ENCEOACHMENTS OF TIIE SEA. 661 



fresli-water fish previonslj inhabiting tliis lagoon, which was 

 famous for its abundant fisheries. Millions of fresh-water fish 

 were thrown on shore, partly dead and partly dying, and were 

 <jarted off by the people. A few only survived, and still frequent 

 the shores at the mouth of the brooks. The eel, however, has 

 gradually accommodated itself to the change of circumstances, 

 and is found in all parts of the fjord, while to all other fresh- 

 water fish the salt-water of the ocean seems to have been fatal. 

 It is more than probable that the sand washed in by the irruption 

 covers, in many places, a layer of dead fish, and has thus prepared 

 the way for a petrified stratum similar to those observed in so 

 many older formations. 



" As it seems to be a law of nature that animals whose life is 

 suddenly extinguished while yet in full vigor, are the most likely 

 to be preserved by petrification, we find here one of the conditions 

 favorable to the formation of such a petrified stratum. The bot- 

 tom of the Liimfjord was covered with a vigorous growth of 

 aquatic plants, belonging both to fresh and to salt-water, espe- 

 cially Zostera marina. This vegetation totally disappeared after 

 the irruption, and in some instances was buried by the sand ; and 

 here again we have a familiar phenomenon often observed in an- 

 cient strata — the indication of a given formation by a particular 

 vegetable species — and when the strata deposited at the time of 

 the breach shall be accessible by upheaval, the period of irruption 

 will be marked by a stratum of Zostera^ and probably by impres- 

 sions of fresh-water fishes. 



" It is very remarkable that the Zostera Tnarina, a sea-plant, 

 was destroyed even where no sand was deposited. This was 

 probably in consequence of the sudden change from brackish to 

 salt-water It is well established that the Liimfjord com- 

 municated with the German Ocean at some former period. To 

 that era belong the deep beds of oyster-shells and Cardium edule, 

 which are still found at the bottom of the fjord. And now, after 

 an interval of centuries dming which the lagoon contained no 

 salt-water shell-fish, it again produces great numbers of Mytilus 

 edulis. Could we obtain a deep section of the bottom, we should 

 find beds of Ostrea edulis and Cardium edule^ then a layer of 

 Zostera marina with fresh-water fish, and then a bed of Mytilus 

 edulis. If in course of time the new channel should be closed, 



