3 PREFACE. 



language, my diffidence arises from a distrust in my own 

 abilities rather than from the deficient interest of the 

 subject itself, for the history of that literature has re- 

 peatedly proved that natural science can be made more 

 attractive than the products of fiction or mysticism by 

 just as much as the resources of nature exceed the 

 resources of her rivals. 



FELIX L. OSWALD. 



CINCINNATI, March, 1882. 



