152 LOUIS AGASSIZ. [CHAP. vii. 



dermes fossiles de la Suisse," containing spatangoids and 

 clypeastroids, appeared during the autumn of 1839, in 

 the " Nouveaux Memoires de la Societe Helvetique." 

 Until then no publication on echinoderms of such impor- 

 tance in regard to classification, correctness of localities, 

 and stratigraphical position, had appeared. Gressly had 

 had a great share in it, having found the majority of the 

 specimens used, and having helped Agassiz in his descrip- 

 tions and other details of each species. A special artist, 

 Dickmann, was trained by Agassiz to draw Echinidae, and 

 the accompanying plates are excellent. The memoir was 

 made use of at once, with great advantage, by all geolo- 

 gists studying the Jurassic and Neocomian series ; and 

 seldom has such an important and timely contribution 

 to palaeontology been made. The second part, " Cida- 

 rides," soon followed, in June, 1840; and the whole 

 work is one of Agassiz's best, being remarkably clear, 

 with excellent classification, good genera and species ; 

 all of which have been accepted and used since, in all 

 the works on fossil echinoderms. 



At the beginning of the winter Agassiz wrote a very 



r 



interesting letter on the glaciers to Elie de Beaumont, 

 asking him to communicate it to the Academy of Science. 

 But de Beaumont was a rather unfair opponent in 

 everything relating to the glacial question, and he did 

 not read the letter to the Academy, as he was requested 

 to do. As it is important, and allows every one to see 

 the opposition at that time constantly made against the 

 doctrine of the action of glaciers in the Alps, I give it 

 almost in full, suppressing only local details relating to 



