PREFACE TO THE SECOND EDITION. 



THIS second edition, in preparation for three years, has been the 

 subject of a careful revision and of numerous alterations. 



Some very notable improvements upon the first edition have been 

 made. 



A new plate upon the age, and fifty-three original figures, have 

 been added. 



The matter, while much condensed as a whole, has in many places 

 been rewritten at great length. 



Finally, by the employment of three varieties of type, we are 

 enabled to indicate the degree of importance of each subject treated, 

 and to facilitate the use of the volume to those who can consult only 

 the essential parts. 



ARMAND GOUBAUX, GUSTAVE BARRIER. 



ALFORT, March 1, 1890. 



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