PRESIDENTIAL ADDRESSES. 557 



essential, and certainly has more to do than merely 

 to telegraph to our eyes to tell us of what the mole- 

 cules and atoms are about. If a first step towards 

 understanding the relations between ether and 

 ponderable matter is to be made, it seems to me 

 that the most hopeful foundation for it is knowledge 

 derived from experiment on electricity in high 

 vacuum ; and if, as I believe is true, there is good 

 reason for hoping to see this step made, we owe a 

 debt of gratitude to the able and persevering 

 workers of the last forty years who have given us 

 the knowledge we have : and we may hope for 

 more and more from some of themselves and from 

 others encouraged by the fruitfulness of their 

 labours to persevere in the work. 



