The editors and the respective authors of the 

 Twentieth Century Text Books have been chosen 

 with reference to their qualifications for the special 

 work assigned to them. These qualifications are, 

 first, that the author should have a thorough knowl- 

 edge of his subject in its latest developments, espe- 

 cially in the light of recent educational discussions ; 

 second, that he should be able to determine the 

 relative importance of the subjects to be treated 

 in a text book ; third, that he should know how to 

 present properly his topics to the ordinary student. 



The general editorial supervision of the series 

 has been placed in the hands of Dr. A. F. Night- 

 ingale, Superintendent of High Schools, Chicago, 

 and Professor Charles H. Thurber, of the Univer- 

 sity of Chicago, men thoroughly conversant with 

 every phase of education. 



The offer of a complete series of text books for 

 these higher grades of schools, issued under auspices 

 so favorable, concentrating and co-ordinating such a 

 force of able writers all working with one end in view, 

 is an event worthy of the twentieth century, and a 

 good omen for the educational welfare of the future. 



Nearly one hundred volumes are in prepara- 

 tion, and several are now ready. Others will 

 follow rapidly, the issue of which will be duly 

 announced. 



D. APPLETON AND COMPANY, NEW YORK. 



