LETTER FROM HUMBOLDT. 267 



this the better because your text is excellent, 

 full of new and important ideas, expressed 

 with admirable clearness. The charming let- 

 ter (again without a date) which preceded 

 your package impressed me painfully. I see 

 you are ill again ; you complain of congestion 

 of the head and eyes. For mercy's sake take 

 care of your health which is so dear to us. 

 I am afraid you work too much, and (shall 

 I say it frankly?) that you spread your in- 

 tellect over too many subjects at once. I 

 think that you should concentrate your moral 

 and also your pecuniary strength upon this 

 beautiful work on fossil fishes. In so doing 

 you will render a greater service to positive 

 geology, than by these general considerations 

 (a little icy withal) on the revolutions of the 

 primitive world ; considerations which, as you 

 well know, convince only those who give 

 them birth. In accepting considerable sums 

 from England, you have, so to speak, con- 

 tracted obligations to be met only by complet- 

 ing a work which will be at once a monument 

 to your own glory and a landmark in the his- 

 tory of science. Admirable and exact as your 

 researches on other fossils are, your contem- 

 poraries claim from you the fishes above all. 

 You will say that this is making you the slave 



