PREFACE. vii 



even statesmen and historians like Thiers and Guizot in 

 France, and later to Dom Pedro II, in Brazil. The num- 

 ber of his letters is enormous, and until 1842 he kept 

 copies of them all. I know of one of his correspond- 

 ents who received more than one hundred letters from 

 him. To choose among them is not an easy task. Mrs. 

 Agassiz, in the life of her husband, has given a certain 

 number (about ninety), selecting more especially those 

 addressed to Agassiz's mother, father, and brother, and 

 to some well-known men of science, philosophers, phil- 

 anthropists, and politicians ; besides giving letters writ- 

 ten to Agassiz by naturalists like Humboldt, Cuvier, 

 Buckland, Sedgwick, Lyell, etc. Unwilling to repeat 

 what has been already so well done by Mrs. Agassiz, 

 my quotations are limited to letters of Agassiz, 

 addressed to practical naturalists, his contemporaries, 

 working on kindred subjects. To see and appreciate 

 the influence exerted by Agassiz on the progress of 

 palaeontology, geology, and the glacial question, it 

 is important to show his impressions at the very 

 moment when he received them in the course of his 

 studies. 



I have received much information, and copies of let- 

 ters and notes, from persons or families formerly in 

 correspondence with Agassiz. I beg them to receive 

 my thanks ; and I have especially to thank my good 

 friend, M. Auguste Mayor, of Neuchatel, first cousin 

 of Agassiz. Although some years younger than Louis 

 Agassiz, he knew him as a very young man, and fol- 

 lowed closely his eventful and splendid career dur- 

 ing his whole life, both in Europe and in America, 



