408 Geological Memoirs, 



arranged according to the law of gravitation. The author states that 

 he has made out, hy direct experiment, that the white, siliceous, 

 infusorial powder by no means retains its white colour, nor does it 

 arrange itself in the same way after being mixed under water with 

 the fine tufaceous ash with which it is interstratified. The hollow 

 cells also of these infusorial cases rise to the surface when mixed 

 with coarse particles, so that some other cause than mere deposit 

 from water must have produced the alternation of fine layers of these 

 with beds of coarse tuff. 



If it should be said that these coarser particles of tuif, amongst 

 the fine layers of infusorial animalcules, consist of concretions which 

 have formed in water from the more minute particles since the mass 

 was deposited, or that they have been formed at all by aqueous 

 action, the association with volcanic crystals, sometimes of consider- 

 able size, renders such an explanation impossible. In the same way 

 it seems impossible to account for the appearance by supposing that 

 the masses containing infusoria were deposited regularly in alter- 

 nation with deposits of tuff, because the internal structure and com- 

 position of the tuff itself, and the fact that it is often partly and 

 sometimes almost entirely made up of similar organic bodies, is 

 directly opposed to such a view. 



But again, it may be imagined that the infusorial animalcules were 

 introduced after the volcanic deposits had been effected, and partly 

 by aqueous action. To this idea, however, is opposed the fact of 

 their being almost always in fragmentary condition, and in great part 

 metamorphosed, — an appearance which the author has never seen in 

 the rapidly forming beds of these animal remains, either in Berlin or 

 in the Luneburg forest, or near Eger, however thick the deposits may 

 be. The regular stratification and distinctly arranged appearance 

 are also opposed to this view; and indeed it becomes altogether 

 impossible, when we consider the mingling that there is of Phytoli- 

 tharia — the siliceous particles of certain minute vegetable bodies— 

 which could as little form and increase in these places, or even pene- 

 trate to them, as the bones of quadrupeds. 



5. The Loss in the Rhine neighbourhood appears quite distinct 

 from the tuff, although it contains parts made up of organic bodies. 

 It bears no appearance of having undergone the action of heat. 



