470 



Intelligence and Miscellaneous Articles. 



d, thickness of the 



layer of glass 

 already traversed. 



Thickness of the 



absorbing glass 



plate. 



k. 



millim . 

 



millim. 

 1-75 



0-419 



1-85 



1-75 



0207 



5 



1-75 



0-150 



10 



1-75 



0-084 



The absorptive capacity of gas was examined for radiant sources 

 of various temperatures. The number for the temperature 100° 

 can only be considered approximate. 



Temperature of 



the radiating 



body. 



Thickness of the 



absorbing glass 



plate. 



k. 



100 



250 



about 1000 



millim. 

 1-75 



1-75 



1-75 



2-4 



1-47 



042 



Investigation of the Radiation of a Sivan's Lamp at various 

 Temperatures. 

 The radiation of a small Swan's lamp (resistance when cold 80 

 ohms) was also determined when heated by currents of various 

 strengths, from a red heat to a white heat. The currents used were 

 furnished by a Gramme machine, and were measured by means of 

 a differential galvanometer for strong currents. The readings were 

 made by the aid of mirror, scale, and telescope. The numbers in 

 the following table give the readings, and therefore the relative 

 strengths of the current. At the same time the luminosity of 

 the lamp corresponding to the different strengths of current was 

 determined. The following tables were thus obtained : — 



I. Series. 



Strength of 

 current. 



Total 

 radiation. 



Optical 



radiation in 



candles. 



012 



44-5 



87-0 



48-8 



97-0 



0-25 



570 



158-0 



0-70 



67-0 



195 



1-85 



750 



250 



5-4 



88-2 



348 



17-5 



