180 LOUIS AGASSIZ. 



father, in answer to the request contained in 

 one of his last letters that Louis would tell 

 him as much as he thinks he can understand 

 of his work. There is something touching 

 in this little lesson given by the son to the 

 father, as showing with what delight Louis 

 responded to the least touch of parental affec- 

 tion respecting his favorite studies, so long 

 looked upon at home with a certain doubt 

 and suspicion. The whole letter is not given 

 here, as it is simply an elementary treatise on 

 geology ; but the close is not without inter- 

 est as relating to the special investigations on 

 which he was now employed. 



" The aim of our researches upon fossil ani- 

 mals is to ascertain what beings have lived at 

 each one of these (geological) epochs of crea- 

 tion, and to trace their characters and their 

 relations with those now living ; in one word, 

 to make them live again in our thought. It 

 is especially the fishes that I try to restore 

 for the eyes of the curious, by showing them 

 which ones have lived in each epoch, what 

 were their forms, and, if possible, by drawing 

 some conclusions ,as to their probable modes 

 of life. You will better understand the diffi- 

 culty of my work when I tell you that in 

 many species I have only a single tooth, a 



