AUTHOE'S PKEFACE. 





I now offer to the public the second edition of a book whose 

 success has far surpassed my expectations. Received with 

 kindness by some, it has been violently attacked by others. 

 It was denounced to the highest representatives of ithe univer- 

 sity authority on which I depended, and I owed my escape 

 from the trouble which might have been drawn on me, because 

 I brought forward a scientific opinion in disagreement with 

 the books attributed to the prophet Moses, to the justice of 

 one of the most honoured members of the Institute. I owe a 

 large debt of gratitude to my illustrious protector. The mind 

 has advanced during six years, and the same troubles will not 

 be met with again. 



A good many alterations will be discovered in this Second 

 Edition ; this is always the case with science. In matters of 

 imagination, when the artist has finished his work, he can 

 cast it on the world and follow his fancy in some other 

 way. If science were only composed of truths, its conditions 

 would almost be the same for its disciples ; but the seeker- 

 after truth is not a creator like an artist, he explains and 

 reflects upon a world of facts, variable at every hour, ac- 

 cording as hypotheses are changed into certainties, or certain- 

 ties of yesterday into doubtful cases of to-day. It is, then, an 

 incessant work of reparation and alteration, in order to main- 

 tain even the most modest work in harmony with the daily 



