X PREFACE 



who have aided us with their suggestions. Among our colleagues at 

 West Virginia University who have read portions of the manuscript are: 

 J. G. Leach, C. R. Orton, M. E. Gallegly, R. P. True, W. T. Jackson, 

 B. G. Anderson, R. B. Dustman, and J. H. Hare. In addition, the 

 following have read one or more chapters: B. W. Henry, J. B. Routien, 

 W. D. Gray, and J. B. Conn. We are also indebted to Mrs. H. L. 

 Barnett, who typed most of the manuscript. 



We wish to thank the many individuals, societies, and publishers who 

 have granted us permission to use data and illustrations. Particular 

 acknowledgment is made in connection with the material cited. 



Virgil Greene Lilly 

 Horace L. Barnett 



MORGANTOWN, W. Va, 



May, 1951 



