x PREFACE 



or I must confess myself the most ungrateful of 

 men receive special mention, and that is my friend 

 Fr. M. Maher, S. J., D.Litt. (Lond.), to whom I owe 

 more than I can express for his kindness in reading 

 my manuscript and supplying me with many most 

 useful suggestions. The figures have been redrawn 

 by my wife for this book. 



BERTRAM C. A. WINDLE. 



QUEEN'S COLLEGE, CORK. In Festo Omn. Anim. 1907. 



