[hendersonI 



TEMPERATURE GRADIENTS 



75 



40 BO '^0 I60 200 £40 280 3ZO J60 40O 440 



Degrees Centigrade 

 Figure 2 



Convection and Radiation 



The arrangement of the air in layers of density decreasing with 

 height ensured stabihty, the guard ring also being of assistance in this 

 regard. From the agreenient and reproducibility of the observations 

 it was concluded that convection was negligible. The region within 

 the ring was explored horizontally by means of the thermo-element. 

 Within the limit of error no variation could be detected on a horizontal 

 plane over about two-thirds of the width of the ring. Furthermore, 

 tobacco smoke blown into the vessel was observed to settle gradually 

 down to the bottom of the vessel in well defined horizontal layers 

 with no sign of movements due to convection. 



It was necessary however, to make a correction for radiation. 

 The thermo-element, at a temperature intermediate between those of 

 the upper and lower plates, may be receiving more heat than it loses 

 by radiation, consequently its temperature will rise above that of 



