave length of the extreme red rays at the black Fraunhofer line A 

 of the spectrum is 7,600. That of the violet rays at the extreme 

 right of the spectrum at the black Fraunhofer line H is 3,969. For 

 over one hundred and twenty-five years after Newton's first writing 

 these w^ere tacitly assumed to be the extreme limits of radiation. 

 In ISOO, Sir ^Yilliam Herschel discovered that there were radiations 

 affecting the thermometer outside of the visible spectrum beyond 

 the red, a fact which, however, was received with much skepticism 

 for some time, and his son. Sir John Herschel, forty years later 

 discovered the existence of "cold" Fraunhofer lines in the infra- 

 red, as this region has come to be called. In 1880, Captain Abney 

 by photographic methods of his own devising succeeded in detect- 

 ing and measuring infra-red rays in the solar spectrum as far down 

 as 10,000 A. For this discovery, together wdth certain allied work 

 he was awarded the Rumford INIedal of the Royal Society of Lon- 

 don. Shortly after this (1881) Professor Langley of the Allegheny 

 Observatory, using a newly devised thermometric instrument 

 mvented by him, the bolometer, based on the change in electrical 

 resistance sustained by a platinum strip under changing tempera- 

 ture, demonstrated the existence of an infra-red spectrum (solar) 

 down to 20,000 and later to 55,000 A the Fraunhofer lines in which 

 he mapped to that limit, while detecting the presence of sensible 

 radiation down to 180,000 A. Because of this research he w^as 

 awarded the Rumford Medal of the Roval Societv and, in the 



