138 THE PRESSURE DUE TO RADIATION. 



could be assigned for the repulsion seen in comets, we are now likely 

 to be embarrassed in discriminating between several contributing 

 influences. 



The writers hope to repeat the comet's tail experiment, using smaller 

 spores, if they can be found, and a tube of the new silica glass which 

 will stand stronger heating during the pumping, and thus make it 

 possible to reach higher vacua. 



The Wilder Physical Laboratory, 



Dartmouth College^ Hanover^ N. II., Ajjril., 1903. 



