by a Platinum Surface at High Temperatures. 247 



pated expressed in therms (water-grammes-degrees) per square centi- 

 metre of surface of radiator per second, 

 p = pressure in atmospheres, 



3- = the temperature of the radiator minus the temperature of the 

 enclosure, or in other words the temperature interval in degrees 

 Centigrade. 



The limits between which the formula may be considered to hold 

 good, and the numerical value of the constants for the various gases 

 studied, are given by the following table : — 















The formula holds 



good 





a x 10 5 . 



h x 10 s . 





a. 









and 















from 



to 



from 



to 















3- = 



3 = 



P = 



P = 



Air 



403 



1-63 







•56 



21 



100 



1100 



7 



170 





387 



1-39 







•58 



0-28 



100 



1100 



15 



115 





2705 



1-88 







•35 



-36 



300 



3100 



7 



113 



Mfcrous oxide. . 



276 



1-70 







•74 



0-28 



100 



800 



5 



40 



Carbon dioxide. 



207 



1-50 







•82 



0-33 



100 



1100 



10 



35 



The question as to what proportion of the total loss of heat is due 

 respectively to convection, conduction, and radiation is treated at some 

 length. The influence of experimental conditions, such as the tem- 

 perature of the gas and the dimensions of the radiator and enclosure, 

 is also studied. 



All gases show a rapid increase of the effective conductivity with 

 the pressure. In air, for instance, the rate of cooling is six times 

 greater at 100 atmospheres than it is at atmospheric pressure. The 

 effect of the high rate at which heat is transmitted through compressed 

 gases is discussed, both from a theoretical and a practical point of 

 view, and the bearing of the results on some problems of modern 

 engineering is considered. 



