PREFACE. 



Were I to say, ^' this is a very interesting little book/' 

 many would conclude that I was nearly allied to a well- 

 known bird, whose mouth is so often filled with the praise 

 of its own beauty. And yet T might say so without the 

 slightest vanity; for I shine by borrowed light, and for 

 nearly all that is interesting in the book I am indebted to 

 my talented scientific friends and precursors. I have been 

 like the bee — not making, but gathering honey. Like 

 the bee, I have formed the cells, and had I been able to 

 equal her in skill, I might well have been pleased with my 

 workmanship. But though inferior in skill, I have not, 

 during the progress of the work, been inferior to her in 



