70 Professor G. Forchhammer on the Downs of Denmark, 



borne in with the sea-flood, in many places cover layers of 

 dead fishes, and have thus formed beds of petrifactions similar 

 to those which we find in the older formations. As it appears 

 to be a general law, that the animals which are suddenly de- 

 stroyed in the full vigour of life are more especially preserved 

 as petrifactions, we see here one of the phenomena which may 

 furnish beds of fossil organic remains. The Liimf jord at that 

 time abounded in water-plants, both marine and fresh water, 

 and more especially in Zostera marina, and this vegetation 

 entirely disappeared after the irruption of the sea, in many 

 places because the surface was covered with sand ; and thus 

 was repeated the phenomenon of the older formations so well 

 known in geognosy, where one species of plant indicates a 

 particular bed; and at some future day, when' the beds thus 

 formed shall be rendered accessible by elevations, the period of 

 the irruption of the sea will, in this case, be found marked by a 

 bed of Zostera, and probably by impressions of fresh-water fishes. 

 It is very striking that the Zostera marina, a sea-plant, was even 

 destroyed where there was no covering with sand ; a circum- 

 stance which is probably caused by the very sudden change 

 from the feebly saline condition of the water to its present 

 state. Thus perish the Plaice (Schollen) which are taken near 

 Skagen, when the fishermen attempt to bring them to Copen- 

 hagen in their boats ; whereas the fish of this kind taken thirty 

 English miles farther south, near Frederickshavn, are per- 

 fectly suited to this transport. In a similar way, after the 

 storm of the winter 1839, all the large plaice in the ]L.iim- 

 f jord disappeared, and only quite small, probably young in- 

 dividuals, with a pliable organization, have survived the catas- 

 trophe. It is proved that the Liimf jord was at an earlier 

 time in connection with the sea ; and from this period are 

 derived the vast beds of shells of oysters and of Cardium 

 edule which are found in the Liimf jord. After having, for 

 many centuries, supported no salt-water shells, this bay 

 still supports a great quantity of Mytilus edulis ; and if we 

 could obtain a section of the soil, we would find, first of all, 

 large deposits of Ostrea edulis and Cardium edule, then a layer 

 of Zostera marina^ with fresh-water fishes and probably fresh- 

 water shells, and then again a bed of Mytilus edulis. If, in 



