SCIENCE PROGRESS 



IN THE TWENTIETH CENTURY 



A QUARTERLY JOURNAL OF 



SCIENTIFIC WORK 



& THOUGHT 



NO. 23. JANUARY 191 2 



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. 



1912 



Price 5/- net 



vol. VI 



