ACKNOWLEDGMENTS 



To Frederic Burk, president of the San Francisco State 

 Normal School, I am most under obligation in connection 

 with the preparation of this book. His ideas inspired it, 

 and his dynamic criticism did much toward shaping it. My 

 wife, Heluiz Chandler Washburne, gave invaluable help 

 throughout the work, especially in the present revision of the 

 course. One of my co-workers on the Normal School faculty, 

 Miss Louise Mohr, rendered much assistance in the classifi- 

 cation and selection of inferences. Miss Beatrice Harper 

 assisted in the preparation of the tables of supplies and ap- 

 paratus, published in the manual to accompany this book. 

 And I wish to thank the children of the Normal School for 

 their patience and cooperation in posing for the photo- 

 graphs. The photographs are by Joseph Marron. 



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