28 INTRODUCTION TO GENERAL SCIENCE 



in a very smooth, highly polished dish. Thus coffee, in a 

 brightly polished pot, keeps warm longer than in a darker, 

 rougher dish. 



References : 



1. 1002 : 390. The Energy Radiated by the Sun. 



2. 1803 : 221-222. Nature of Radiation. 

 a. 1001 : 150-151. Solar Radiation. 



6. 1004 : 166. Radiation from the Sun's Surface. 



c. 1801 : 291-292. Radiation of Heat. 



d. 1802:286-288. Radiation. 



e. 1804:303. Radiation. 



/. 1804 : 416-421. Thermal Effects of Radiation. 



g. 1805 : 327-328. Radiation of Heat. 



h. 1806:306-307. Radiation. 



i. 1807 : 167-170. Radiation of Heat. 



j. 1808 : 218-221. Radiation of Heat. 



Experiment n. Radiation of Heat. 



Apparatus : Two baking powder or spice cans, with labels 

 removed, thermometer, alcohol lamp filled with turpentine 

 (one for the class is enough). 



a. Polish the outside of one can, and smoke the outside of 

 the other can. Fill both with boiling water and place them 

 in the shade and out of a draft. At the end of ten minutes 

 take the temperature of each. State results and explain. 

 Repeat at the end of ten minutes more. 



21. ABSORPTION OF HEAT 



The only kind of heat which is said to be absorbed is radiant 

 heat, or the heat of radiation. Absorption of this radiant heat 

 is not very noticeable except in the case of heat which is re- 

 ceived from the sun. A good radiator is a good absorber. 

 Thus black and rough clothing is warmer than white, if the 



