Preface 9 



Director of the Government Laboratory, Sir Ronald 

 Ross, Sir Frank Dyson, Sir John Snell, Sir Charles 

 Parsons, Sir Daniel Hall, and Sir Joseph Petavel, Director 

 of the National Physical Laboratory. 



The facilities given us include permission to quote from 

 published works in compiling some of our chapters, and 

 for this additional help we make grateful acknowledg- 

 ment. 



It may be said that this volume is published with the 

 authority and consent of many of the distinguished 

 scientists whose achievements it relates. We hope their 

 kindly assistance will be justified by the interest the book 

 will awaken in those who are eager to know more of the 

 notable conquests of Science in our own day. 



T. C. Bridges 



H. Hessell Tiltman 



