viii PREFACE. 



of facts. Nevertheless, amongst these facts are some which 

 are indisputable ; also, when we have met with them, we 

 have not hesitated to formulate the conclusions or induc- 

 tions which, resulted from them. We have always done this 

 temperately and with brevity, and without having any other 

 motive than the love of truth. 



We trust that this volume may be read, and that 

 profitably, and that it may awaken, in a large number 

 of its readers, love of and respect for science, namely, that 

 which alone, in these sad times, is at once a refuge and 

 a hope. 



Ch. Letourneau. 



