( 386 ) 



Observations upon the important part which Microscopic Or- 

 ganisms play in the choking up of the Harbours of IVismar 

 and Pillau ; also in the Formation of the Mud which is 

 deposited in the bed of the Elbe^ at Cuxhaven, and upon 

 the agency of similar phenomena in the Formation of the 

 bed of the Nile, at Dongola, in Nubia, and in the Delta of 

 Egypt. By M. Ehrenberg.* 



During the course of the year 1839, M. Ehrenberg made 

 special researches upon the form of the mud-banks in the har- 

 bour of Wismar in the Baltic, and procured the following re- 

 sult, which he communicated to the Society des Amis des 

 Sciences Naturelles, on the 18th of February 1840 : namely, 

 that from l-20th to l-4th of the mass of deposited mud con- 

 sisted partly of living Infusoria, and partly of the empty shells 

 of siliceously enveloped and dead Infusoria. Last year, 1840, 

 he repeated these researches, and obtained a precisely similar 

 result. 



In the harbour of Wismar, according to the documents 

 which were officially communicated by M. Kose, it appears 

 that every week 36 lasts of this mud are deposited, every 

 last weighing 6000 lb. ; so that it may be deduced, after seven 

 and a half months of observation, that there is an annual 

 deposit of 1080 lasts, or of 32,400 metrical cwt., or of 6480 

 cubic metres. For a century, and probably more, matters 

 have proceeded in this way without interruption ; so that 

 during the last hundred years, there has been deposited by the 

 running waters at Wismar 108,000 lasts, equal to 3,240,000 

 cwt, or 648,000 cubic metres of this mud. Hence, then, sup- 

 posing, which is very nearly correct, that 1-lOth of this mass 

 consists of visible organic matter, there has been deposited at 

 Wismar, during the last century, of these microscopic siliceous 

 organisms, 64,800 cubic metres, or annually 648 cubic metres, 

 which, when dry, cannot constitute more than 1-lOth, and 

 probably not more than l-40th or even less of the total weight. 



The results which had been obtained at Wismar in the 



* Report of a memoir read to the Berlin Academy of Sciences in March 

 1841. 



