94 Anniversary Address by Lord Rayleigh. 



to extend these enquiries ; and the results already obtained are of great 

 importance, both from a theoretical and from a practical point of view.. 

 De Vries' work has exercised considerable influence on other branches of 

 biology, and has suggested new lines of investigation in many directions. 



Mrs. W. E. Ayrton is the recipient of the Hughes Medal, which is awarded 

 for original discovery in Physical Sciences, particularly electricity and 

 magnetism, or their applications. Her work on the Electric Arc has been 

 described in a paper published in the ' Philosophical Transactions/ and in. 

 various other publications. 



Mrs. Ayrton's investigations cover a wide area. She discovered the 

 laws connecting the potential difference between the carbons of an arc with 

 the current and with the distance between them, and proved these to apply 

 not only to her own experimental results but to all the published results. 

 of previous observers. Dealing with the modifications introduced into the 

 arc by the use of cores in the carbons, she found the causes of these- 

 modifications. The peculiar distribution of potential through the arc was. 

 traced, and its laws were discovered by her. 



Having found the conditions necessary for maintaining a steady arc, and 

 for using the power supplied to it most efficiently, she was able to explain 

 the cause of " hissing," and the causes of certain anomalies in the lighting; 

 power of the arc. 



Eor the past four years Mrs. Ayrton has been engaged in investigating, 

 the causes of the formation of sand ripples on the seashore. 



