when an Electron escapes from Surface of a Hot Body. 221 



Summary. 



1. Richardson and Cooke's work on the heating effect 

 has been reviewed, and certain details of relatively secondary 

 importance have been criticised, viz. : — 



(«) The conditions of their experiments were not ideal 

 in the light of later information, and their results 

 are not accurate as regards values of </> for the 

 metals tested. 



(J)) Their experiments on the effects of gas pressure are 

 inconclusive, since they did not get rid of the 

 residual gases, and since the big effects of gases 

 are known to disappear only with the last traces 

 of the residual gases. 



(c) The relationship between the heating and cooling- 

 effects, as tested by Richardson, is shown to be 

 inconsistent with the facts of their experiments. 

 Another relationship applicable to the conditions 

 of their experiments is suggested. 



2. Values of </> for three new materials are given and 

 new values are offered for tungsten. 



3. The complete identification of b with <£ is established, 

 and additional evidence is shown in support of Richardson 

 and Brown's experiments on the kinetic energies of 

 electrons. 



4. It is shown that traces of active gases influence </> in 

 the same way that they influence b, and that traces of inert 

 gases do not affect the value of <£. 



5. It is shown that surface-films formed under the 

 influence of active gases must be ionized, and that the field 

 produced opposes the escape of electrons. The field due to 

 the film is apparently independent of the field due to the 

 applied potentials. 



6. Evidence is offered that intrinsic potential differences 

 do not exist, but that observed contact effects may be 

 attributed to the influence of ionized films. 



7. A new method for determining filament temperatures 

 is described in which the Richardson equation is used and 

 b is determined from measurements on <£>. 



In conclusion, the writer desires to express his in- 

 debtedness to Professor H. L. Cooke for many suggestions, 

 for helpful criticisms, and for continued interest throughout 

 the investigation. 



Palmer Physical Laboratory, 

 Princeton, N.J., 

 February 24, 1915. 



