THE PRESSURE DUE TO RADIATION. 



125 



The chang-ing- character of the ga,s action, both with time of exposure 

 and gas pressure surrounding the bahmce vanes, is well illustrated 

 in eig-ht series of static observations in which the glass faces of l)oth 

 vanes weri^ exposed." The results obtained on the two vanes were 

 averaged and plotted us curves in lig. 4, where static deflections due 



Fig. 4. 



to coin1)ined radiation pressure and gas action are shown as ordinates 

 and duration of exposure, in seconds, as abscissa'.^ A liorizontal line 



« Observations were also made on the silver faces, bnt the gas action when the 

 glass faces were exposed was nearly duul)lc that for the i^ilver faces, so the least favor- 

 able case is shown. 



'^Ordinates of the curves arc i)rii]K)rti()nal u> niomeiits. 



