vi PREFACE 



cepted by the author of the original paper. The index was made 

 on the basis of these brief notes and hence cannot be relied on 

 to indicate all the papers on a subject that appear in the literature 

 list. The appendix is for the convenience of a limited class of 

 readers. 



The author expresses his sincere thanks to Professors F. E. 

 Bartell, E. G. Conklin, I. H. Derby, G. A. Hulett, A. F. Kovarik, 

 E. P. Lyon and others for examining the copy or parts of it and 

 offering suggestions, and to Margaret S. McClendon for assist- 

 ance in its revision. 



J. F. McClendon. 

 Minneapolis, October I, 1916. 



