X PREFACE TO THE THIRD EDITION 



5. The concluding chapter consists of practical questions 

 and special exercises which necessitate a review by the studen 

 of all that is essential in the book, from a new point of view. 

 It is intended to do for the whole book what the suggestive 

 topics at the end of each chapter may do for the chapters. 



6. The headings of paragraphs are printed in black-faced 

 type, in order to emphasize the analysis of subject matter. 

 Technical terms are in italics the first time they appear. The 

 author does not agree that all technical language should be 

 omitted from even an elementary course. 



The author extends most cordial thanks to the many pub- 

 lishers and authors whose courtesy enables him to reproduce 

 classic illustrations from their copyrighted works. Recognition 

 is given to the sources in immediate connection with the figures. 

 The thanks of the author are also due to many fellow teachers 

 for suggestions and criticisms during the progress of the work, 

 and since the appearance of the second edition. 



T.W. GALLOWAY. 

 JAMES MILLIKIN UNIVERSITY. 



