SCIENCE PROGRESS 



IN THE TWENTIETH CENTURY 

 A QUARTERLY JOURNAL OF 

 SCIENTIFIC WORK 

 & THOUGHT 



VOL VII 

 NO. 27. JANUARY 191 3 



EDITORS 



H. E. ARMSTRONG, Ph.D., LL.D., F.R.S. 

 J. BRETLAND FARMER, M.A., D.Sc, F.R.S. 



LONDON 

 JOHN MURRAY, ALBEMARLE STREET, W. 



l 9 l 3 



