178 



Prof. R. W. Wood and Mr. S. Okano on 



not appear to have been investigated up to the present time* 

 A resume of our results was presented at the annual meeting 

 of the American Philosophical Society in May. 



In the majority of our experiments we have used bulbs 

 made of the new pyrex glass manufactured by the Corning Co. 

 This glass shows much less discoloration from the action of 

 sodium vapour at high temperatures than any of the glasses 

 which have been on the market heretofore, and on account 

 of its very low expansion coefficient requires little or no 

 annealing, being almost as satisfactory as fused silica in this 

 respect. It can be obtained in the form of tubing of all 



Fig. 1. 



sizes, flasks of various forms, beakers, &c. ; consequently it 

 is possible to make very elaborate apparatus with little 

 difficulty. The apparatus with which the minimum ionizing 

 potential of sodium was measured is shown in fig. 1. 



