in the 
ase dif- 
s have 
ing the 
-ording 
elds of 
hysics. 
tor the 
is for 
hoped 
1ensive 
th the 
at cos- 
natural 
hut the 
Amer- 
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at they 
to the 
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1 coun- 
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:nt and 
‘mental 
ACKNOWLEDGMENTS 
HIS study could not have been written without the 
valuable and stimulating suggestions of Professor 
G. P. Adams and Professor F. J. Teggart. Especially 
to the latter I owe a debt which I have not been able to 
acknowledge in direct reference or in quotation marks. 
His books and the personal contact of years have been an 
inspiration for which I take this opportunity to express 
my gratitude. 
In the revision of the manuscript I have received the 
valuable advice and criticism of a number of friends; in 
particular, Miss Lola Jean Simpson and Miss Leona Fas- 
sett. 
rection. 
T S. 
EY.