306 ON THE DISPERSION IN ARTIFICIAL DOUBLE REFRACTION. 



In conclusion the author wishes to express his most grateful thanks for the 

 assistance which has been rendered him by the Royal Society, without which this 

 work could not have been undertaken. He desires also to place on record his 

 indebtedness to Professor F. T. TROUTON, F.R.S., who has most generously placed the 

 resources of the Physical Laboratory of University College, London, at his disposal ; 

 und also to Mr. A. W. PORTER, B.Sc., whose interest in the work and kindly criticisms 

 and suggestions have been invaluable. 



