168 Prof. Magnus on the Polarization of Heat at 100° C. 



black cloth, was chosen, and stuck for this purpose upon a tin 

 plate and fastened upon the radiating vessel. 



The cloth, as is shown by the following numbers, exhibited 

 no polarization at all ; and herein lies a further proof that the 

 radiant heat comes in part out of the interior of the body, and 

 is polarized at its surface by refraction. 



Table IV. — Radiating surfaces : — rough glass and black cloth. 



Radiating 

 surface. 



Horizontal 

 upwards... 



To the left. 



Horizontal 

 downwards 



To the 



right. 



Analyzing 

 mirror. 



Left 



Horizontal 



Right 



Left 



Horizontal 



Right 



Left 



Horizontal 



Right 



Left 



Horizontal 

 Right 



Mean of all values with perpen- "I 

 dicular planes of reflection... J 



Mean of all values with parallel 1 

 planes of reflection J 



Total heat 



Polarized portion 



Percentage of polarized portion... 



Rough glass. 



mean. 



40-2 



35-3 



38-3 



34-8 



375 



34-5 



38-8 



34-5 



38-7 



34-3 



38 



34-2 



38-6 



34-6 



73-2 

 40 

 5-5 



II. 



mean. 



44-8 



38-7 



42-3 



38-1 



42-6 



371 



43 



37-4 



41-6 



37-3 



42-2 



38 



42-7 



377 



80-4 

 5-0 

 6-2 



Black cloth. 



mean. 



41-5 



417 



39-8 



39-7 



39-7 



39-2 



40 



39-2 



40 



40-5 



38-8 



40 



39-97 



4005 



80-02 

 1-92 



II. 



mean. 



42-5 



41-5 



41-5 



42-9 



41-8 



41 4 



43-4 



41-8 



42-3 



42-25 



41 



41-4 



421 



41-9 



840 

 0-2 



The propagation in the interior of a body to the surface 

 may be regarded as radiation ; but then we must admit that 

 such a radiation takes place in all parts of the inside of ather- 

 manous bodies. It is in fact known that the metals, such as gold 

 and silver, are diathermanous in very thin sheets. This has been . 

 shown by M. Knoblauch for solar heat. For heat of 100° C. 

 and lower temperatures, such as here employed, no observations 

 had been previously made. 



It follows from this investigation, that when heat is propa- 

 gated in the interior of bodies, transverse oscillations take place 

 at every temperature. Or if such oscillations be not linear, they 

 are yet such motions as to have components perpendicular to the 

 direction of propagation, which produce the sa^me effect as rays of 

 heat. 



