VI PREFACE. 



Mr. John Evans, Dr. M. Foster, and my brother, Dr. 

 Lubbock, have been so kind as to read through the 

 proofs, and I have to ihauk them for many valuable 

 suggestions. Lord Eayleigh also has been so good as 

 to look at the chapters on Hearing. 



High Elms, Down, Kent. 



